No. 1 Article 8/March 23, 2007

Hessian Flies Should Be on Our Radar Screens

The following paragraphs are from an article in the March 7, 2007, issue of Purdue University News by Dr. Omprakash Mittapalli, currently a postdoctoral fellow at the Max Planck Institute for Chemical Ecology in Jena, Germany. His topic is the research being conducted by Dr. Richard Shukle, a USDA-ARS entomologist and Purdue adjunct assistant professor, and his colleagues. Shukle is working to learn more about how the flies feed and why they can't establish a feeding site on plants that are resistant to the larvae. Dr. Mittapalli was a former graduate student in Shukle's laboratory. Purdue University, USDA-ARS, and the USDA Current Research Information System provided support for the project.

"Hessian flies have been in the United States for more than 200 years," writes Dr. Mittapalli, "apparently accidentally introduced by German mercenaries during the Revolutionary War. The flies are found worldwide, but the U.S. infestation has been mainly in the Southeast. In Georgia during the 1980s, wheat crop losses totaled $28 million in one year when the insect overcame the plant's resistant gene that was being used at the time.

"Over the past two years, the pest also has caused extensive yield losses in southeastern Missouri and a resurgence occurred in Oklahoma in 2006. Most recently, a Hessian fly infestation was identified near Lafayette, Ind., where the insect hadn't been reported for more than a decade."

This information is a heads-up for everyone who will be scouting wheat this spring. We will want to take note of any infestations of Hessian flies that occur. We haven't had to worry much about this pest in recent years, but every now and again, a new Hessian fly biotype develops with the ability to overcome the genes for resistance in resistant varieties of wheat. So be watchful for symptoms of Hessian fly injury to wheat plants--stunted, dark green plants with erect leaves and thickened stems. During the spring moths, the Hessian fly is in its "flaxseed" (puparium) stage of development as the maggot develops to an adult fly (black and very small--about 1/8 inch). It's possible that some of the plants that were infested last fall may not have survived the winter.

Hessian fly pupa ("flaxseed," left) and larva (right) at the base of a wheat plant. (Photo courtesy of Kevin Black, Growmark, Inc.)

If you encounter infestations of Hessian flies or have some suspicions, contact us. We'd like to share such information with our colleagues in West Lafayette.--Kevin Steffey

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