Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 2010
Publication Date: April 13, 2010
Repository URL: http://hdl.handle.net/10113/48541
Citation: Knight, A.L. 2010. Cross-Resistance Between Azinphos-methyl and Acetamiprid in Populations of Codling Moth, Cydia pomonella (L.)(Lepidoptera: Tortricidae), from Washington State. Pest Management Science 2010; 66:865-874. Interpretive Summary: Codling moth, Cydia pomonella (L.), is the key insect pest of apple and pear. It has been intensely managed with the organophosphate (OP) insecticides for 50 years and some populations have developed OP resistance. New management programs have been developed and implemented which rely more heavily on other classes of insecticides, but cross resistance among these classes of insecticides has impacted the effectiveness and structure of new programs in some regions. A prerequisite for developing effective resistance management strategies for these compounds is to establish their current levels of effectiveness. ARS researchers at the USDA, ARS, Yakima Agricultural Research Laboratory, Wapato, WA surveyed 20 moth populations in Washington State and found significant differences among populations to OP and cross resistance with several alternative classes of insecticides. These results support a concern that alternation of insecticides with different modes of action may not be a sufficient strategy to avoid the evolution of broad spectrum insecticide resistance by codling moth.
Technical Abstract: Adult and neonate larval assays were conducted to assess the response of field-collected codling moth, Cydia pomonella (L.), populations from apple. Male codling moth populations exhibited a range of responses to a discriminating concentration of azinphos-methyl in a survey of 20 populations. Populations from certified-organic were more susceptible than from conventional orchards. Several additional studies were conducted with six populations that spanned the breadth of azinphos-methyl susceptibility. Male response’s (LD50’s) to azinphos-methyl and acetamiprid varied significantly among populations and were correlated. Mean fecundity was inversely related to azinphos-methyl tolerance. The residual effectiveness of field-applications of both insecticides varied significantly against neonate larvae. Neonate bioassays with insecticide-dipped fruit found significant differences among populations with azinphos-methyl, acetamiprid, methoxyfenozide, and spinosad; but not to esfenvalerate. These results support a concern that alternation of insecticides with different modes of action may not be a sufficient strategy to avoid the evolution of broad spectrum insecticide resistance by codling moth.