Eighth Grazing Lands Forum

An Explosion in Slow Motion: Noxious Weeds and Invasive Plants on Grazing Lands

Welcome and Introduction to GLF Robert Lucey, GLF President, Cornell University

Overview: Motivation and Science Janette Kaiser, Forest Service, USDA (moderator)

Overview: Status and Policy Faith Campbell, Natural Resources Defense Council (moderator)

Luncheon--Agricultural Chemicals, Weed Control, and National Legislation Ralph Heimlich, GLF First Vice President, Economic Research Service, USDA (introduction)

Working Tools:

The Science and Technology of Weed Management Ken Krupa, Economic Research Service, USDA (moderator)

Panel Discussion--Working arrangements, approaches, and institutions that have achieved success in addressing and controlling noxious weed and invasive plant infestations on grazing lands through integrated approaches. Greg Hendricks, GLF Second Vice President, Soil Conservation Service, USDA (moderator)

SPECIAL REPORT TO GLF:

The Grasslands and Rangelands Coalition: Partners in Research and Education that Benefits Society David B. Hannaway, Oregon State University

An Explosion in Slow Motion: Noxious Weeds and Invasive Plants on Grazing Lands

Concerns about the effects of invasive alien plants and noxious weeds are intensifying across a wide variety of interests. This is evident in the heightened level of state and federal agency action, legislative activity, and public pressure for more research and resources to effectively deal with the problem. Unmanaged weed populations are increasingly threatening the integrity of grazing lands, reducing land values, crowding out native plant habitat, changing wilderness areas, and reducing crop and forage production. Weeds know no ownership boundaries. To most effectively deal with the issue requires improving common understanding and a high degree of coordination and cooperation across land ownerships. GLF's program was designed to motivate interest in this problem and explore technical and institutional, and organizational solutions.

How Do Weeds Affect Us All?--Dr. George Beck set the stage for the day, painting a broad picture in terms of the breadth and depth of this issue. Dr. Beck helped all participants become aware of the relevance weeds have in our everyday lives and the common ground we share regarding this issue. Participants gained an understanding of the threat weeds pose to the health and sustainability of both cropland and native ecosystems, including:

• What's a weed?
• Impacts on:
  • soil stability
  • water quality
  • wildlife forage and habitat
  • cropland and forage production
  • economics
  • species diversity, now and in the future
  • plant succession dynamics
  • native plant habitat
  • wilderness areas
  • open spaces
  • human health

How Weeds Spread--Dr. John Randall set the stage by describing the ecology and dynamics of plant communities; how communities are influenced by physical settings, climate and disturbance, including human uses. This presentation provided background for understanding unwanted plant introduction, invasion, and spread. Dr. Randall discussed differences in modes of infestation between disturbed and undisturbed ecosystems.

Biological Pollution:

An Historical Perspective--Dr. Randy Westbrooks gave the audience an understanding of the history of weed infestations in the U.S., conveying an historic perspective and the urgency of this "explosion in slow motion". Using a unique timeline perspective, Dr. Westbrooks helped participants become aware of pathways of introduction that have been used by various species. Participants gained an understanding of the consequences and opportunities regarding weed management.

Legislation and National Strategy--Dr. Howard Singletary described existing Federal statutes, with emphasis on the Federal Noxious Weed Act [7 U.S.C. sections 2801-2813], the 1990 Food, Agriculture, Conservation, and Trade Act [FACTA; 7 U.S.C. section 2814(e)(7)], and Executive Order 11987. He described weaknesses in present programs, both in the statutes themselves, their execution, and funding. Problems encountered in applying the Federal Noxious Weed Act were discussed, including:

• The definition of noxious weeds (Section 2(c));
• Absence of emergency authority to prohibit the entry of foreign weeds which meet the definition of a Federal noxious weed, but have not been added formally to the list;
• Unclear authority to prohibit the intentional movement of Federal noxious weeds across State lines, including exclusion of nursery and bird seed industry shipments;
• Exclusions of seeds and seed certification.

The impact of current funding constraints and variations from year to year in implementing both the Federal Noxious Weed Act and the 1990 FACTA were explored, including lack of funding for research for adequate control methods. Dr. Singletary went on to describe bills to amend the Federal Noxious Weed Act, their status in Congress, and the Administration's position. This presentation provided information to participants regarding key decision-makers in Congress and the Administration, organizations that are actively working on the issue, and other paths to press for improvements.

Luncheon Address:

Agricultural Chemicals, Weed Control, and National Legislation--Dr. Ray McAllister shared his personal and professional perspectives on controlling noxious weeds, emphasizing the need for an integrated approach that uses all potential control methods within the context of a comprehensive regional program cutting across all private and governmental landownerships. Dr. McAllister went on to outline upcoming legislation that could affect the ability to use weed control chemicals on grazing lands, including reauthorization of the Clean Water and Safe Drinking Water Acts, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and the Endangered Species Act.

Working Tools:

The Science and Technology of Weed Management-- Dr. Scott Glenn cataloged the types of tools available for weed management, including human hand weeding, animal grazing, mechanical methods, herbicides, natural biological control agents, and competitive plants. The pros and cons of each method, including costs, effectiveness, and environmental externalities, were discussed. The concepts of combining tools via integrated pest management (IPM) was thoroughly explored. Dr. Glenn briefly speculated on possible weed management tools of the near-term future, including plant sterility agents, species- specific pesticides, genetic alteration, and introduction of superior forage-producing strains of grazing plants. Developing information/infrastructure management tools, such as government interagency computer linkages and new check-point monitoring and detection devices at border and public land entrances to deter the introduction and spread of weeds, was raised. The types of academic research, funding levels, and possible sources of funding needed to implement a regional or national weed strategy were also addressed.

Panel Discussion--A panel of five presenters from diverse regional and professional backgrounds offered their perspectives on working arrangements, approaches, and institutions that have achieved success in addressing and controlling noxious weed and invasive plant infestations on grazing lands through integrated approaches. The panel was comprised of Dr. Tim Butler, Dr. John Randall, Dr. Richard Malecki, Mr. Charles Jarecki, and Dr. George Hittle, moderated by Greg Hendricks. The speakers explained what motivated their organizations to address this issue, and described the organization's membership and operating procedures, including ties with other organizations and State and Federal agencies. Methods for noxious plant management used by the organization were outlined. Lessons learned from both successes achieved and failures of efforts attempted were drawn and barriers to effective action that need to be addressed were identified.

U.S. Congress, Office of Technology Assessment

Phyllis N. Windle, Project Director for the U.S. Congress, Office of Technology Assessment study provided copies of a report brief and report summary of their new report, released in September, 1993. The OTA report documents 4,500 non-indigenous species (NIS) of foreign origin that have established free-living populations in the United States. At least 15 percent of the species identified trigger severe harm, and just 79 caused documented losses of $97 billion in control costs and losses of marketable goods.

The OTA report stresses that prevention is the best strategy, but recognizes that "zero entry" is an unrealistic goal. Integrated control programs that use available chemical pesticides, biologically based measures, and genetic engineering remain a necessary part of NIS management.

OTA criticizes Federal NIS policy as a "largely uncoordinated patchwork of laws, regulations, policies and programs," noting that at least 20 agencies are involved. Federal laws leave obvious and subtle gaps, which most States do not fill. OTA's report discusses needs for a more stringent national policy, better management of NIS fish, wildlife, and diseases, growing problems with NIS weeds, damage to natural areas, education, emergency action, funding, and gaps in legislation and regulation. Options for Congressional action are raised and their pros and cons discussed.

Copies of the 391 page full report can be ordered from:

Many definitions of weeds have been created and historically, all definitions are centered around human activities. For example, the Weed Science Society of America defines a weed as 'a plant out of place'; Emerson in 1978, thought a weed was 'a plant whose virtues have yet to be discovered'; and Torrell defined a weed as 'a plant that interferes with the management objectives of a given area of land at a given point in time'. Anthropomorphic definitions of weeds are not inherently bad as humans evolved on earth and we use our natural resources and weeds are plants that inhibit our efficient use of natural resources. However, there are physiological and biological characteristics of the group of plants that we call weeds and careful examination of these factors will help one to better understand why weeds are problematic.

Grime (1979) indicated that two basic external factors limit the amount of plant material found in any given environment; i.e., stress and disturbance. Stress includes environmental phenomena that reduce production such as limiting light intensity, water availability, nutrients, or optimal temperatures for growth. Disturbance is the partial to total disruption of plant biomass typically caused by fire, flooding, mowing, tillage, grazing, etc. If one considers the four extremes of stress and disturbance (e.g. high and low stress v. high and low disturbance) four outcomes for plant production ensue. Plant death occurs under high stress and high disturbance; the development of a population of stress tolerators occurs under high stress and low disturbance; a population of ruderal plants establishes under low stress and high disturbance; and competitor species dominate under low stress and low disturbance. Thus, in an environment limited by abiotic (physical factors such as climate, fire, flooding, etc.) and biotic (insect predators, plant pathogens, plant competition, etc.) factors, three evolutionary strategies for plants occur. Stress tolerators are those plants that reduce allocations to vegetative growth and reproduction to ensure a population of relatively mature individuals in a limiting environment; competitors maximize resource capture in productive but relatively undisturbed environments; and ruderals are plants with short life cycles and high seed output that are found in highly disturbed environments and occupy the early stages of secondary succession. Few plants fall into these extreme categories and most are combinations of the three evolutionary strategies. Many herbaceous annual, biennial, and perennial weeds can be characterized as competitive ruderals. These plants occupy sites where dominance by true competitors does not occur because of disturbance; occasional disturbance is expected but frequent or severe disturbance would favor ruderal plants.

Environments favoring competitive ruderals would include meadows, seasonal grasslands, rangeland subject to seasonal disturbance (e.g. grazing), floodplains, eroded areas, lake and ditch margins, and arable lands. Thus, most weedy species occupy land in early to intermediate stages of secondary succession.

Weed Impacts; So What's the Big Deal?

Noxious weeds are typically plants of foreign origin and thus, did not evolve in North America. When these plants were inadvertently or otherwise imported into the United States, biotic factors, such as insect predators and plant pathogens, that evolved with the weed at its points of origin were not imported. Thus, in their 'new home', alien plant populations are regulated only by abiotic factors and this is not enough to keep their populations from increasing exponentially. For example, leafy spurge (Euphorbia esula) was introduced into the Red River Valley of North Dakota and Minnesota in the 1880's and this plant infests over 1 million acres in North Dakota alone today (Lacey et al., 1985). Spotted knapweed (Centaurea maculosa) was introduced into Gallatin County, Montana in the 1920's; by 1984 it had spread to all 56 Montana counties occupying over 2 million acres and today, over 4.7 million Montana acres are infested with this weed (Lacey et al., 1986). Yellow Starthistle (Centaurea solstitialis) was introduced into California in 1869 near Oakland; by 1965 over 1.9 million acres were infested with yellow starthistle and by 1985, infestations increased to 7.9 million acres (Thomsen et al., 1989). Purple loosestrife (Lythrum salicaria) infestations were studied from 1965 through 1978 at the Montezuma National Wildlife refuge in New York and biomass yield of purple loosestrife increased over this time from 0 percent of that harvested in 1965 to 90 percent in 1978 (Thompson et al., 1987). A recent study in Colorado assessing the encroachment of Dalmatian toadflax (Linaria genistifolia spp. dalmatica) on rangeland showed over 4 years that this weed increased 322 percent in cover, 1250 percent in shoot density per acre, while crested wheatgrass cover decreased 172 percent (K.G. Beck unpublished data, Colorado State University, Ft. Collins).

