Imported longhorned weevils in soybean

Imported longhorned weevils again have been found defoliating soybeans. For each of the past three summers, this insect has caused noticeable injury to soybean during late June and early July. Problems have always been associated with grass, either following CRP or migrating out of adjacent pasture. The weevils can strip all the leaves from V5 or smaller plants; older plants apparently produce leaves faster than the weevils can defoliate them. Injury I have seen has been confined to border rows or very small areas of the field.

These insects are difficult to kill with insecticides. One insecticide test I conducted in 1994 suggested that Lorsban 4E or Sevin XLR Plus gave better control than Pounce 3.2EC. The high rate of either Lorsban (2 pints/acre) or Sevin (2 pints/acre) should be used. For more detailed information on the biology of this insect, see the June 30, 1995, issue of ICM, page 120.

This article originally appeared in the July 14, 1997 issue, p. 141.

Prepared by Marlin Rice, professor, Department of Entomology
Iowa State University, Ames, Iowa.
This information subject to a usage policy.

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Last updated 7/9/97 by John VanDyk
http://www.ipm.iastate.edu/ipm/icm/1997/7-14-1997/impolhw.html