|Beers, Elizabeth - Washington State University|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2016
Publication Date: 5/24/2016
Citation: Beers, E., Horton, D.R., Miliczky, E. 2016. Pesticides used against Cydia pomonella disrupt biological control of secondary pests of apple. Biological Control. 102:35-43.
Interpretive Summary: Regulatory changes affecting types of chemical insecticides available for use in apple orchards of Washington State have prompted efforts to examine effects of replacement insecticides on biological control of orchard pests. Researchers at USDA-ARS Wapato in Washington, in collaboration with a scientist from Washington State University examined the effects of some newer insecticides on biological control and outbreaks of secondary pests in commercial apple orchards in central Washington. This study showed that certain insecticides led to outbreaks of aphid and mite pests apparently through disruptive effects on natural enemies of aphids and mites. This information will help apple growers better understand the possible effects of certain insecticides on biological control of secondary pests in their orchards.
Technical Abstract: The effects of codling moth 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 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 and Aphelinus mali were associated with the use of these materials. Methoxyfenozide, chlorantraniliprole, and azinphos-methyl did not disrupt biological control of tetranychid mites or aphids. 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 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.