We have significant alien plant infestations occupying rangeland and other natural resource areas in the United States and Canada today. Spotted knapweed occupies over 7.2 million acres in nine states and 2 Canadian provinces (Lacey, 1989). Diffuse knapweed (Centaurea diffusa) occupies over 3.2 million acres in 10 states and 2 Canadian provinces (Lacey, 1989). Russian knapweed (Acroptilon repens) occupies over 1.4 million acres in 9 states and 2 Canadian provinces (Lacey, 1989). Yellow starthistle occupies over 9.4 million acres in 10 states and 2 Canadian provinces (Lacey, 1989; Maddox and Mayfield, 1985). Leafy spurge infested over 2.5 million acres in 30 states in 479 U.S. counties as of 1979 (Lacey et al., 1985). Downy brome or cheatgrass (Bromus tectorum) infests over 101 million western U.S. acres and is listed as the dominant plant in the Intermountain West (Mack, 1981). A recent article in the Atlantic (Devine, 1993) laments the displacement of native bunchgrasses from downy brome encroachment in the west.

Cropland and forage production impacts:

In 1984, the average annual yield loss in 64 U.S. and 36 Canadian crops caused by weeds was $7.4 billion and $909 million, respectively (WSSA, 1984). Leafy spurge reduces the cattle carrying capacity of rangeland in North Dakota and Montana by 75 (Thompson et al., 1990) and 63 percent (Bucher, 1984), respectively. Forage losses in Montana from spotted knapweed infestations were valued at $4.5 million in 1984 and if spotted knapweed continues to spread in Montana at its current rate, at least 33 million acres will be infested by 2009 causing $155 million in annual forage losses (Bucher, 1984).

Soil stability and water quality impacts:

Soil and water losses have occurred and continue to occur on millions of acres where grass communities have been replaced by tap-rooted plants. Lacey et al (1989) measured surface water runoff and sediment yield (soil erosion) during a 30 minute simulated rainfall event on spotted knapweed dominated rangeland compared to native bunchgrass dominated sites. They found surface water runoff and soil erosion were 56 and 192 percent higher, respectively, on spotted knapweed dominated sites. This indicates that the presence of spotted knapweed on Montana rangeland is detrimental to soil and water resources. Soil on spotted knapweed dominated sites is eroded to a much higher degree compared to bunchgrass communities and water infiltration into the soil profile is less. This could and most likely has contributed to the displacement of native grasses because soil-water relationships have been altered due to the presence of spotted knapweed. This equates to greater sedimentation of streams, rivers, and lakes and will negatively impact fisheries.

Wildlife forage and habitat impacts:

The influence of noxious weeds on wildlife is not well understood or documented, but a few facts exist and the impact appears mostly to be detrimental. In western Montana, elk (Cervus canadensis) use of rangeland was estimated by counting pellet groups and there were 1575 pellet groups per acre in bunchgrass sites compared to 35 pellet groups per acre in spotted knapweed dominated sites (Hakim, 1975). Several studies indicated that spotted knapweed was not found in elk diets (Kufield, 1973;Lovaas, 1958;Mackie, 1970;Morris and Schwartz, 1957;Stevens, 1966). However, a recent study by the University of Montana indicates that elk grazed spotted knapweed in early winter, but in late winter, their diets were primarily grasses (Bedunah and Carpenter, 1990). Little to no spotted knapweed was found in their diets during February, March, or April even though the study area was dominated by spotted knapweed. Elk and deer eat spotted knapweed seedheads in winter and rosettes leaves in spring in the Bitteroot Valley of Montana; however, they may do so because of availability and not because of preference. In another study, spotted knapweed was common on mule deer (Odocoileus hemionus) range in Montana although the plant was not detected in their diets (Guenther, 1989). A game damage survey to alfalfa was conducted in 1986 in northeastern Wyoming, an area badly infested with leafy spurge; feces were examined histologically to determine which plant species were being consumed and they found no leafy spurge in deer diets. In North America, purple loosestrife encroaches upon and displaces desirable food plants and waterfowl nesting sites (Thompson, 1987). Cattails (Typha latifolia) were displaced by purple loosestrife competition, exacerbated by the selection pressure placed on cattails by muskrat feeding; and when these sites are dominated by purple loosestrife, muskrats move out. Purple loosestrife infestations make waterfowl broods more susceptible to predation because of the increased cover provided by tall purple loosestrife and the lack of a direct route from water to nesting sites. Certain waterfowl species, e.g. canvasback (Aythya valisineria) and black tern (Chlidonia niger) prefer to nest on relatively open sites such as abandoned muskrat nests built from cattails. With purple loosestrife encroachment and displacement of cattails and other riparian plants that provide these sites, suitable nesting sites are decreased.

Noxious weeds are not entirely harmful to wildlife. A Montana Outdoors article indicates that weeds provide cover, habitat diversity, and a source of feed for many game and non-game birds (Wiegand, 1977). It is worth noting however, that the tendency of noxious weeds to form monocultures would decrease habitat biodiversity once this occurred. In British Columbia, knapweed rosettes were found to be important components in the diets of deer and elk in early spring (Miller, 1990). A recent study in Colorado and Wyoming indicates that three times as many small mammals frequented Russian knapweed infested rangeland compared to adjacent non-infested sites (R. Olson, University of Wyoming, personal communication). Adaptation occurs as evidenced by one small mammal, a harvester mouse, using the Russian knapweed infested sites and this mammal may serve to spread the weed as they cache seeds.

Species diversity and impact on native plant habitat:

Many noxious weeds dominate plant communities and tend to form monocultures and this obviously negatively impacts native biological diversity in the United States. Downy brome communities in the Intermountain West are poor in species composition compared to steady state (climax) sagebrush/bluebunch wheatgrass (Artemisia tridentata/Agropyron spicatum) communities (Rickard and Cline, 1980). Displacement of native plants by spotted knapweed was assessed in Glacier National Park in Montana from 1984 through 1987 (Tyser and Key, 1988). These sites were originally classified as Idaho fescue (Festuca idahoensis) and rough fescue (Festuca scrabella) dominated plant communities. Spotted knapweed impacts to native plant communities were assessed on perimeter, fringe, and core weed infestations. These researchers found the species richness gradient to be inversely proportional to spotted knapweed stem density; i.e., the more spotted knapweed stems per unit area, the fewer number of plant species present. Species richness declined as one moved along the transects from the perimeter to the core infestations (species richness ranked perimeter>fringe>core). Spotted knapweed stem density was the only variable associated with the species richness effect. These researchers further classified plants in the fringe infestations as common, uncommon, or rare. Of the 38 species evaluated in 1984, 31 were reclassified at the same frequency in 1987. However, seven of the original species were reclassified into lower frequency categories in 1987 (Galium boreale, Hieracium umbellatum, Potentilla arguta, Potentilla gracilis, Silene parryi, Stipa occidentalis, and Tragopogon dubuis - note the last species was an uncommon, weedy, alien). Six species were classified as common in 1984 and five of these remained in this category in 1987. Of the 21 uncommon species in 1984, only 16 remained as such in 1987 with six being reclassified as rare in 1987. Additionally, five rare and two uncommon species found in 1984 were not present in 1987 (Agropyron spciatum, rare; Castilleja cusickii, rare; Collomia linearis, rare; Heuchera cylindrica, rare; Lithospermum ruderale, rare; Stipa occidentialis, uncommon; and Tragopogon dubius, uncommon and alien). Additionally, native plants are being displaced in Utah by dyer's woad (Isatis tinctoria) (West and Farah, 1989) and in California by yellow starthistle (Maddox and Mayfield, 1985).

The impact of noxious, alien weeds on rangelands and other natural resource areas are not well understood nor documented. The weed science community has spent a lot of time learning how to control weeds v. understanding their biology, ecology, and impacts. This trend is changing and with increased opportunities for grant supported research in these areas, a greater understanding will occur. Nonetheless, aggressive, alien plants will continue to displace native plants in their habitats primarily due to a lack of biotic pressure placed on alien plant populations (no biological control - in the absence of other control measures). This is further exacerbated by the rapid rate of spread by alien weedy species and the difficulty associated with effectively managing all infestations in any given year because infestations are very large and scattered across landscapes.

Open space and wilderness area impacts:

Open spaces are prime areas for alien plant invasion. Open spaces associated with cities and counties typically are former grazingland or abandoned farmland. Thus, open spaces have been disturbed to one degree or another and subject to secondary succession - weed invasion. Open space infestations serve as sources for new infestations on adjacent land and land farther away. For example, open spaces along Colorado's Front Range communities are dominated by alien plants. Boulder City and County Open Space ground is infested with diffuse knapweed, spotted knapweed, Russian knapweed, Canada thistle, field bindweed (Convolvulus arvensis), Dalmatian toadflax, downy brome, and musk thistle; Cherry Creek State Park in the greater Denver Metropolitan area is badly infested with diffuse knapweed, leafy spurge, musk thistle, Canada thistle, and field bindweed and these infestations are spreading along Cherry Creek into the South Platte River which flows into Nebraska; Fort Collins open space areas are infested with leafy spurge, Canada thistle, musk thistle, diffuse knapweed, field bindweed, downy brome, puncturevine (Tribulus terrestris), and these plants are particularly troublesome along the Poudre River corridor which flows into the South Platte, thus, these infestations are spreading into Weld, Morgan, Logan, and Sedgwick Counties in Colorado and into Nebraska.

Backpackers and horsepackers inadvertently spread alien plants into wilderness areas. Seeds on clothing, packs, animals, or in contaminated hay brought into wilderness, or excreted in feces by domestic animals, are sources for new infestations. For example, the Rawah Wilderness in Colorado is infested with musk thistle and it is spreading rapidly because of the plant's biology and lack of weed management input. Canada thistle infestations in Rocky Mountain National Park have been the object of interest for the past 3 years. Infestations started along horse and foot trails and have spread from there into native plant communities (T. Mclendon, Colorado State University, personal communication). Dry, upslope conditions, thick canopies from woody species, and well-established grass meadows (especially wet meadows) inhibited Canada thistle invasions. Canada thistle populations appear to thin with time and become part of the plant community in many instances, in the absence of further disturbance. However, even minor disturbance from elk grazing promoted Canada thistle invasion and establishment into grasslands.

Plant succession dynamics impacts:

Weeds (alien or native) would be classified under 'natural systems' as pioneers, invaders, or increasers. Disturbance creates an opportunity for secondary succession to occur and weeds will occupy the site initially. Depending upon the degree of disturbance, annual weeds will occupy the site first and be replaced with time by herbaceous perennial weeds. In abandoned farmland, the systematic replacement of early and intermediate plant seral stages occurs over time until a steady state community develops - not necessarily identical to the pristine community before farming was practiced; this is termed old field succession. The time associated with these changes varies with climate, soil nutrient status, weed species present, availability of native plant propagules and species composition thereof.

