Helmut Riedl

Lethal and sublethal effects of abamectin, spinosad, methoxyfenozide and acetamiprid on the predaceous plant bug Deraeocoris brevis in the laboratory

Deraeocoris brevis (Uhler) (Hemiptera: Miridae), an important generalist predator in pome fruits in the western United States, was reared in the laboratory on frozen Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs and treated in a Potter spray tower to assess acute toxicity and chronic sublethal effects of abamectin, spinosad, methoxyfenozide, and acetamiprid. Acute toxicity was assessed using topical application. Sublethal effects were examined as the combined result of topical, residual and oral exposure. Two different dose rates, the full field rate and 10% rate of the full field rate, were compared to distilled water as the untreated check. Methoxyfenozide and spinosad had no acute toxicity to nymphs and adults at the 10% and full field rate, and no effect on egg hatch and nymph survival just after hatch. Acetamiprid and abamectin at the full field rate did not affect egg hatch, but the residue had moderate to high toxicity to hatched nymphs. Also, topically applied acetamiprid and abamectin had moderate to high acute toxicity to nymphs and adults at the full field rate, but moderate toxicity at the 10% rate. In sublethal bioassays, abamectin-treated adults (10% field rate) laid 80% fewer and less viable eggs compared with the untreated check. Spinosad-treated (full field rate) adults laid fewer and less viable eggs. Also, egg hatch in the subsequent generation was lower. Methoxyfenozide had no sublethal effects on adults at the full rate, but slowed development of 4th instars following treatment of 2nd instar nymphs, and lowered fecundity by 30% in the subsequent generation compared with the untreated check. Acetamiprid (10% rate) applied to nymphs or adults had no effects on development or reproduction. Results from this study suggest that the newer reduced risk insecticides, which have begun to replace organophosphate insecticides in pome fruits in the United States, are not as selective to natural enemies as initially thought. Their impact on D. brevis varied with chemistry and mode of action from primarily acute toxicity (i.e., acetamiprid) to reproductive and other sublethal effects (i.e., methoxyfenozide, spinosad) or a combination of both (i.e., abamectin). In addition to acute toxicity, sublethal effects need to be quantified in order to accurately predict the total impact of a pesticide on a natural enemy in the field.

Attraction of adult Rhagoletis indifferens (Diptera: Tephritidae) to unbaited and odor-baited red spheres and yellow rectangles.

Abstract Five sizes of red spheres (4, 6, 8, 10, and 12 cm diameter) and 2 orientations of yellow rectangles (vertical and V) were evaluated as unbaited sticky-coated traps for western cherry fruit flies, Rhagoletis indifferens Curran, in unmanaged cherry trees in Washington and Oregon. Red spheres that were 10 cm in diameter attracted more flies than red spheres that were 8 or 12 cm in diameter and significantly more flies than 4- or 6-cm spheres and yellow rectangles of either orientation. In a 2nd test, red spheres (10 cm diameter) baited with ammonium carbonate alone or ammonium carbonate plus putrescine attracted significantly more R. indifferens than similar spheres baited with ammonium acetate alone, putrescine alone, 3-methyl-1-butanol alone, or combinations of these substances. In a 3rd test, vertical yellow rectangles baited with ammonium carbonate alone attracted numerically more R. indifferens than any of the aforementioned substances alone or in combination. We discuss the potential value of 10-cm red spheres baited with ammonium carbonate for monitoring and direct control of R. indifferens.