Date of Award

2009

Degree Type

Dissertation

First Advisor

Steven R. Alm

Abstract

The annual bluegrass weevil, Listronotus maculicollis Kirby (Coleoptera: Curculionidae), has emerged as a serious pest of Poa annua L. (Poales: Poaceae) (annual bluegrass), in the Northeastern US. In 2007, topical application bioassays of bifenthrin and λ-cyhalothrin conducted on field-collected populations of L. maculicollis Kirby from eight southern New England golf courses resulted in LD50 ranges of 1.80-244.67 ng/insect and 0.52-159.53 ng/insect for bifenthrin and λ-cyhalothrin respectively. These results revealed low to high levels of resistance to bifenthrin (6.1-135.9 fold) and λ-cyhalothrin (28.7-306.8 fold), possibly due to insecticide overuse. In 2008, topical application bioassays with bifenthrin and bifenthrin plus synergists affecting three detoxification systems were conducted on four field-collected adult populations of L. maculicollis to determine if resistance was metabolically mediated. In the population with the lowest resistance only detoxification by cytochrome P450 monooxgenases (P450s) was significant. Detoxification in the population with the second highest level of resistance involved both P450s and glutathione S-transferases (GSTs), and detoxification in the population with the highest level of resistance involved P450s, GSTs and carboxyl-esterases (COEs). Since P450s are inhibited by demethylation inhibitor fungicides (DMI-Fs) and gibberellin inhibitor plant growth regulators (GI-PGRs), both of which are commonly used on golf courses, we tested these compounds using topical application bioassays and simulated field trials for synergistic activity with bifenthin against a pyrethroid resistant population of L. maculicollis . The LD50 for bifenthrin (120 ng/insect) was significantly higher than the LD50s for bifenthrin plus the fungicides fenarimol, fenpropimorph, prochloraz, propiconazole, pyrifenox and plus the plant growth regulators, flurprimidol, paclobutrazol and trinexapac-ethyl (range of 8-36 ng/insect). The means of mortality for Talstar® (bifenthrin) in combination with each of the following, BannerMAXX® (propiconizole), Rubigan® (fenarimol), Cutless® (flurprimidol) and PrimoMAXX® (trinexapac-ethyl) ranged from 9.8 to 14 and were significantly higher than an untreated control (0.3) and Talstar ® (5.0) alone. We also studied the effects of liquid and granular formulations of Metarhizium anisopliae (Metschnikoff) Sorokin strain F52 against L. maculicollis larvae under field conditions. The liquid formulation provided 31-46% control of L. maculicollis larvae, but the granular formulation provided no control.

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