Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Biological Sciences

Department

Biological Sciences

First Advisor

Steven R. Alm

Abstract

The “annual bluegrass weevil” (Listronotus maculicollis) became resistant to synthetic pyrethroid insecticides (bifenthrin and cyhalothrin) in several adult weevil populations from Connecticut, Rhode Island, and Massachusetts in 2007-09, and management of this insect has become increasingly complex. Annual bluegrass weevil continues to be a serious pest of Poa annua L. (Poaceae) and bentgrasses (Agrostis spp) on many golf courses in mid-Atlantic and northeastern United States and eastern Canada. Adults chew notches on grass blades and at the juncture of leaves and stems. However, adult feeding has little effect on plant vitality. Early instars feed inside plant stems and late instars on plant crowns. The first generation larvae, which usually become apparent in late May or early June, typically cause the most severe damage. During July and August damage caused by second generation larvae is usually less extensive, especially if good control of the overwintering generation was obtained. In most cases, adequate control of the insect has been achieved through the use of pyrethroid applications targeting adult weevils as they emerge from overwintering sites and before they begin to lay eggs. However, if a population is resistant to pyrethroids, alternative controls are required to prevent damage. My research objectives were to evaluate the entomopathogenic fungus Beauveria bassiana for control of L. maculicollis and how neonicotinoid insecticides can best be used to manage this increasingly serious pest.

While pyrethroids remain the preferred choice of many golf course superintendents for managing this species, resistance has forced some superintendents to incorporate other strategies. Some of the new strategies include: (1) the use of a pyrethroid or chlorpyrifos early against overwintering adults; (2) neonicotinoid/pyrethroid combinations (Aloft, Allectus) during peak adult emergence to control adults and first generation larvae; (3) primarily preventative larvicidal compounds (chlorantraniliprole (Acelepryn), neonicotinoids) for early instars; and (4) curative larvicidal compounds (trichlorfon (Dylox), spinosad (Conserve), indoxacarb (Provaunt), chlorpyrifos, pyrethroids) for control of fourth and fifth instars. Some locations may need to use one or more of these strategies to prevent turf damage and resistance development. It is imperative that the timing of treatments coincide with various life stages (adults, early or late instar larvae) to maximize chemical efficacy. This is particularly important for the systemic compounds (neonicotinoids/chlorantraniliprole) to insure there is sufficient chemical in the xylem for maximum effectiveness. If treatment strategies 1-3 are not effective, a curative larvicidal compound may need to be applied to prevent damage. Finally, since all subsequent generations come from the overwintering adults, it is imperative that a superintendent control those adults and any larvae that they produce (1st generation).

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