Remember to Wait for Wheat Fly Free Date - U of I Extension

News Release

Remember to Wait for Wheat Fly Free Date

This article was originally published on September 13, 2010 and expired on October 30, 2010. It is provided here for archival purposes and may contain dated information.

Wheat acreage will likely be down in the state for 2011, following 2009 & 2010's exceptional "shock to the agricultural system." However, the crop will undoubtedly be present in our area and that means an annual warning is once again needed.

During the late summer and early fall, the central Illinois area experiences egg laying by the second generation of Hessian fly. Without treating the situation properly, the hatching larvae can eventually damage wheat planted before the fly-free date.

The Hessian fly emerges in the spring and lays eggs on the leaves of wheat plants. Eventually, these eggs hatch, the larva pupate, and the resulting adult emerges as the second generation of Hessian fly.

When Hessian flies begin to lay eggs in the late fall and early spring, there is very little that producers can do to stop the pest since chemical control is often impractical. The only remaining options are to either plant after the fly free date or to use resistant varieties. A third option, a preferable option, is to do both.

By drilling wheat after the fly free date, the emerging wheat plants are not present for egg laying, and the adult fly dies long before it can infest seedlings. However, should a susceptible variety be planted before the date, the eggs will hatch in the spring, and the larvae will feed between the leaf and the sheath of the plant, causing extensive damage.

When managing Hessian flies, all wheat stubble and volunteer wheat should be destroyed, resistant varieties or moderately resistant varieties should be used, and the fly free date should be observed no matter what type of wheat variety is planted. Hession fly-free dates range from September 17 – October 12. For a listing of fly free dates, visit your local Extension office to view their Illinois Agronomy Handbook.

Source: Matt Montgomery, County Extension Director,

Pull date: October 30, 2010