Date of Award

1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

First Advisor

David J. Boethel

Abstract

Insecticide toxicity to hemipteran predators (i.e. Geocoris punctipes (Say), Nabis capsiformis Germar, Nabis roseipennis Reuter, and Podisus maculiventris (Say)) was evaluated using three different routes of insecticide exposure (direct contact, indirect insecticide toxicity through consumption of treated prey, and residue uptake). Pirate 3SC$\sp\circler$ (chlorfenapyr) had direct contact toxicity equal to Ambush 2E$\sp\circler$ (permethrin) and Methyl Parathion 4E$\sp\circler$ to most hemipteran predators tested. Exposure to foliage treated with Proclaim 0.16E$\sp\circler$ (emamectin benzoate) usually resulted in lower mortality as compared to Pirate. Condor OF 100F$\sp\circler$ (Bacillus thuringiensis) had the lowest contact toxicity to hemipteran predators of all insecticides tested. Pirate at 0.224 kg AI/ha had significantly greater toxicity through consumption of treated prey than Proclaim to adult N. roseipennis and greater toxicity than Admire 2FS$\sp\circler$ (imidacloprid) and Tracer 4SC$\sp\circler$ (spinosad) to adult G. punctipes. Pirate displayed greater residual toxicity in the field than the standard insecticide, Ambush, to adult G. punctipes and N. roseipennis and both adult and third-instar nymphs of P. maculiventris. Proclaim had lower residual toxicity than Pirate to G. punctipes and N. roseipennis, but greater residual toxicity than Admire and Tracer to adult G. punctipes adults when foliage was collected 48 hours after insecticide applications. Generally, older classes of insecticides, such as organophosphates and pyrethroids, were more toxic to natural enemy populations than newer insecticides in field tests. Total predator populations were significantly lower in plots treated with organophosphates as compared to populations in untreated plots in 1993 and 1995. In 1993, plots treated with Orthene 75S$\sp\circler$ (acephate) had the lowest predator populations, and in 1995, plots treated with Karate 1E$\sp\circler$ (lamba-cyhalothrin) had the lowe st populations among insecticides tested. In general, newer classes of insecticides were less toxic to hemipteran predators than older, standard compounds. These results demonstrate that these newer, more selective compounds may enable soybean producers to use these insecticides to combat pests and preserve a larger proportion of resident beneficial arthropod populations which in turn should slow pest resurgence and prevent secondary pest outbreaks.

ISBN

9780591035018

Pages

97

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