A complex of four billbug species (Sphenophorus spp., Table 9-1, Fig. 9-8) native to North America can infest cool-season turfgrasses in the United States (Johnson-Cicalese and Funk, 1990; Johnson-Cicalese et al., 1990). In spring overwintering adults become active, feeding and ovipositing in grass stems. Billbugs generally have a single generation per year, but in some locations and some years a partial second generation may occur. Billbug larvae burrow through grass stems, killing individual tillers. The damage they cause may go unrecognized or be attributed to drought or other insect pests (Shetlar, 1995). While damage appears to be more severe on Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass free of N. lolii [(Latch, M.J. Christensen & Samuels) Glenn, Bacon & Hanlin], under laboratory conditions E- tall fescue also is a suitable host (Johnson-Cicalese and Funk, 1990). Murphy et al. (1993) estimated that feeding damage by billbugs, mainly S. venatus vestitis and S. minimus, resulted in a 25% loss of turf cover in E- tall fescue in New Jersey.


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Argentine stem weevil (Listronotus bonariensis) (Fig. 9-9), a pest very similar to the billbug, is found infesting grasses in South America, Australia, and New Zealand. Tiller mining by the larvae causes severe damage to perennial ryegrass in New Zealand. Like the billbug, tall fescue appears to be a less favorable host than ryegrass for Argentine stem weevil (Goldson, 1982; Barker, 1989), but occasionally can be damaged severely by this pest (Prestidge et al., 1986, 1989). Newly established swards are particularly vulnerable during the spring-summer period after a fall planting; use of an insecticide at this time can result in a substantial increase in yield (Barker et al., 1984).




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Fig. 9-8. Billbug, Sphenophorus spp. adult (left, photo: Fred Baxendale) and larva (right, photo: Doug Richmond).


Fig. 9-9. Argentine stem weevil, Listronotus bonariensis (photos: AgResearch).



Effect of Endophyte

Adult billbugs of the four species listed in Table 9-1 do not appear to be deterred by endophyte in tall fescue, but their survival is reduced (Johnson-Cicalese and White, 1990). In the field, lower billbug populations and considerably less damage have been recorded on E+ tall fescue in two trials in New Jersey (Murphy et al., 1993).

Sensitivity of Argentine stem weevil to N. lolii infection of ryegrass is well documented (Popay and Rowan, 1994, and references therein). Primarily the resistance is mediated through the effects of the alkaloid peramine, which is a powerful deterrent to the adult. This reduces not only feeding but also oviposition and thus decreases larval damage, although other alkaloids produced by the endophyte also can act directly on the larvae. Tall fescue infected with endophyte also deters adult Argentine stem weevil feeding (Barker et al., 1983; Popay et al., 2005) even though peramine concentrations are considerably lower in tall fescue than they are in N. lolii infected perennial ryegrass. The role of loline alkaloids in the resistance of E+ tall fescue to billbugs and Argentine stem weevil has not been investigated.



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