The impact of noxious weeds on plant succession dynamics of grazinglands is not well understood. Patches of noxious weeds, such as leafy spurge or Russian knapweed, survive for extended periods. For example, a Russian knapweed stand in Saskatchewan has survived over 75 years (Watson, 1980). Presumably because these plants are competitive ruderals, they should be replaced over time by those plants that occupy later stages of succession. However, the time frame is unknown and apparently may be long relative to a human perspective. Alien plant persistence is further exacerbated by the lack of biotic pressure on these plant communities in North America. Furthermore, if alien plant species eventually yield to later successional species (presumably desirable native species), the time that they occupy an area may render that area less useful to useless for productive purposes (e.g., interfere with any agricultural operation, forestry, wildlife foraging, or recreational use).

Human health hazard impacts:

Virtually any pollen producing plant has the potential of affecting hay fever sufferers. In Colorado for example, ragweed (Ambrosia spp.) - native plants - cause significant problems for those with respiratory allergies. However, kochia (Kochia scoparia) and Russian thistle (Salsola iberica and S. collina) cause equivalent problems for those with hay fever. Latex in leafy spurge can cause irritation to broken skin, eyes, or simply may cause a dermal rash. Several volunteers in Boulder County, Colorado that hand-pulled diffuse and spotted knapweeds contracted a dermal rash from these weeds. This is another area where weed impacts are not well understood or documented.

Economic impacts:

The common denominator for human endeavors is our means of barter - i.e., money. Economic impacts caused by alien weeds on grazinglands has not been thoroughly documented but some information is available. Scotch thistle (Onopordum acanthium) infestations in northern California cause annual losses to ranchers equating to $60.50/acre on wet meadows, $39.50/A on wheatgrass stands, and $20.16/A on cheatgrass rangelands (Hooper et al., 1970).

The most thorough study on weed impacts on grazinglands was conducted by the Agricultural Economists at North Dakota State University. They determined the direct impacts caused by leafy spurge on North Dakota grazinglands and wildlands then used an input-output model to determine secondary effects (Leistritz et al., 1993). Direct annual losses from leafy spurge included $8.7 million in reduced personal incomes for North Dakota cattle producers and an additional $14.4 million reduction in rancher spending (i.e. lost cash outlays) due to reduced livestock production. In 1990, leafy spurge infestations reduced cattle carrying capacity by approximately 580,000 animal unit months (AUMs) or enough to support 63,100 cows for 7.5 months. Total annual direct grazingland losses were valued at $23.1 million. Indirect grazingland losses caused by leafy spurge infestations totalled $53.2 million and these losses were incurred by businesses outside of livestock production but caused by reduced income and expenditures from the cattle industry. Annual direct losses due to leafy spurge on North Dakota wildland totalled $2.9 million because of reduced wildlife associated recreation. An additional $0.7 million direct wildland loss was estimated in reduced soil and water conservation caused by leafy spurge infestations. Indirect annual losses to North Dakota wildland from leafy spurge were caused by reduced expenditures within their economy from direct losses and totalled $7.4 million. Therefore, total direct and indirect annual losses to North Dakota grazingland and wildland caused by leafy spurge were valued at $87.3 million! The majority of indirect losses in grazingland and wildland was in the household sector and totalled $28.7 million annually and equated to approximately $26.00/A infested with leafy spurge. Additionally, current infestations cause a reduction in over 1,000 jobs per year in North Dakota.

Summary and Recommendations

The negative impacts caused by noxious weeds are very real and clear where recognized. Unknown impacts exist and must be determined so we can better decide where to focus our attention. Grazingland, wildland, farmland, native habitat, open spaces, and urban landscapes all are negatively impacted by the presence of alien plant species. The domino effect from the economic impacts caused by the presence of alien plant species indicates that our daily lives indeed are negatively impacted by this 'mundane' group of plants.

We can choose to act and invoke integrated weed management strategies to reduce infestations and their impacts. Or, we can choose not to act and allow alien plants to continue to displace desirable plants thus, destroying the native biological diversity of our country and the value of our grazinglands and wildlands and further negatively impact our nation's economy. It seems very unnecessary and illogical for this latter scenario to occur!

References

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• Bucher, R.F. 1984. Montana State University Montguide 8423.

• Devine, R. 1993. The Atlantic 271,5:40-48.

• Grime, J.P. 1979. Plant Strategies and Vegetation Processes. Wiley, New York.

• Guenther, G.E. 1989. M.S. Thesis, Montana State Univ. Bozeman.

• Hakim, S.E.A. 1975. M.S. Thesis, Univ. of Montana, Missoula.

• Hooper, J.F., J.A. Young., and R.A. Evans. 1970. Weed Sci. 18:583-586.

• Kufield, R.C. 1973. J. Range Manage. 26:106-113.

• Lacey, C.A., P.K. Fay, R.G. Lym, C.G. Messersmith, B. Maxwell, and H.P. Alley. 1985. Montana State University Cooperative Extension Service Circular 309.

• Lacey, C.A., J.R. Lacey, T.K. Chicoine, P.K. Fay, and R.A. French. 1986. Montana State University Cooperative Extension Service Circular 311.

• Lacey, C.A. 1989. Fay, P.K. and J.R. Lacey, eds. Proc. 1989 Knapweed Symposium. Montana State University, Bozeman, MT. p 1- 6.

• Lacey, J.R., C.B. Marlow, and J.R. Lane. 1989. Weed Tech. 3:627-631.

• Leistritz, F.L., D.A. Bangsund, N.M. Wallace, and J.A. Leitch. 1993. Great Plains Research 3:21-37.

• Lovaas, A.C. 1958. J. Wildl. Manage. 22:275-283.

• Mack, R.N. 1981. Agro-ecosystems 7:145-165.

• Mackie, R.J. 1970. J. Wildl. Manage. Mono. No. 20. 79 pp.

• Maddox, D.M. and A. Mayfield. 1985. California Agriculture; November-December 1985:10-12.

• Miller, V.A. 1990. Roche, Jr., B.F. and C.T. Roche, eds. Range Weeds Revisited. Washington State Univ., Pullman. p 35-37.

• Morris, M.S. and J.E. Schwartz. 1957. J. Wildl. Manage. 21:189- 193.

• Rickard, W.H. and J.F. Cline. 1980. Northwest Sci. 54:216-221.

• Stevens, 1966. J. Wildl. Manage. 30:349-363.

• Thompson, D.Q., R.L. Stuckey, and E.B. Thompson. 1987. Spread, impact, and control of purple loosestrife (Lythrum salicaria) in North American Wetlands. U.S. Dept. of Interior Fish and Wildlife Service, Fish and Wildlife Research 2, Washington, D.C.

• Thompson, F., F.L. Leistritz, and J.A. Leitch. 1990. North Dakota State Univ. Agric. Econ. Rep. 257.

• Thomsen, C.D., W.A. Williams, M.R. George, W.B. McHenry, F.L. Bell, and R.S. Knight. 1989. California Agriculture; September- October 1989:4-6.

• Tyser, R.W. and C.H. Key. 1988. Northwest Sci. 62:151-160.

• Watson, A.K. 1980. The biology of Canadian weeds. 43. Acroptilon (Centaurea) repens (L.) DC. Can. J. Plant Sci. 60:993-1004.

• Weed Science Society of America. 1984. Crop losses due to weeds. Weed Science Society of America, 309 West Clark St., Champaign, IL 61820.

• Weigand, J. 1977. Montana Outdoors; January-February:6.

• West, N.E. and K.D. Farah. 1989. J. Range Manage. 42:5-10.

Roughly 5 million acres of lands that BLM manages were infested with weeds in 1985. In 1991, some 16-20 million acres were infested, a lot more in just six years. Part of that increase may be better awareness of weeds, but clearly, there has been a tremendous increase in infestation. This is a graph of the increase in the acreage covered by yellow starthistle in the period from 1958 to 1985, some of the same information presented by Dr. Beck. We go from roughly 1 million acres in the state of California to 8 million acres in the span of not quite 20 years with just one species, an incredible increase in a short time period. Clearly, we are facing worthy adversaries. How do they spread so quickly? Why are we so powerless, or seemingly powerless, to defend against their rapid spread?

What I want to do in this paper is give a brief explanation of how some of these species got to be where they are today. As Dr. Beck mentioned, most of the plants that we call weeds are not native to North America. A few species are native to a part of North America, and are not considered weeds where they originated, but have been introduced to another part of the continent where they do behave as weeds. I'll talk about how these plants got where they are in the first place, and then move on to discuss how they spread after they have been introduced and established a toehold.

With a lot of these species, what we get is not simply a plant that takes its place in the system, but one that dominates the plant community. My perspective is different than that of other presenters because many of the examples I use are from preserves, national parks, and other natural areas where I work. However, the same types of problems affect rangelands and other agricultural lands. We have a great deal in common. In central California, and in much of the country, we have ecosystems that are now so altered because of the weeds that we don't really know what they might have been like before European settlement. For example, in one of the few Southern California grasslands where there is substantial cover of the native bunch grasses, we don't have a good idea of what the community was like only 140 years ago. In ecological time, that is not very long ago, yet we're not even sure what the dominant species was then, because the non-native species have come in and so thoroughly taken over. We don't have a good idea of what the various components of the natural system were and how they related to one another. That's how complete the changes have been in this system and the same is true for other portions of the country.

How Do Weeds Get Established?

I use the modern example of the airplane as a mechanism for introduction of alien species because these new plant species are still being brought in all the time, on purpose and unintentionally. But let's move back and talk about how plants that we consider weeds have gotten here in the past. From the time of Columbus' discovery of the Americas, there has been a tremendous increase in non-native species on the two continents. California's flora is now 17.5 percent non-native. New York State's flora is 35 percent non-native. Hawaii's flora is 47 percent non-native, almost half of the plants that grow there, without any help from people (that is, they seed and reproduce on their own) are non-native plants. It's clear that there has been a tremendous transfer of plants from one place to another. How did it start? How does it continue?

The unintentional introductions were many and varied. We used to use solid ballast in our ships, usually consisting of soil placed in the hold when ships that had transported bulk commodities abroad returned to the Americas empty or only partly laden. This ballast was dumped at the landing site and often contained seeds of non-native plant species. This probably didn't happen at just one time, or just one place. San Francisco, New Orleans, Boston, ports up and down the coasts on both sides of the continent received introductions of plants in this way. Today, we don't use solid ballast as much, we use liquid ballast (water). That's probably how we got the zebra mussel and other non-native aquatic organisms.

There were also tremendous numbers of introductions in agricultural commodities themselves. We imported a lot of seed and root stock from other parts of the world. Many times, in the soil, or in the hay, or in the seed itself, there were contaminants. We imported many animals. In the coats of the animals or inside the animal waste, there were seeds of non-native plants. They may have been shoveled off in the manure and thus provided a nurturing growing medium for species on arrival in a new continent. Hundreds of species got here in these unintentional ways.

