Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2007
Publication Date: 6/1/2007
Citation: Yee, W.L., Oriki, J., Nash, M. 2007. Mortality of Rhagoletis pomonella (Diptera: Tephritidae) exposed to field-aged spinetoram, GF-120, and azinphos-methyl in Washington state. Florida Entomologist 90:335-342. Interpretive Summary: Apple maggot fly is a serious quarantine pest of apple that has established in commercial apple-growing areas in central Washington. Knowledge about the effects of newer and safer insecticides is needed to manage the fly. Personnel at the Yakima Agricultural Research Laboratory in Wapato, WA, are determining the effects of aging the new semi-synthetic insecticide DE-175 and the organic insecticide bait GF-120 on mortality of the fly. Fresh DE-175 was as toxic to adult flies as the industry standard Guthion that was aged in the field, but DE-175 showed reduced toxicity after 7 days of aging. However, fresh and aged DE-175 reduced or eliminated injury to apple, comparable to Guthion. GF-120 was also highly toxic to flies, but showed reduced toxicity after 7 to 14 days of aging. The results of this study are important in that they indicate DE-175 and GF-120 show promise as alternatives to harsher materials for controlling apple maggot infestations, but that their residual toxicities first need to be improved before they can be used by themselves under the hot dry conditions of central Washington.
Technical Abstract: The new semi-synthetic spinosyn insecticide DE-175 (Dow AgroSciences, Indianapolis, Indiana) was tested for the first time against the apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae). Effects of field-aging DE-175 (formulated as a 100 g/L suspension concentrate) and other insecticides on apples in central Washington on the mortality of flies in the laboratory were determined. Mortality caused by DE-175 (100 g a.i./ha) aged 7 d was significantly reduced compared with that caused by fresh DE-175. DE-175 (100 and 75 g a.i./ha) aged for 7 d caused as much or slightly less mortality than spinosad (Entrust) (100 g a.i./ha)aged for 7 d. Fresh DE-175 and azinphosmethyl aged 7 or 14 d caused similar mortality, but aged DE-175 and spinosad caused less mortality than azinphosmethyl. Among insecticides, numerically the highest numbers of stings were seen in apples treated with DE-175 aged for 14 d, and the fewest in apples treated with azinphosmethyl. Control apples produced the most larvae, but apples treated with DE-175 (75 g a.i./ha) aged 7 d and with spinosad also produced a few larvae. However, no larvae emerged from DE-175 (100 g a.i./ha) aged 0, 7, and 14 d. Effects of field-aging GF-120 Fruit Fly Bait on apple leaves in central Washington were tested in a separate experiment. Fresh, 3-d, and 7-d old GF-120 caused greater mortality than 14-d old GF-120. Results show that DE-175 and GF-120 when fresh are highly toxic to R. pomonella, but that both have relatively short residual activities under the hot, dry conditions of central Washington in summer. Ingredients that prolong their toxicities or make their toxins available to flies longer may be needed to optimize their performance against flies in this region. Results also suggest that adult mortality is not an accurate predictor of infestation rates in apples and that the effects of DE-175 and GF-120 on larval control in this region need to be studied.