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United States Department of Agriculture

Agricultural Research Service


item James, Rosalind
item Elzen, Gary

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/17/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Imidacloprid and Beauveria bassiana are both pesticides used to control the silverleaf whitefly in melons and cucumbers. Imidacloprid is a chemical compound, and Beauveria bassiana is a fungus that causes white muscardine disease in insects. If growers could use both of these pesticides on the same fields, it could increase the flexibility they have in controlling this pest. Using two experiments, we tested to see if these pesticides would improve control when used together. In the first experiment, the two pesticides were sprayed onto plants infested with whiteflies. In the second, potted plants were soil-drenched with imidacloprid four days before they were infested with whiteflies. The fungus was applied as a foliar spray after nymphs developed. For both experiments, we used two application rates, and the insecticides were applied alone and in combination. When imidacloprid and white muscardine disease were combined, an inhibitory effect was seen. That is, imidacloprid was more effective alone than in combination with the fungus. For example, using pesticide concentrations equal to field rates, the fungus gave 81% control of whiteflies and imidacloprid gave 100% control. When the two were combined, we got 97% control. Using the same rate of imidacloprid, but reducing by half the amount of pathogen applied, resulted in more whiteflies being killed (99.3% control). Researchers have previously considered combining these two pesticides to try to improve whitefly control and reduce the total amount of pesticide used. In addition, combining pesticides can be used to reduce the potential for insects to develop resistance to chemical insecticides. Our results indicate that combining these pesticides does not improve control, and in fact, can reduce the activity of imidacloprid.

Last Modified: 10/17/2017
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