Pesticides used against Cydia pomonella disrupt biological control of secondary pests of apple
2016
Beers, Elizabeth H. | Horton, David R. | Miliczky, Eugene
The effects of codling moth (Cydia pomonella (Linnaeus)) (Lepidoptera: Tortricidae) management programs on secondary pests of apple were examined from 2008 to 2011 in five replicated large-plot trials. The orchards were chosen for a history of Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) and tetranychid mite outbreaks. Programs covered the first, second, or both generations of C. pomonella, and employed some of the newer insecticides for comparison to older materials. Increased levels of E. lanigerum were consistently associated with the use of spinetoram and novaluron throughout the tests. The mechanism of disruption was not completely clear, but suppression of Forficula auricularia Linnaeus (Dermaptera: Forficulidae) and Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) were associated with the use of these materials. Methoxyfenozide, chlorantraniliprole, and azinphos-methyl did not disrupt biological control of tetranychid mites or aphids, and negative effects on natural enemies were infrequent. Lambda-cyhalothrin provided direct control of aphid species, thus reduced levels of natural enemies could also be ascribed to lack of prey. The effect of some of the insecticide applications made during the first generation were evident for many months after the application in terms of pest and natural enemy populations; however, attempts to mitigate disruptive effects by shifting the use of materials to the second generation of C. pomonella were not successful. The effect on biological control of tetranychid mites was less consistent, although some detrimental effects (increased pest or decreased predatory mite levels) were associated with spinetoram, novaluron, and lambda-cyhalothrin. The difficulties in sampling natural enemies and determining their impact made pest outbreaks the most reliable indicator of pesticide-induced disruption.
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