There were a lot of intentional introductions as well. As Dr. Beck indicated, many species were introduced for ornamental purposes. Many species that we consider weeds, some of the knapweeds for example, are attractive, at least singly. Spotted knapweed is a beautiful plant, with a beautiful purple flower. Purple loosestrife is quite lovely. It's planted in planters around American University here in Washington, DC, and until very recently, it was in the planters in front of the U.S. Fish and Wildlife Service building. It's a pretty plant and is going to be distributed. It was brought to the United States, on several occaisions, as an ornamental plant.

Other species were brought here for medicinal use. Foxglove was introduced, at least in parts of the country, as a medicinal plant. There are a lot of different uses for different plants. Johnsongrass was brought in as a forage plant, but later became problematic. It escaped it's master. Many of these species followed the same path. We brought them here for one purpose or another, and then they reproduced themselves. They did what was natural for them and they had few or no biotic restraints. The climate was appropriate, and they took off.

Most of the plants that we have as weeds were introduced repeatedly, often via several different pathways. They weren't generally introduced just to one spot, from there to spread to other locations. Seed stocks were brought into port cities and distributed, and then a subsequent introduction at a number of places.

Leafy spurge, which is a tremendous problem in the Northern Plains, was introduced in 1827 in Massachusetts, and it's still there. I saw lots of it in northeastern Massachusetts this spring. It was probably introduced again some time in the late 1800's, to the upper Midwest (Minnesota and the Dakotas) when people were settling from Germany and further east in Europe and in Russia. It was probably also introduced along with another species called Euphorbia waldensenia. Apparently, what we have as a troublesome species in the United States is, in fact, a hybrid of those two species. The two species didn't hybridize in Europe, but they did here and now we have a plant that is slightly different from either of its forebears and is an extremely worthy adversary. So we have all sorts of new situations here on this continent.

Some of the plants that have been transfered from other parts of the continent are plants like Spartina alterniflora, the marsh cordgrass that grows so nicely in Eastern and Gulf coast saltmarshes. It was introduced to West coast estuaries, probably as packing material around oysters that were seeded there, and now it's a tremendous problem in certain estuaries, such as Willapa Bay, Washington. Another species, black locust Robinia pseudoacacia, has been distributed as an ornamental. Thus, the same pathways of introduction that were used between other continents and the Americas have been used, to a lesser degree, to spread plants from one part of North America to another.

In Oregon and Washington, a species called Hemizonia pungens, or spikeweed, is now listed as a county noxious weed in several counties along the Columbia River. It is a native plant where I work in California, but was carried by human action over several mountain ranges to northern Oregon, probably in grain or other agricultural commodities. It's insect enemies probably do not follow it and it is doing very well; too well for agricultural interests and too well for The Nature Conservancy. It's pushing out some of the native plants we're concerned about in at least one preserve in this area.

How Weeds Spread Once Established

This is mostly common sense. Plants are introduced all around the country because we travel so much and are so mobile. I was reading an historical analysis of human civilization. The author, William McNeill's idea was that you could evaluate the advancement of civilization by the advancement of the technology for travel. It's quite clear that in the last millenium, we've increased our ability to travel greatly. About 500 years ago, we gained the ability to cross the Atlantic reliably. Once trans-Atlantic travel became commonplace, many species were introduced to this continent by ship. Now we travel all over the world and ship commodities by plane and train.

Transport is extremely rapid, even plants that have short-lived seeds can be carried thousands of miles and be dropped off on purpose or accidently with plenty of time to germinate and become established. Once a plant like purple loosestrife is in the country, it sells very well as an ornamental. It won't be kept secret. In fact, many nurseries will want to sell the plant across the country. Most of the plants that we're talking about don't need much help to spread. Most weeds, are quite well adapted to spread on their own. Think of dandelions with their thistledown seeds. They diffuse out, at least on smaller scales, quite well.

I did my dissertation work in Yosemite Valley on bull thistle (Cirsium vulgase). One of the studies I conducted involved simply following newly released seed. It was a lot of fun, but we looked pretty loony out there following seeds around. What we would do is wait for a seed to leave the seed head, and just track it down. Most dropped within 2 meters of the plant. But, over 5 percent of them went beyond my 50 meter tape, and a lot of them went completely out of sight. The thistles in Yosemite produced hundreds of thousands of seeds all together and five percent of hundreds of thousands of seeds is still a lot of seeds. When there is a burn in Yosemite National Park, usually bull thistle pops up. It can be miles from the nearest known plant, but apparently the seed has gotten there. The seeds don't usually last that long in the soil, so it's likely that those which germinate arrived just last year.

Many of the plants that we're talking about spread very well in the same types of ways. Some are spread by wind, others are spread by animals. On the preserve where I work, we have wild edible figs. They produce fruits which birds like to eat. The birds then excrete the seeds, and a new fig tree grows up in another part of the preserve. So, we're dealing with plants that are well able to spread to new areas. And, as Dr. Beck pointed out, many of these plant species are adapted for disturbed areas: areas where the soil has been turned over or where the vegetative cover has been broken in some way. Some can move into areas with extremely small disturbances (a molehill, anthill, or even a deer trail), but others can move into areas where there is no apparent disturbance.

I want to turn to the patterns of spread. An example from one of TNC's preserves is fairly typical of the type of patterns seen when weeds spread. The Pine Butte preserve in Montana covers about 18,000 acres. Leafy spurge infests roughly 1,000 acres here. The larger areas of the infestation, what we call the core areas, are probably the areas where spurge was first established on the preserve. The plant is known to have moved into the county in the 1930's, but it is still spreading quite rapidly on the preserve. We also see several smaller, outlying infestations. These have been called "nascent focii" or "outliers"; you can think of them as spot fires, like in a forest fire. These small infestations expand once established, and then coalesce to form bigger and bigger areas, which in turn throw off new outliers, repeating the process. When you get this pattern of spread, the overall front of spread is extremely rapid, at least in terms of ecological time. What we see here is a preserve that now has 1,000 acres infested and which probably had less than 400 acres infested just 10 years ago.

On a map of the Western United States, maps of the Bromus tectorum infestation at different times since 1889 have the same pattern of core areas and outliers, but on a much larger scale. At first, it infested a small area, but by the 1930's, much of the intermountain West was infested.

Model of Weed Spread

The last thing I wanted to discuss is a model of infestation. These models, developed by Rob Hengueld, depict t how diffusion of this kind may work. One way to depict spread is to draw a series of cells packed together and to assume that, from an initial establishment site in one cell, spread can occur to adjacent cells only. That's the simplest form of diffusion model. Another model using the same set of cells but allowing not only spread to adjacent areas, but also longer distance spread from one cell to another not immediately adjacent to it and with further diffusion from there. In this second scenario, a cluster of cell may fill after just 3 steps, while it would require 5 step to fill with simple diffusion alone (the first model). This second type of hierarchical diffusion results in much quicker spread and the infestation of much larger area than simple diffusion would. What we are seeing on the land with most of the weeds that we deal with, is more often the hierarchical model, due to their natural abilities and to our transport of plants from one place to another.

In the past, a great deal of concern has been voiced about nonindigenous invasive plants of agricultural lands (Rodgers, 1974; Westbrooks, 1981, 1991). This is because agriculture is a business based on profits, and such species cause major losses in farm profits. However, in recent years, this concern has been expanded to include invasive plants in natural areas (Harty, 1986, Mooney and Drake, 1986), which I call botanical invaders. A term that aptly describes both agricultural weeds and botanical invaders is biological pollution. Essentially, biological pollutants are nonindigenous invasive organisms that threaten the biodiversity of natural ecosystems or the production capacity of agricultural lands (McKnight, 1993; Westbrooks, 1991, 1992). This article will explore the issue of introduced plants that threaten grazing lands in the United States.

The World Movement of Weeds: An Explosion in Slow Motion

Since the breakup of the super continent Pangaea about 180 million years ago, there has been little chance for intermixing of taxa between the world's continents. Thus, without opportunities for genetic exchange, new species evolved on each continent, in response to local environmental pressures. Consequently, we now find quite distinct groups of plants and animals in six biogeographical realms that correspond closely to the continents (Elton, 1958; Walter, 1985).

As a hunter-gatherer, early man probably had no more effect on the distribution of plants and animals than any of the fur-bearing animals. However, with the development of agriculture, man began to move plants around both intentionally and by accident. Opportunities for movement were further enhanced with the advent of oceanic travel by sailing ships. Today, man has created artificial bridges of international commerce between distant lands that are allowing the movement of plants and animals on an unprecedented scale. This is a major ecological event, a silent explosion in slow motion, with no historical counterpart.

The main problem with introduced species is that they usually come without co-evolved predators and parasites which keep them under control (Elton, 1958). Without this pressure, introduced species often outcompete or even displace native species. In agricultural settings, they complicate pest management practices and reduce crop production. Two classic examples of this were the introduction of the rabbit (Oryctolagus cuniculus) and the common prickly pear cactus (Opuntia stricta (Haw.) Haw.) into Australia by European colonists. Both were well meaning introductions that turned out to be disastrous for the Australian countryside.

Based on an extensive review of the problem, The U.S. Office of Technology Assessment concluded that the total number of harmful nonindigenous introduced species and their cumulative impacts are creating a growing economic and environmental burden for the country. According to the report, documented losses of $97 billion were caused by 79 nonindigenous invasive species in the United States between 1909-1991 (OTA, 1993). Clearly, nonindigenous invasive plants are a real cause for concern.

Introduced Pasture and Range Weeds: A Sampler

Since the onset of European colonization, over 4,500 introduced species have established free living populations in the United States. In some cases, introduced plants are beneficial, such as soybeans (Glycine max (L.) Merr.), and wheat (Triticum spp.). However, approximately 625 introduced species (15 percent of the total) cause severe harm (OTA, 1993). Introduced weeds of grazing lands are a good case in point. Over the past 150 years, the displacement of native plants by introduced weeds has reduced the biodiversity and production capability of grazing lands in the United States. A few of the more dramatic examples are included here for illustration.

Cheatgrass and Knapweeds Invade the Intermountain West:

Prior to the mid-1800s, the grasslands of the Intermountain West (The region between the Rocky Mountains and the Cascade/Sierra Nevada Ranges) were dominated by perennial bunchgrasses such as bluebunch wheatgrass (Agropyron spicatum (Pursh) Scribner and Smith), Idaho fescue (Festuca idahoensis Elmer) and a number of broadleaf forbs. Due to the arid climate in the region, these plants evolved to germinate and grow in the spring and early summer when soil moisture from winter snowfall is plentiful. They survive hot summers in a state of dormancy and as seeds. In between the plants, lichens and other cryptogams provided a thick ground cover that retarded evaporation of moisture from the soil (Mack, 1981).

When cattle were introduced onto the Intermountain rangelands in the 1850s, they overgrazed and trampled the bunchgrasses, and broke up the cryptogam layer. This disturbance increased evaporation of soil moisture and significantly reduced the bunchgrass populations which had evolved in the absence of large hooved ungulates (Mack 1981). Subsequently, this disturbance made the rangeland very susceptible to invasion by alien plant species that grow in the fall and winter. Homesteading and cultivation of winter wheat beginning with the railroad boom of the 1880s, disturbed the land even further, and accelerated the introduction and establishment of alien invasive plants. One of the first alien weeds that began the replace the steppe vegetation of the Intermountain West was downy brome (Mack, 1984).

