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Controlling Bean Leaf Beetles

May 10, 2002
Although it seems a bit silly to be talking about insecticides for control of bean leaf beetles (Table 2), at least a few fields of soybeans have been planted. Consequently, they will be at risk when bean leaf beetles find them. The beetles don't have much to choose from right now, so any seedling soybeans will have to do.

As I indicated in last week's Bulletin (issue no. 6, May 3, 2002), insecticides are warranted when densities of bean leaf beetles reach 16 per foot of row in the early seedling stage or 39 per foot of row at stage V2+. These thresholds are based solely on the potential damage resulting from defoliation and have no bearing on the situation with bean pod mottle virus. Based on what I have learned from the entomologists and plant pathologists at Iowa State University, the situation with bean leaf beetles and bean pod mottle virus is real (especially in western Iowa), although still not thoroughly understood. The situation in Illinois is uncertain. However, Marlin Rice, Extension entomologist at Iowa State University, has made the following qualifiers quite clear: "The qualifier for insecticide treatment is the presence of beetles and a history of bean pod mottle virus in the field (or adjacent field when rotated). Without the confirmation of the virus (late-season green stem or discolored beans from last year), then the application of an insecticide to prevent the insects/disease cannot be justified, in our opinion."--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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