Fall and Spring Oviposition of the Alfalfa Weevil and the Proper Timing of Fall Insecticide Applications

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Abstract
The amount of fall oviposition of the alfalfa weevil, Hypera postica (Gyllenhal), in alfalfa fields in New York and the relative importance of fall-laid and overwintering eggs as compared with spring-laid eggs were investigated over a 2-year period. These data were used to determine the proper timing of fall insecticide applications for the most effective control. The percentage of successfully overwintering eggs was found to vary according to field location, snow cover, severity of winter, and alfalfa conditions. Early-spring larval populations were found to be significantly correlated with the number of eggs per stem collected during the previous winter. There was no correlation between December-collected eggs and the number of larvae sampled during late spring. Late-fall applications were perhaps most effective either because they controlled the fall population of adults that might have resumed position in the spring, or because the residues were still sufficient in the spring to reduce the adults and larvae that were active then.

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