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Corn Pith Weevil

September 7, 2001
As growers survey their corn crop this fall, they wonder why there is so much tip breakage. With a few exceptions, numbers have been low for both the European and southwestern corn borer. The majority of the breakage is above the ear; therefore, most growers probably won't get too excited until they notice that the damage is in both non-Bt and Bt hybrids. There are a number of things that can explain this type of tip breakage. This type of damage is usually a good indication that corn borers have been active, but diseases like anthracnose can cause tip dieback. Severe weather patterns and high winds can also cause localized damage. There is another cause that "old timers" tell me is common in southern Illinois, and that is the corn pith weevil.

The corn pith weevil is an interesting insect about which little has been written. It overwinters in its larval form buried in the soil. Adult weevils emerge from the soil in early July through early August. Eggs are laid during this period. Once hatched, the larvae feed in the upper parts of the cornstalk. Feeding continues until the first part of October, when the larvae leave the plant and enter the soil for the winter. There is only one generation per year.

This insect is not an economic factor in corn. The timing of the feeding coupled with the amount of tissue consumed makes any yield loss insignificant.--Mark Hoard

Author: Mark Hoard

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

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