Tall Fescue Online Monograph

Several insects, in addition to fall armyworm discussed earlier, injure tall fescue turfs (Table 26-6).

Most species of white grubs, the larvae of scarab beetles, including the Asiatic garden beetle [Maladera castanea (Arrow)], European chafer, [Rhizotragus majalis (Razoumowsky)], green June beetle [Cotinis nitida (L.)], Japanese beetle, and northern [Cyclocephala borealis (Arrow)], and southern masked chafers have one generation each year (Fig. 26-15). Black turfgrass ataenius [Ataenius spretulus (Halderman)] may produce several generations annually. Depending on latitude, the oriental beetle [Anomala orientalis (Waterhouse)] may require 2 yr to complete one generation (Vittum et al., 1999). May or June beetles (Phyllophaga spp.) may take 1 to 4 yr to complete one generation. Major turf damage from May or June beetle grubs in the northern United States often results from feeding activity during the second year of both the 2- and 3-yr cycles as larvae become third instars (Tashiro, 1987b). Generally, grubs feed on plant roots. Curled white grubs with hard, capsule-like heads often are visible in soils as heavily infested turfs are rolled back like carpet. Although they usually feed on decaying organic matter rather than live plant tissue, green June beetle larvae injure turf by loosening soil around plants and exposing roots (Bambara, 2003).

Sod webworms (Crambus spp. and others) are small tan or gray moths in the family Pyralidae, subfamily Crambinae. Larvae of more than 20 species of sod webworm are capable of injuring turf (Koppenhoffer, 2001). Female moths of several genera including Agriphilia, Crysoteuchia, Crambus, Fissicrambus, Microcrambus, Parapediasia, Pediasia, Surattha, Tehama, and Urola deposit eggs as they fly over turf in the early evening (Vittum et al., 1999). Newly hatched webworm larvae begin feeding immediately on leaves. Sod webworms overwinter as larvae in silken tunnels or webs close to the soil surface (Hale, 2006). Some species including the subterranean webworm [Chrysoteuchia topiaria (Zeller)] feed on roots (Heller, 2001).

Cutworms (Noctuidae spp.) and armyworms belong to a group of night-flying moths in the family Noctuidae. Black, bronzed [Nephelodes minians (Guenée)] and variegated [Peridroma saucia (Hübner)] cutworms are caterpillars that feed on leaves and stems of young plants, cutting them off at the soil surface. Each female cutworm moth can lay as many as 500 eggs. Eggs often hatch in 5 d or less and larvae develop fully in about 4 wk (Bambara and Brandenburg, 2003). Armyworms are closely related to cutworms and cause similar damage. Armyworm [Pseudaletia unipuncta (Haworth)], fall armyworm, and lawn armyworm [Spodoptera mauritia (Boisduval)] attack turfgrasses. Larvae of brownish-gray, armyworm moths can destroy the aerial shoots of young turfgrasses quickly. They are about 3.8 cm (1.5 in) long, green, and have dark stripes along each side of the body and down the center of the back (Hodgson, 2007). Armyworms tend to feed on tall fescue turf in groups, while cutworms are solitary feeders.

To be effective, most insecticides must contact the target insect pest directly. Some, for example, acephate [(RS)-(O,S-dimethyl acetylphosphoramidothioate); Orthene Turf, Tree & Ornamental Spray, AMVAC, Newport Beach, CA] and trichlorfon [dimethyl (RS)-2,2,2-trichloro-1-hydroxyethylphosphonate; Dylox, Bayer), act quickly, within 1 to 4 d after treatment, and provide control for about 1 to 2 wk. Chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate; Dursban Pro, Dow) usually takes effect within 3 to 7 d following application and remains active for 2 to 5 wk. The insecticides fipronil [5-amino-1-(2,6-dichloro-a,a,a-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile; Chipco Topchoice, Bayer] and imidicloprid [(E)-1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine; Merit, Bayer] may require 10 or more d to have a noticeable effect on the target insect pest, and remain active for more than 1 mo. The insect growth regulators fenoxycarb [ethyl 2-(4-phenoxyphenoxy)ethylcarbamate; Award, Syngenta], halofenozide (Mach 2), and hydramethylnon {Tetrahydro-5,5-dimethyl-2(1H)-pyrimidinone(3-[4-(trifluoromethyl)phenyl]-1-(2-[4-(trifluoromethyl)phenyl]-ethenyl-2-propenylidene) hydrazone; Amdro, BASF} prevent insects from maturing.

Several biocontrol agents also control turfgrass insects. Some species of nematodes penetrate the bodies of insects and release bacteria that cause disease. For example, cultivars kurstaki and japonensis (buibui strain) of the Bacillus thurgiensis (BT) bacterium, are toxic to some species of cutworms and webworms, and to annual white grubs. Bacillus popilliae (BP) is a naturally occurring soil bacterium, also available commercially, that causes milky spore disease.