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Hessian Fly


Summary: Farmers and agricultural workers may experience severe damage to their wheat, barley, or rye crops because of Hessian flies. The infestation of these pests can best be avoided by planting wheat crops after the fly free date.

The Hessian fly is believed to have arrived in North America during the American Revolution. The Hessians were eighteen century German regiments that fought along side British troops against the American colonists during the American Revolutionary War. The Hessians may have accidentally brought with them a small insect that would hurt the farms of later generations of Americans.

The Hessian fly is known for the destruction it causes to growing wheat, rye, and barley plants. They are somewhat active in the fall, living only about three days. During this short period they mate and the females lay eggs. The eggs over-winter and emerge as adults in the spring, ready to wreak havoc on wheat crops.

The size of a Hessian fly is comparable to that of a mosquito. An adult male Hessian fly tends to have brown coloration, whereas an adult female Hessian fly will typically have red coloration. Eggs are white when they are laid, but later develop a brown shell. Its brown shell is often referred to as œflax seed. The maturing Hessian fly will attach itself to the stem of a wheat plant and absorb as much sap as it can. It will slide down the plant to eat the sap and cause a lot of damage to the plant in the process. In fact, the larvae eat so much food that it does not need to eat anymore as an adult. The Hessian fly will typically rest between the stem base and leaf sheath. The feeding results in wheat with stalks that break before the harvest.

With all the new technology invested in farming these days, Scientists have actually developed types of crops that resist the Hessian fly. There are thirty different genes that can be inserted into growing crops that help prevent infestation. However, as quickly as modified crops are introduced, it seems the Hessian fly has been able to develop resistance to the genetically modified crops. Each state has different sizes of populations of non-resistant Hessian flies, so checking with your state's agricultural extension service for the most accurate information would be advisable prior to planting.

Farmers have learned a few ways to avoid the Hessian fly infestation, though no method is completely foolproof. One method is to wait until late spring to plant wheat crops in order to avoid the newly emerging flies. Unfortunately, once crops are infested with Hessian flies, there are not many techniques to get rid of them. As with most other pest problems, prevention is the key. Insecticides are typically not used to control Hessian flies because if they are not sprayed at the correct time, the pesticide are ineffective.

Tips to Avoid Hessian fly Infestation:
¢ Do not plant wheat with heavy seeding rates.
¢ Destroy volunteer wheat.
¢ Avoid overuse of fertilization using nitrogen.
¢ Plant wheat crops after the fly free date. (In the fall, the fly free date can be as late as the middle of October, depending on the county of your state that you live in.)
¢ Practice crop rotation. Hessian flies are weak fliers and are unlikely to migrate to new fields.
¢ Avoid planting continuous no-tillage wheat-double-cropped soybeans.

Tips to Identify Plants Damaged by Hessian Flies:
¢ Look for leaves with a deep bluish-green color.
¢ Look for stunted wheat, rye, and barley crops.
¢ Hessian flies may have damaged plants with poor stands.
¢ Keep your eyes peeled for wheat plants with thicker stems.



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