Downy brome (Bromus tectorum L.) is an annual or winter annual grass from the Mediterranean region that was introduced to the United States in packing materials and as a contaminant of crop seeds (Mack, 1984; Whitson et al., 1991). It occurs throughout the United States along roadsides, in waste areas, overgrazed pastures, and rangelands, and in cultivated crops. Downy brome was first collected in the Intermountain West around 1890. However, by the 1930s, county agents were referring to "cheatgrass lands", often whole counties, in which the alien had become the dominant grass (Mack, 1984). Downy brome is now estimated to infest over 41 million hectares in the western states (Mack, 1981).

Diffuse knapweed (Centaurea diffusa Lam.), Russian knapweed (Acroptilon repens (L.) DC), and yellow starthistle (Centaurea solstitialis L.), are weeds of western grazing lands that were introduced into the United States from Eurasia over the last 100 years as contaminants of crop seeds. Diffuse knapweed infests roadsides, waste areas and dry rangelands. It is a highly competitive plant that crowds out many desirable forage species. It is now estimated to infest over 1.3 million ha in 9 states and 2 Canadian provinces (Lacey and Olson, 1991; Whitson et al, 1991). Russian knapweed forms colonies in cultivated fields, orchards, pastures, and roadsides (Whitson et al., 1991). Originally, it became established in wet alkaline spots of drylands, of the Intermountain West and on the Great Plains. It is a new problem on winter wheatlands of the Palouse Prairie (Richard Old, Washington State Univ., pers. comm., Nov. 1993). It now infests over 568,000 ha in nine states and 2 Canadian provinces (Lacey and Olson, 1991). Yellow starthistle is a very invasive plant with spiny flower heads. It now grows on millions of acres of rangeland as well as roadsides and waste areas. It is now estimated to infest over 3.8 million ha in 10 states and 2 Canadian provinces (Lacey and Olson 1991). Chewing disease (loss of jaw muscle control) caused by chemical constituents in the plant, results when horses are forced to eat it. Continued feeding can result in death by thirst and/or starvation.

European Invaders at Home on the Great Plains:

Unlike the steppe vegetation of the Intermountain West that grows in the spring and early summer, the grasslands of the Great Plains were originally dominated by summer growing sod-forming grasses with underground rhizomes. Some of these taxa included big bluestem (Andropogon gerardii Vitman var. gerardii), grama grass (Bouteloua spp.), wheatgrass (Agropyron spp.), and buffalo grass (Buchloe spp.). As sod-formers, they were pre-adapted to grazing and trampling by hooved ungulates such as bison (Bison bison) and pronghorn antelope (Antilocapra americana). However, with the onset of European colonization in the 1800s, the Great Plains was invaded by perennial dicots such as leafy spurge and Canada thistle. A few examples of weeds that have become major problems on the Great Plains over the past 100 years include:

Spotted Knapweed (Centaurea maculosa Lam.) is a biennial or short-lived perennial herb with a stout taproot, up to 1 m tall. It was introduced into the Midwest from Eurasia as a contaminant of alfalfa and clover. It is now ranked as the number one weed problem on rangelands in western Montana (Whitson et al., 1991). As weeds go, spotted knapweed is very aggressive, and can infest large areas quickly. In addition, it provides very little forage for big game or livestock. It now occurs about 3 million ha in nine states and two Canadian provinces (Lacey and Olson, 1991).

Leafy Spurge (Euphorbia esula L.) is a perennial herb, up to 1 m tall that was introduced into the United States in the 1820s as a contaminant of crop seeds. It now occurs on the Great Plains, on mesic pastures of the intermountain West, and in coastal areas west of the Cascade Mountains. It now infests over 729,000 ha in Montana and North Dakota alone (Lacey and Olson, 1991). It causes severe irritation of the mouth and digestive tract in cattle which may result in death. Direct livestock production losses along with indirect economic effects to leafy spurge was about $110 million in 1990 (Bangsund and Leistritz, 1991). The extensive root system which provides large nutrient reserves make it very difficult to control (Whitson et al., 1991).

Musk Thistle (Carduus nutans L.) is a biennial or winter annual herb, which grows up to 3 m tall. It was introduced from southern Europe and western Asia in the early 1900s and is now widespread throughout the U.S. and Canada. It invades pastures, range and forest lands, roadsides, waste areas, ditch banks, stream banks and grain fields. It can also be a serious problem in alfalfa and grass hay fields (Dewey, 1991). It occurs on the Great Plains and also in mesic pastures of the Intermountain West (Whitson et al., 1991). It has been reported in 42 states and is considered a noxious weed in at least 16 states (Dewey, 1991).

Canada thistle (Cirsium arvense (L.) Scop.) is a colony forming perennial herb with deep and extensive horizontal roots, that grows up to 2 m tall. It is native to southeastern Eurasia, and was introduced into Canada as a contaminant of crop seeds in the late 18th century. Unlike other thistles, female and male flowers are produced on separate plants. Thus, a colony of male plants can maintain itself by asexual reproduction. Breaking up the roots by plowing only serves to increase the number of plants (Whitson et al., 1991). It occurs throughout most of the United States north of the 35th latitude. However, it has been declared a noxious weed in at least 33 states (Dewey, 1991).

Introduced Weeds of Eastern Pastures:

Grazing lands in much of the eastern United States were originally converted from deciduous and evergreen forests that stretched from Maine to Illinois and southward. As disturbed sites, such pastures are quite susceptible to invasion by alien taxa. However, modern agronomic practices permit the growth of introduced grass as a crop and allow it to outcompete many would be weeds. Two introduced pasture grasses that have been used successfully in the eastern United States include bahiagrass (Paspalum notatum Fluegge), and tall fescue (Festuca arundinacea Schreb.). A few examples of introduced plants that have become serious problems in improved pastures of the Eastern United States include:

Multiflora rose (Rosa multiflora Thunb.) is a thorny perennial shrub that is native to Japan, Korea, and eastern China. It was first introduced into the United States in the early 1800s for breeding roses, root stock, and as a garden plant. In the 1930s and 40s, it was promoted by the USDA, Soil Conservation Service for use as an erosion control, a wildlife food, and as a living fence. Over the years, millions of plants were given to farmers and conservation groups throughout the country (Amrine and Stasny, 1993). As a consequence, it now occurs throughout the United States to some degree (Anonymous, 1970). In West Virginia, over 14 million seedlings were planted from the 1940s to the 1960s (Dugan 1960). The weedy characteristics of the plant were first noted in the 1940s and 1950s. It is now a serious weed of marginal land such as hilly pastures, roadsides, fence rows, and right-of-ways. Multiflora rose is another example of a well intended introduction that has gone awry.

Bull thistle (Cirsium vulgare (Savi) Ten.) is a bushy, biennial plant, with spine-tipped leaves and a taproot, that grows up to 1 m tall. It is native to Europe and now occurs throughout the 48 lower states. It is listed as a noxious weed in IA, MN, PA, and WA. It occurs in meadows, pastures and along roadsides (Dewey, 1991).

Serrated Tussock. One Federal Noxious Weed that is of deep concern to American weed scientists is serrated tussock (Nassella trichotoma (Nees) Hack.), a tussock forming grass weed from South America. Currently, serrated tussock is rated as the #1 noxious weed in New South Wales, Australia, where it occurs on over 400,000 ha of pastures and causes over $11 million in losses per year to wool production (Westbrooks, 1991). Serrated tussock was introduced into the United States in 1988 as a contaminant of nine shipments of tall fescue seeds from Argentina through the ports of Jacksonville, Houston, and Portland. After documenting the contaminants, Plant Protection and Quarantine (PPQ) released the shipments to the importers due to a clause in Section 12 of the Federal Noxious Weed Act that prohibits regulation of seed shipments under the Act. By the time the law was re-examined and a stop sale order issued by PPQ in early 1989, over 25,000 kg of the contaminated seeds had been sold in 49 counties in North Carolina, South Carolina, Kentucky, Illinois, and Missouri. Surveys are being conducted in affected states to detect incipient infestations (Westbrooks and Cross, 1993).

Tropical Soda Apple. The newest threat to America's grazing lands is tropical soda apple (Solanum viarum Dunal), a newly introduced nightshade from Brazil with stout rootstocks and sharp prickles on the leaves and stems. This species was first observed in Glades County, Florida, in 1987 (Mullahey et al., 1993). It is now estimated to occur on at least 150,000 ha (370,000 acres) of improved pastures and 12,000 ha (30,000 acres) of pinelands in 26 counties of the state. Total losses due to the plant are estimated to already be over $28 million per year (J. Mullahey, Univ. Fl., pers. comm., Oct. 1993). Currently, the USDA Agricultural Research Service is conducting a study to determine the potential ecological range of the Plant in the United States. This study will reveal which areas of the U.S. are most vulnerable to invasion by the plant. It will also help determine the need for regulating the movement of livestock (which eat the fruits), hay, and sod from infested pastures and rangelands to prevent the movement of the plant to other states.

Avenues of Entry for Alien Weeds: Regulatory Exclusion by USDA-APHIS

While weed seeds may hitch hike on almost any commodity, means of conveyance, or in soil, most weed seeds are found associated with commodities that grow in their same environment. Potential vectors of pasture and rangeland weeds include crop and grass seeds, spices, miscellaneous dried plants, medicinal herbs, research specimens, raw animal hair (wool, etc.), raw animals hides, straw handicrafts, and used bagging.

In the past, one major pathway of introduction for foreign weeds was dry ship ballast in the form of rocks and soil. Today, modern ships use water as ballast and have effectively closed this avenue of entry for weeds. On the other hand, water ballast provides a pathway for movement of nuisance aquatic species into the United States. The dreaded zebra (Dreissena polymorpha Pallas) is the most recent example of this type introduction.

High risk vectors, including the commodities listed above, baggage, and other personal effects are inspected at ports of entry by PPQ Officers to ensure they are not infested with regulated weeds. Items found to be contaminated are either cleaned, fumigated, or rejected entry into the United States to eliminate potential risk. Soil contaminated equipment and vehicles are generally washed to eliminate the risk of introducing regulated weeds.

Summary

Nonindigenous invasive plants are biological pollutants that threaten the biodiversity of natural areas and crop production of agricultural lands. Alien invasive weeds including downy brome, European knapweeds, and thistles, have transformed the prairies and grasslands of the Great Plains and the Intermountain West. In the eastern United States, other aliens pose a serious threat to improved pastures. In particular, tropical soda apple, a prickly new nightshade from Brazil presents an imminent threat to Florida and perhaps other states as well.

Once native plants are replaced by primary invaders, these invaders are typically only replaced by other invaders that are even more undesirable. In the Intermountain West, downy brome has opened the rangelands for invasion by secondary invaders such as the European knapweeds and thistles. Considering the problems that now being seen with the dozen or so European knapweeds already in the United States, the prospects for dealing with the remaining 1,400 European species are frightening. The most effective answer is to keep them out (prevention (keep high risk foreign commodities from becoming contaminated), preclearance (inspection at ports of export), and exclusion (inspection at ports of import)); to detect incipient infestations (that breech our exclusion system); and to eradicate incipient infestations before they become established and spread.

