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A New Approach for Detecting Insecticide Resistance in Onion Maggot Populations 2002

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Project Leaders: B. A. Nault, Dept. of Entomology, NYSAES-Geneva

J. P. Nyrop, Dept. of Entomology, NYSAES-Geneva

A. M. Shelton, Dept. of Entomology, NYSAES-Geneva

R. W. Straub, Dept. of Entomology, NYSAES-Highland

Cooperators: J. Z. Zhao, Dept. of Entomology, NYSAES-Geneva

J. van der Heide, NYS Cooperative Extension, Oswego County

C. MacNeil, NYS Cooperative Extension, Ontario County

C. Hoepting, NYS Cooperative Extension, Lake Plains Veg. Prog.

M. Ullrich, NYS Cooperative Extension, Orange County

Type of Grant: Monitoring, forecasting, and economic thresholds

Project Locations: Research was conducted in several of the major onion growing regions in NY; therefore, results are applicable throughout NY and perhaps the eastern US.


The goal of this research is to develop a rapid assay for identifying insecticide resistance in onion maggot populations. Development of an assay in which larvae can be tested for resistance to insecticides ultimately will be used to predict controllability of onion maggot infestations in the field. In 2002, chlorpyriphos (Lorsban) was evaluated for managing onion maggot infestations in 12 commercial onion fields, which represented regions in eastern, central and western New York. Control differed considerably among fields in each of these regions. Lorsban tended to provide acceptable onion maggot control only when infestation levels were low to moderate (<20% plants killed in untreated control. Although populations have not yet been tested for Lorsban resistance using the new assay, we suspect that high infestations of onion maggot (>20% plants killed in untreated control) are resistant to Lorsban based on limited data using the old assay (target adults). Additionally, results from field experiments in 2001 and 2002 suggest that if an onion maggot infestation in a non-rotated onion field is not controlled effectively using Lorsban, then it is unlikely that Lorsban will effectively control it the following season. For this reason, we believe that onion maggot populations are relatively localized.

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