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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #222241
Title: Assessment of Knack Field Performance Through Precision Field and Laboratory Bioassays in Cotton

Author
item ELLSWORTH, PETER - UOFA, TUCSON, ARIZONA
item BARKLEY, VIRGINIA - UOFA, TUCSON, ARIZONA
item DENNEHY, TIM - UOFA, TUCSON, ARIZONA
item DEGAIN, BEN - UOFA, TUCSON, ARIZONA
item ELLINGSON, BOB - UOFA, TUCSON, ARIZONA
item Naranjo, Steven
item SIMS, MARIA - UOFA, TUCSON, ARIZONA

Submitted to: Laboratory Publication
Publication Type: Other
Publication Acceptance Date: 3/15/2007
Publication Date: 11/10/2007
Citation: Ellsworth, P.C., Barkley, V., Dennehy, T., Degain, B., Ellingson, B., Naranjo, S.E., Sims, M. 2007 Assessment of Knack Field Performance Through Precision Field and Laboratory Bioassays in Cotton. Laboratory Publication. P. 1-15

Interpretive Summary: Bemisia tabaci (whitefly) is a major pest of cotton and other crops in Arizona and insecticides play a critical role in control. When an insecticide performs different than expected, biological, ecological, and operational factors should be examined. Genetic resistance to the pesticide itself is often a concern. The control interval depends on the ecological impact of biotic (e.g., natural enemies) and abiotic (e.g., severity of storms) factors. Timing, rates, and application methods used are also important. A four-year study to evaluate pyriproxyfen field performance in Arizona was initiated in 2004 at grower sites in Maricopa, Buckeye, Wellton, and Marana. Resistance bio-assays were conducted on progeny of field-collected adults, pre- and post-spray. New eggs were marked in-field prior to spraying and examined in the field and lab to isolate direct pyriproxyfen-associated mortality from ecological factors. Nymphal bioassays were used to evaluate metamorphosis inhibition. Study results suggest pyriproxyfen field performance and resistance has not changed among years or locations. Work will continue in 2007 to identify factors that contribute to whitefly outbreak conditions. These data will be key to understanding any performance changes, either due to operational or ecological factors or due to innate changes in whitefly susceptibility. This will help advise growers about risks associated with whitefly outbreaks and lead to recommendations for minimizing these risks.

Technical Abstract: A four-year study to evaluate pyriproxyfen field performance in Arizona was initiated in 2004, after levels of whitefly (Bemisia tabaci) susceptibility in statewide surveys were observed to be decreasing. Grower sites in Maricopa, Buckeye, Wellton, and Marana were used. Resistance bio-assays were conducted on progeny of field-collected adults, pre- and post-spray. New eggs were marked in-field prior to spraying and examined in the field and lab to isolate pyriproxyfen -associated mortality caused by direct toxicity and ecological factors. Nymphal bioassays were used to evaluate metamorphosis inhibition. Study results suggest pyriproxyfen field performance and resistance has not changed among years or locations. Work will continue in 2007 to identify factors that contribute to whitefly outbreak conditions. These data will be key to understanding any performance changes, either due to operational or ecological factors or due to innate changes in whitefly susceptibility. This will be important in advising growers about the risk factors associated with whitefly outbreaks and should lead to recommendations for minimizing these risks.