The long term effects of continued homogenizing of the world's flora and fauna are unknown. However, the short term effects of alien weeds on natural and agricultural ecosystems are obvious. Unlike chemicals that start to degrade as soon as they are applied, biological pollutants have the potential to reproduce and to spread. This problem is further exacerbated by the fact that incipient infestations usually go unnoticed by the average person and often represent no more than a curiosity or "new record" to most plant scientists. For these reasons, it appears that the world movement of invasive plants and animals that become biological pollutants is one of the most underestimated threats to the sustainability of agriculture and natural ecosystems.

On a geological scale, we are recreating a global Pangaea, where invasive species will come to occupy their maximum potential ecological range. In the process, many highly desirable and functional species are likely to be displaced or eliminated all together. If left unchecked, the effects of the world movement of harmful nonindigenous species are certain to be far reaching. Therefore, the main objective of plant regulatory agencies must be to protect our natural and agricultural ecosystems from invasion by nonindigenous invasive species. This can only be done by closer scrutiny of plants and animals that are moved around the world. The lessons of the past serve to remind us of the urgent situation at hand.

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• Rodgers, E. 1974. Needed, a Federal Noxious Weed Act. Weeds Today 5:9-10.

• Walter, H. 1985. Vegetation of the earth, and ecological systems of the geo-biosphere. 3rd Edition. Springer-Verlag. NY. 318 pp.

• Westbrooks, R. 1981. Introduction of foreign noxious plants into the United States. Weeds Today 14:16-17.

• Westbrooks, R. 1991. Plant protection issues. I. A commentary on new weeds in the United States. Weed Technology 5:232-237.

• Westbrooks, R. 1992. Regulatory exclusion of Federal Noxious Weeds from the United States ofAmerica by USDA APHIS. P. 110-113 in: Proc. 1st Intl. Weed Control Cong. Intl. Weed Sci. Soc. Feb. 1992. Melbourne, VIC.

• Westbrooks, R. and G. Cross. 1993. Serrated tussock (Nassella trichotoma) in the United States. Weed Technology 7(2):525-528.

• Whitson, T., L. Burrill, S. Dewey, D. Cudney, B. Nelson, R. Lee, and R. Parker. 1991. Weeds of the West. Western Soc. Wd. Sci. and Univ. Wyoming. 630 pp.

Concerns over the introduction of alien, invasive species have escalated over the past several years and are rapidly approaching the crisis level. Exotic species dissect our national interests creating problems in agriculture, industry, natural areas and can impact human health. According to the recently released Office of Technology (OTA) Report on Harmful Non-Indigenous Species in the United States, at least 4,500 species of foreign origin have established independent populations in the United States. An estimate of documented losses from 79 exotic plant and animal species from 1906 to 1991 is placed at $97 billion. The stage is set then for an increase in the number and secondary spread of introduced exotic species whether by natural means or by human activity. One of the goals of regulatory agencies is to provide the fundamental mechanisms to detect, delimit, and control or eradicate these species before they are able to fully establish themselves and cause additional problems.

I would like to focus our discussion today of invasive exotics specifically to weeds and the potential impacts on pasture and rangeland areas. The OTA report estimates that the total direct costs of non-indigenous weeds in the United States range from $3.6 billion to $5.4 billion each year. These figures exclude the environmental, human health, regulatory, and other indirect costs of using herbicides or other means of management on exotic weed species which may exceed $1 billion yearly. Weeds, for purposes of our discussion, can be simply defined as plants growing where they are not desired. Weeds compete with our desirable crop plants for water, light, nutrients, and ultimately reduce yields. Their presence interferes with the cultivation and harvest of crops in agricultural areas. Navigational problems occur when aquatic weeds are allowed to spread into our lakes, streams, ponds, and other waterways. Introduced into a new and suitable environmental area, non-indigenous weed species are often able to grow unabated due to the lack of natural enemies. As referenced earlier, many of the documented weed pests in agricultural settings today are of foreign origin. According to the OTA report, over 2,000 plants have origins outside of the United States. Policies, then, relating to the importation of potentially damaging exotics must serve as the first line of defense in preventing future problems. To prevent the entry of harmful exotics, it has been suggested that introduced species must be examined for their ability to invade waterways, croplands, pastures, rangelands and forests. Methods of dissemination and longevity of seeds or other reproductive structures must also be reviewed. Finally, other undesirable characteristics associated with the genus or family to which the species belongs must be reviewed during the screening process.

To date, approaches addressing non-indigenous weed species in the United States have been splintered. Federal initiatives in many cases are flawed. State weed laws, while effective in preventing the intrastate movement of weeds, lack full authority for preventing interstate movement. The following initiatives represent the current federal legislative approaches regarding alien plant introductions:

• International Plant Protection Convention (IPPC) [Article 14 of the Constitution of the Food and Agriculture Organization of the United Nations]: This Act establishes an international system utilizing inspections and quarantines to prevent dissemination of pests affecting plants.

• Federal Plant Pest Act [7 USC 150aa-jj]: This Act prohibits importation or interstate transportation of plant pests which may directly or indirectly injure or cause disease or damage in any plant.

• Organic Act [17 USC 147a-e]: This Act authorizes the Secretary of Agriculture alone or with other groups to detect, eradicate, control, or retard the spread of plant pests.

• Plant Quarantine Act [7 USC 151-64a, 167]: This Act authorizes the Secretary of Agriculture to regulate imports or interstate shipments of nursery stock when necessary to prevent the introduction of plant diseases and insect pests.

• Federal Noxious Weed Act [7 USC 2801-13]: This Act authorizes the Secretary of Agriculture to regulate the entry and interstate movement of plants of foreign origin that may injure agriculture, other useful plants, navigation, fish and wildlife or public health. A 1990 amendment requires federal land managing agencies to establish and fund programs to manage undesirable plants found on property pursuant to State or Federal Law.

• Agricultural Quarantine Enforcement Act (1989): This Act prohibits shipping plants, fruit, vegetable or other matter quarantined by the Department of Agriculture.

• Forest and Rangeland Renewable Resources Research Act [16 USC 1647]: This Act authorizes the Secretary of Agriculture to conduct research and experiments designed to protect and manage forests and rangeland resources from insects, diseases, noxious plants, animals, air pollutants, and other agents.

• Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 [16 USC 4701, 4711, 4712, 4721-28, 4741, 4751; 18 USC 42]: This Act defines nonindigenous species as those outside their historic range and those nuisance species that threaten the diversity or abundance of native species.

Of the initiatives described, the Federal Noxious Weed Law should serve as the introductory step in preventing the entry and spread of exotic, invasive weed species into and within the United States. However, interpretations of the Act and a preconceived lack of authority have created significant difficulties with regulatory enforcement and action alternatives at both the state and federal levels. I would like to document problems with the Federal Noxious Weed Law and review with you proposed changes that would strengthen its enforcement. First, the definition of a noxious weed in the current Law is not adequate. The lack of a clear definition does not allow for a distinct manner in which noxious weeds are to be regulated under the Act. A proposal has been developed that would revise and expand the definition of noxious weeds to include plants such as wetland weed species and weedy pests of natural areas.

In order to provide for sound field implementation of the Law, supporting biological information and documentation of weeds as potential plant pests must be generated. The current Federal Noxious Weed Law has provisions which would allow for the establishment of a technical committee to evaluate potential candidates for designation as noxious weeds. Unfortunately, the composition and structure of this committee was poorly arranged and the group has not met since 1978. This lack of specific direction has prevented the timely listing of weed species and the development of policies and procedures for full implementation of the Law. A proposed rewrite of the Act would establish a Noxious Weed Technical Advisory Group to evaluate candidate species, develop appropriate classification criteria for noxious weeds, and to make recommendations essential to implement the Act. Presently, there is no emergency action that will prohibit the introduction of nonindigenous weed species that are not already listed as Federal noxious weeds. As a part of the rewrite, a section is proposed, that if adopted, would grant emergency authority to the APHIS Administrator to prohibit the entry of foreign weeds which meet the definition of a federal noxious weed, but have not been formally added to the list. Presently, several federal noxious weeds are being offered for sale as ornamentals in the seed and nursery trade even though Section 4 of the Act stipulates that listed federal noxious weeds cannot be moved interstate without a permit.

The interpretation up to this point within the Law has applied only to movement of species that are being moved from quarantine areas. Only one quarantine relating to the federally listed species, witchweed, has been invoked. This loose interpretation has allowed the interstate movement of all other federal noxious weeds to continue. Language has been drafted that will prohibit the intentional movement of all federal noxious weeds across state lines except under permit. Additionally, there is no classification system that would permit regulatory officials to prioritize actions taken against specific noxious weeds. A proposed amendment would outline a weed classification system that categorizes the status of federal noxious weeds. Finally, Section 12 of the Law contained a statement that the exempted the regulation of shipments of agricultural and vegetable seeds. The original intent was to avoid regulating seed shipments under two separate laws by also listing all federal noxious weeds under the Federal Seed Act. The listing under the Federal Seed Act was never accomplished. A proposed amendment would delete the statement exempting the regulation of shipments of agricultural and vegetable seeds in Section 12 of the Federal Noxious Weed Law.

As presently written, the Federal Noxious Weed Law does not adequately provide the components necessary to effectively regulate the movement of nonindigenous weed species in the United States. Examples of its shortcomings are numerous. I would like to highlight several that will be of interest to you.

Serrated Tussock (Nassella trichotoma), a federally listed noxious weed, was found as a contaminant in three shipments of tall fescue seeds imported from Argentina through the ports of Jacksonville, Florida and Houston, Texas. This weed is a clump-forming grass native to South America and has been designated as a Federal Noxious Weed. This weed is capable of reducing the productivity and carrying capacity of rangelands and pastures. In making recommendations on action alternatives, United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (USDA,APHIS,PPQ) staff initially indicated that it had no authority to hold or require treatment of the contaminated shipments due to the provision in Section 12 of the Federal Noxious Weed Law that exempts shipments of seed regulated under the Federal Seed Act. The contaminated tall fescue seed were released for distribution; however, warning statements were issued to each state outlining the potential problems with the shipments. Approximately three months later, the USDA Office of General Counsel was requested by Senator McClure of Idaho to review the decision and determine if any actions were available to prevent the sale of the contaminated tall fescue. An interpretation was handed down by the Office of General Counsel indicating that Section 6 provisions of the Federal Noxious Weed Law took precedence over the provision cited in Section 12 of the Law which referred to the Federal Seed Act.

The majority of the tall fescue seeds that had been distributed were recalled and destroyed. Unfortunately, contaminated seed were distributed in North Carolina, South Carolina, Kentucky, Illinois and Missouri in at least 50 counties. Educational efforts aimed at reminding the public about the potential devastation of this weed have been launched in most of the affected states. This example clearly illustrates the inconsistencies associated with current shipments of agricultural and vegetable seed.

