Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Steven R. Alm

Abstract

Bioassays were designed to evaluate Beauveria bassiana (Balsamo) Vuillemin strain GHA against Listronotus maculicollis (Kirby) adults. B. bassiana and its “inert” carrier oil in the product BotaniGard and the “inert” carrier oil alone provided 99 and 96% mortality respectively in Petri dish assays 1 d after treatment when applied in 1 ml water. When the same treatments were applied in 0.5 ml of carrier water mortality was only 1.4 and 0.7% respectively 1 d after treatment. After 10 d in Petri dishes, B. bassiana and its “inert” carrier oil and the “inert” carrier oil alone applied in 0.5 ml water showed 77 and 9% mortality respectively. When one-tenth the label dosage of B. bassiana and “inert” carrier oil was combined with neonicotinoids clothianidin, imidacloprid, and dinotefuran applied in 1 ml water, there were significant increases (34, 30, and 68% respectively) in weevil mortality over the neonicotinoids alone 1 d after treatment. When one-tenth the label dosage of “inert” carrier oil alone was combined with neonicotinoids clothianidin, imidacloprid, and dinotefuran applied in 1 ml water, there were also significant increases with clothianidin and dinotefuran (38 and 24% respectively) in weevil mortality over the neonicotinoids alone 1 d after treatment. B. bassiana and its “inert” carrier oil provided 28, 50, and 78% mortality at the highest label dosage and 47, 76, and 89% mortality at 4× the highest label dosage in turf plug assays at 7, 10, and 14 d after treatment. Addition of 5 or 20% MycoMax (a nutrient source for B. bassiana) did not significantly increase mortality in turfgrass plug assays.

ELISA plates were used to determine the amounts of clothianidin and imidacloprid in Poa annua clippings from treated golf course fairways. Amounts of clothianidin ranged from 71.8 to 1238.1 ng/g tissue in 2011 and 68.8 to 2045.0 ng/g tissue in 2012. Amounts of imidacloprid ranged from 40.8 to 1679.2 ng/g tissue in 2011 and 116.8 to 3722.0 ng/g tissue in 2012. Listronotus maculicollis adults were caged on neonicotinoid and neonicotinoid/pyrethroid treated P. annua plugs. Substantial feeding on P. annua was observed; however, mortality of L. maculicollis adults was not significantly different from control plugs. We were not able to determine concentrations of either clothianidin or imidacloprid that were effective in controlling larvae. Our data help to explain the lack of control of this insecticide resistant pest.

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