Another potential rangeland weed problem is Lightning weed (Drymaria arenarioides). Lightning weed is a short-lived perennial rangeland weed that is extremely toxic to cattle, sheep, and goats. It invades rangeland areas that may be stressed from drought or improper grazing and displaces much of the desirable vegetation. It is native to north-central Mexico and has been listed as a Federal Noxious Weed. Individual states such as Arizona have launched ongoing detection programs to survey for the presence of this toxic weed since infestations exist less than 80 miles south of Arizona's border and 1\4 mile south of New Mexico's border. Support through funding and development of regulatory policies from APHIS has been nonexistent. Proposed changes in the Federal Noxious Weed Law would enhance basic state activities by providing policy direction through staff or the advisory group.

A final example illustrating potential problems with implementation of the Federal Noxious Weed Law would be the threat of Tropic Soda Apple (Solanum viarum). This is a broadleaf perennial weed reaching heights of up to 2 m. The stems, leaves, flower-stalks, and calyxes have yellowish prickles up to 12 mm long. It may be easily confused with a number of other plants in this genus. This weed can infest a rangeland area within one to two years and lower the number of animals which can be grazed because of it's unpalatability. Observed in Florida as early as 1987, it has been found as a common weed in pastures, ditch banks, citrus groves, sugar cane fields, and rangeland. Tropic Soda Apple infestations of pastures in south Florida have been estimated to be nearly 61,000 ha. Presently, it is not known to occur at any other location in the United States. Given its potential economic impact in agricultural fields, rangelands, and natural areas, this weed deserves listing on an emergency basis to prevent spread to additional areas. The emergency listing would provide needed time to devote to basic plant biology and range studies to examine its potential threat to other areas in the United States. The proposed rewrite of the Federal Noxious Weed Law would provide for emergency listing.

The incorporation of these necessary changes within the Federal Noxious Weed Law originated several years ago within the Federal Noxious Weed Law Committee of the Weed Science Society of America (WSSA). These proposed amendments were carried by representatives of WSSA to Washington on their visit with members of Congress. The Intermountain Noxious Weed Advisory Council (INWAC) has also been a major player and both groups have worked cooperatively on a rewrite of the Federal Noxious Weed Law. INWAC is a grassroots action oriented organization that serves as a liaison between states, Congress, federal agencies, and trade organizations on issues regarding undesirable plants. The rewritten Federal Noxious Weed Law was circulated among members of several groups for comment and discussion including WSSA, INWAC, Nature Conservancy, Natural Resources Defense Council (NRDC), and National Coalition Against the Misuse of Pesticides (NCAMP). Representatives within state agencies throughout the country have also reviewed the rewrite.

Presently, the rewritten version of the Federal Noxious Weed Law is waiting to be introduced into Congress. It is scheduled to be introduced by Senator Bryan Dorgan, North Dakota tentatively as part of updates to the 1990 Farm Bill. It will likely be introduced in the House of Representatives by Charlie Rose of North Carolina. The hope is with these additions and an adequate funding base, federal agencies will have the proper and necessary framework to prevent the entry and spread of non-indigenous weed species.

References

• Campbell, Faith Thompson. 1993. Legal Avenues for Controlling Exotics. Pgs. 243-250 in Biological Pollution: The Control and Impact of Invasive Exotic Species., B. N. McKnight (ed.), Indiana Acad. Sci., Indianapolis.

• Mullahey, J. J., Nee, M., Wunderlin, R. P., and Delaney, K. R. 1993. Tropic Soda Apple (Solanum viarum): A new weed threat in subtropical regions. Weed Technology 7(3): 783-786.

• U. S. Congress, Office of Technology Assessment, Harmful Non-Indigenous Species in the United States, OTA-F-565 (Washington, DC: U. S. Government Printing Office, September, 1993).

• Williams, M. 1980. Purposefully introduced plants that have become noxious or poisonous weeds. Weed Science 28: 300-305.

Q: Is there any time frame for introduction of legislation to amend the Federal Noxious Weed Act?

A: George Hittle: We're just waiting for Senator Dorgan to identify an opportune moment to drop the bill in. We might wake up one morning to a call saying, hey, we introduced the bill today.

A: Howard Singletary: What we're doing is sitting on the launching platform, we have the necessary contacts and linkages and the opportunity I outlined is the major opportunity that's being considered right now.

Q: Could you comment on the changing role for Federal agencies?

A: Howard Singletary: Let me see if I can do that in the context of what this Forum is about, rangelands. Let's talk about Midwest and West first, and then I'll move to the East Coast. I think the impetus for a lot of additional cooperation at the Federal and State level is the 1990 Farm Bill amendment that I mentioned that added Section 15 to the Federal Noxious Weed law. It provided the impetus for communication forums between Federal land managers and State agencies. There has been considerable progress made in that area. One of the principal deterrents at this point in time is a lack of funding. You've seen how some of these exotic rangeland invaders can spread, in terms of the number of acres. There is no one single strategy that will effectively deal with all these plants; it will take integrated approaches that are now being worked out. One of the things that we hope to see more fully utilized is the application of biological controls where they are feasible and where there are adequate natural enemies that can be used against some of these introduced species.

Now, let's move east and let's talk about the evolution of Federal policy. I think there was a hearing held in Washington several years ago where the Administrator of APHIS was called forward to lay out the agency position as regards noxious weeds. Essentially Congress called the Administrator of APHIS on the carpet. That was the impetus for the agency to reexamine their approach and policy on noxious weeds. APHIS does have a rewritten policy that is presently in the Undersecretary's office under review. I think it will ultimately be released and I think it will be in concert with the approaches we have outlined in terms of where we need to go to deal with alien invaders and noxious weeds. That, plus the OTA study all coming together may be enough of a critical mass to move more appropriately in terms of the legislative authority as a first line of defense in preventing future introductions, to the extent that you can utilizing an approach like this. I hope it will also provide a better domestic program in terms of programs through out the country to deal with weeds.

A: Randy Westbrooks: In reference to the OTA report, the best thing is that there was nothing new in it. It might be new to you, but to us in APHIS, we've known these things for a long time. It was nice to have someone else do an independent evaluation and say "Yes, these are the problems, this is what we need to be doing". It almost gives us a blueprint of activities that we can pursue. Faith worked with us on this policy project over the last several years and we're all really happy with how it turned out. After it gets approved, I think you will all be happy about it, too. We're just beginning a plan for actually implementing this policy. We really are addressing the concerns that were addressed in the OTA report.

The two points I wanted to make, but ran out of time are these: There are about 12 or so European knapweeds in the U.S. that are infesting millions of acres and causing millions of dollars of damages. Remember this, however, there are 1,400 species left in Europe that have never come here. What's going to happen if 10 more or 20 more are allowed to be introduced? You folks are the ones concerned about grazing lands: What will they look like in 15 years if we don't do something now? APHIS can't take the blame for letting these knapweeds into the U.S. because we weren't around when they were first introduced. But now we have to really take a serious look at these things because there's a lot more to come in.

The last comment is that about 5 years ago I did a study of Australian plants. I know of 100 poisonous rangeland plants in Australia that don't occur here. So, youv'e got 100 in Australia that are poisonous to cattle and 1,400 European knapweeds, so there's an awful lot out there that could cause us future problems.

The National Agricultural Chemicals Association is the trade group that represents the common interests of the manufacturers and formulators of crop protection chemicals in the United States. We are the folks whom, it seems, many in the media and public interest groups love to hate. My responsibilities in regulatory affairs keeps me in frequent contact with the Environmental Protection Agency, interpreting and implementing laws through regulation that Congress, in its finite wisdom, sees fit to inflict upon us.

My professional training from the age of 16 on has been in Weed Science, so the theme of this year's Grazing Lands Forum is of particular interest to me. I have come face to face or should I say hand to spiny leaf with many of the noxious critters we have been discussing today. Given the long struggle to put in place and enforce an effective Federal Noxious Weed Act, weed scientists have often felt neglected and forgotten. It is a long-standing lament among weed scientists that Integrated Pest Management, a renewed battle cry in the Clinton Administration's pesticide reform proposals, means "give more money to your friendly entomologist."

To set the stage for my perspectives on noxious weeds on grazing lands, I'd like to share with you a couple of anecdotes.

In Cache Valley, Utah where I grew up, I remember numerous pastures within or near the city limits where forlorn four-legged creatures grazed among but ignored what appeared to be very lush forage. On my first real summer job as a teenager assisting in weed science research at Utah State University, I learned that the lush forage the horses wouldn't touch is a plant called goats rue, aptly named because not even goats will eat it. It is also known locally as professor weed, named for the hapless academic who decades ago introduced it from a foreign source. He thought it had potential as a forage crop, only to discover to his dismay that it is unpalatable and toxic to livestock, fairly vigorous though not an aggressive spreader, and a prolific seed producer. In recent years coordinated efforts to eradicate this weed have been quite successful.

In 1989 I took my family to visit Yellowstone National Park on a vacation trip. One evening we stayed at Mammoth Hot Springs near the norther border of the park. The next morning as I wandered leisurely along the nearby trails I noticed an unfamiliar pretty yellow flowering plant, Although I grew up in the west and had taken botany and plant taxonomy courses and had wandered the hills to study plants, I didn't recognize it. It turned out to be quite common in that area of Yellowstone Park, growing along many of the road sides. A short while later I noticed a crew of workmen dressed in rather elaborate protective clothing, including what looked like yellow rubberized coveralls, gloves and hats, pulling up these same plants--not spraying or cutting or mowing them, just pulling them up with their gloved hands. I learned that the rather attractive target of their eradication efforts was Dalmatian toadflax, a pernicious weed creeping into the park from areas further north. The incongruous image has stuck in my mind of elaborate high tech preparations to combat a lowly but very successful enemy using primitive means, totally ignoring the enemy's ability to escape such tactics and outwit its attackers.

These are just a few examples of weeds that can strike fear in the hearts of knowledgeable farmers and rancher who must use, manage, and depend on grazing lands for a livelihood. Other such weeds, ranging from the well-known to rather obscure, include leafy spurge, Russia knapweed, Astragalus, Texan blueweed, musk thistle, and whitetop. They are noxious, pernicious, aggressive invaders of grazing lands that injure and poison livestock, reduce productivity and land values, crowd out desirable forage species and endangered plants, and defy attempts to control them. Common among them are vigorously creeping perennials and allelopathic plants that produce there own natural herbicides to discourage competing plants.

As a representative of the crop protection industry I wish I could say your weed worries are over, that we have a new batch of herbicides coming on the market that, used individually or in mixtures, will handle any combination of weed problems you will find in range or pasture. But that is not the case. First of all, our wits and ingenuity and good fortune in research do not yet match nature's diversity, complexity, and resourcefulness. Second, we as a society sometimes are our own worst enemy by importing new weedy plants from other areas, usually unknowingly, but sometimes knowingly though unwittingly. One wonders if it might sometimes be intentional. You will recall in the biblical parable the master's response to the servant's report of tares sown among the wheat: "An enemy hath done this."

And third, in spite of the large land area represented by grazing lands in the United States, far more than any other single crop, forage weed control is by no means a major target of commercial research for new product development. The economics of grazing land management are such that expenses for weed control assume a relatively low priority. It seems ridiculous to consider the forage grown on hundreds of millions of acres as a "minor crop," but for purposes of pesticide product development, that is indeed the case.

In the successful fight against noxious weeds, whether one species or many, there must be three facets:

Regional planning and coordination--The serious noxious weed problems that afflict grazing lands are typically very widespread or threaten large areas. The plants are aggressive competitors, spreading vigorously by prolific seed production and efficient natural seed dispersal, and/or vigorous creeping roots or rhizomes. Localized efforts, no matter how successful the strategy, cannot expect to prevail if the species can simply move back in a year or two later. It must of necessity be a long-term coordinated plan, or success will spotty and ephemeral.

Cooperative efforts of landowners and land-controlling state and federal government agencies--If any one landowner or land controlling state or federal agency refuses or neglects to perform his duty in a well planned regional strategy against a particularly aggressive weed, his land serves as a reservoir of seed and other propagules for the surrounding area, hampering and frustrating the efforts of others. Whether it is opposition to the use of herbicides, failure to budget the necessary resources, or other reasons, all can suffer because of the actions or inactions of one party.

Integrated weed management - using all available tools, techniques, and strategies--Above all, proper management of desirable forage species is most important. Their competitiveness against weed species must be encouraged and enhanced by maintaining soil fertility levels and properly controlling grazing. Without such practices, any other strategies for directly attacking the weeds themselves can only have limited success, at best.

In many, but unfortunately not all circumstances, herbicides make a significant, effective, and economical contribution to controlling serious rangeland weed problems. They must of course be used with due consideration for the risks involved of residues transmitted to feed and food, and potential harm to nontarget species. For the most part, fears of these problems are vastly overrated. The mere presence of insignificant quantities of a man-made compound in a natural area is not necessarily evidence ecological disaster or even any hazard at all. It may be a small and utterly meaningless price to pay for the tremendous benefit to mankind.

It would be shortsighted to avoid effective chemical use for weed control in rangelands because of misguided concerns about pollution, when weeds themselves are a severe form of self-perpetuating biological pollution that does not degrade and disappear if you leave it alone.

Development of resistance of weed populations to herbicides is a growing but not unmanageable problem. Herbicide resistance is not a permanent genetic change in a weed population. In absence of the selection pressure created by continued use of a particular herbicide active ingredient, those resistant plants are generally less fit ecologically than non-resistant plants, and will be crowded out due to competition. Rotation of effective herbicide tools is an important and viable IPM technique. This means we need more, not fewer, choices of herbicides for weed control.

In a few situations we have been spectacularly successful in controlling rangeland weeds with classical biological control strategies--St Johnswort in the United States with a natural insect enemy and prickly pear cactus in Australia with plant disease are well known examples. However, the research process is long and expensive and even more dependent on good luck than is the search for a commercially successful new herbicide. Biological control for all its hype and promise, is still a distant dream for most weed problems. Research efforts in this area can and must continue, and the promise of biotechnology hints excitingly at possible commercially exploitable biological strategies. In the long run, the biological approach to weed control must prove itself in the marketplace, both in efficacy and economics. Over-reliance on the yet unfulfilled promise of biological control and so-called "biological" products from a public policy perspective, while the use of herbicides is curtailed on high moral grounds, will lead to bitter disappointment and potential disaster while we wait for the miracles to happen.

I'd like to share with you some insights into the status of various laws and regulations that have an impact on grazing lands, some dealing with weed control and some which don't. I'm indebted to Dr. John Thorne of the NACA staff for sharing his thoughts on these topics with me.

• For 20 years, it tightened controls on "Point Sources" of municipal and industrial pollution with permits, fees, fines and mandatory controls on amounts discharged.

• The goal was to restore and maintain the purity and biological habitat of our water, and eventually totally eliminate "toxic" discharges. Back then, "toxic" was mercury, cadmium, dioxin, etc.

• EPA and state efforts reduced pollutant loadings by about 90 percent. Most of agriculture was exempted.

• Today, however,"toxic" has been expanded to include nutrient and pesticide traces in runoff rainwater, eroded soil sediment from construction and farm sites, and habitat destruction.

• Both the Senate and the House of Representatives are working on bills to reauthorize and amend the Clean Water Act to add tough new non-point source pollution controls and antidegradation rules for public and federal watersheds and private lands adjacent to them.

• From a practical standpoint, this could eventually treat agriculture and livestock production the same as the previous law treated steel mills. Every fertilizer and pesticide user would be affected.

• Although agriculture and livestock producers have long been leaders in the responsible use of fertilizers and pesticides, we will be seriously challenged to do better.

• This 20-year old law will be reauthorized and amended next year, and we can expect indirect attacks on pesticide and fertilizer use.

• Urban and suburban water suppliers must now monitor for contamination from 83 pollutants (25 pesticides) and notify the public when they find it.

• Water bills now warn of the presence of pesticides, etc., and the potential health hazards of drinking the "contaminated water".

• Water suppliers must also filter or otherwise remove the contamination. Filtering is very expense and they will pass the costs onto customers across the nation.

• Water supplier associations are lobbying for Congress to come down hard on "non-point sources" during this reauthorization cycle.

• The Administration is seeking additional regulatory clout for the EPA and significant restrictions of land uses around current and potential water supplies. This could impact agriculture and livestock production in these areas.

• Presently under the Federal Insecticde, Fungicide, and Rodenticide Act (FIFRA), EPA may restrict, cancel or temporarily suspend pesticide uses that pose unreasonable risks to the environment (water quality, aquatic life and wildlife) or human health. Benefits of the pesticide use are brought into consideration in making this decision.

• EPA currently requires each state to design and implement an approved groundwater protection plan to protect from pesticide contamination. These may include severe local restrictions or bans on the use of those pesticides shown by groundwater testing to be problem contaminants.

• As part of the current FIFRA reauthorization process, the Clinton Administration has presented to Congress recommendations for changes in the law, several of which could directly affect agriculture and livestock production:

  1. Registration Sunset: All pesticide registrations must be renewed every 15 years. This will add to the minor use problem we now face.

  2. Pesticide Phase Out/ Phase Down: A new restriction process to kick in if EPA concludes that a pesticide is "reasonably likely to pose a significant risk to the environment or humans". We could quickly lose valuable tools.

  3. Reduction of Pesticide Risks and Pesticide Use: An effort by EPA to reduce pesticide risks by reducing use. Also promotion of integrated pest management (IPM). IPM training could be included in required certification training programs.

  4. Increased Pesticide Use Record Keeping: Require recordkeeping for all pesticide uses, not just restricted use products.

  5. Stronger Enforcement Authorities: More inspections, recordkeeping audits, addition of "whistle blower" and citizen suit provisions, and significant increases in penalties for improper use.

• This law is designed to protect the habitat and encourage reproductive success of threatened or endangered species listed by The Fish and Wildlife Service. Presently 755 species are listed. There are 400 candidates for listing and another 3,400 are being considered for listing.

• It expressly prohibits "taking" a listed species, meaning to "harass, harm, hunt, shoot, wound, kill, capture the species or modify/degrade their habitat in such a way as to alter their behavior or impair their lives.

  The Endangered Species Act requires federal agencies to ensure that any activities they regulate adequately protect endangered species. In fulfillment of its obligation, EPA began implementing such a plan with respect to pesticides in 1987, but complaints about failings and shortcomings of the plan were so vigorous that the Agency had to go back to the drawing board. A revised proposed plan was published for comment in 1989, and we are still waiting for the final version.

• The current plan, as it is developing, would prohibit use of certain pesticides where the growing list of species and subspecies lives. It does not provide compensation to landowners when livestock production, timber harvesting, or farming practices would be blocked.

• Habitat bulletins are being prepared by EPA and FWS for each county where vulnerable species are found. The bulletins should include a habitat map and description, and pesticide use limitations. These will be available from a variety of sources.

• Pesticide manufacturers are to add generic statements to product labels that direct users to comply with the use limitations outlined in county bulletins.

• 1994 is EPA's target date to reveal the final rule. The first year would be voluntary compliance, with enforcement to begin in the next full year.

• As the list of endangered species grows and efforts to protect habitat (i.e., clean water for aquatic species, riparian areas and wetlands for breeding, etc.), the impact of the law and regulations on pesticide use will most likely increase.

One estimate places 90 percent of the identified endangered species in the Western U.S., with 75 percent of them being plants. A high proportion of those will occur on the grazing lands of concern to you folks. This has serious potential repercussions for controlling weeds with effective herbicide treatments on grazing lands. While herbicide use may even enhance the habitat for endangered plant species (more on this in a moment), the mechanics of the regulations can very easily impede or prohibit approval of herbicide use in areas where endangered may occur. One comes to the inescapable conclusion that any herbicide "may affect" an endangered plant species, just because it is a plant. We can't test the herbicide directly on that plant, simply because it is endangered, and the fact of herbicide selectivity make inferences from other species questionable or meaningless. Furthermore, EPA and FWS lack adequate mapping data for habitats of the various endangered plant species, are reluctant to disclose what data they do have for fear collectors will destroy the plants, and lack the resources the develop the data. These combined concerns have been reason enough to place the Endangered Species Protection Plan on hold in the Office of Pesticide Programs.

Last August I attended a regional workshop at Utah State University that addressed the problems and challenges of implementing an endangered species protection plan for pesticide use. One of the most interesting recommendations to come out of the discussions at that workshop was that no restrictions should be placed on pesticide use if habitats or locations cannot be revealed because of concern that such action would further endanger the species. In other words, if the hazards to the endangered species of publicly revealing its location are greater than the hazards of pesticide use to that same species (which I suspect will occur in the vast majority of cases), no restrictions should be placed on pesticide use.

One last anecdote reveals a potential folly in categorically avoiding the use of herbicides to solve weed problems of a magnitude analogous to those found on grazing lands, supposedly for reasons of ecological ethics. Rick Johnstone runs the rights-of-way vegetation management program for Delmarva Power Company here in the mid-Atlantic states. He has developed a very successful system of judicious herbicide use to maintain vegetation along power lines in various stages of ecological succession. Obviously, fully developed forests are not compatible with maintaining utility rights-of-way, but bare ground is not desirable either. Mechanical means of destroying unwanted vegetation over the large areas involved are highly disruptive of wildlife habitat and encourage devastating soil erosion problems. The use of herbicides solves these specific problems. It has also produced some unexpected but most welcome ecological benefits. A few endangered plants species have recently been discovered thriving along these rights of way which were thought to have long since disappeared from the area. The opening up of the forest canopy to maintain habitats of intermediate ecological succession has reduced plant competition so that these delicate species can return and survive. It would not be economically or physically feasible without herbicides.

Noxious weeds infest millions of hectares for grazing land in North America. These weeds reduce the amount of available grazing land and reduce the palatability and quality of the forage available to grazing livestock. Thorny weeds, such as thistles, briars (Rubus species), multiflora rose (Rosa multiflora), spiny amaranth (Amaranthus spinosus), and horsenettle (Solanum carolinese) can form dense, unpalatable patches rendering large areas of fields useless for grazing. Most weeds have less nutritional value than the forage on grazing lands, but even if the weed is nutritious, toxic substances may be present. If consumed in large enough quantities, many weeds are poisonous, creating sickness and death. Fortunately, most animals avoid grazing near poisonous weeds unless forage is limited. Thus, the incidence of livestock poisoning from poisonous weeds is unusual, but light infestations of weeds can render large