Well the Cotton Conference is over and seemed to be a big success with more than 350 individuals in attendance. Grain sorghum planting is well underway and moisture conditions remain good in most areas. Wheat is maturing quite rapidly. Really, we are a little ahead of schedule on wheat maturity. The past two freezes have caused some damage to area wheat fields but no widespread problems like to the south of us. Apparently several thousand acres of wheat south of Melvin sustained significant damage from the freezes.

Area wheat fields are showing signs of moisture stress and a lack of fertility. Many fields are showing signs of nitrogen deficiency. Leaf rust has been a problem in many fields and damage is really evident now in those fields which were not treated. It is very tough making those treatment decisions in dryland wheat.

We have found several wheat fields just North of Rowena heavily infested with Hessian Flies. This is the first documented case of infestations of Hessian flies in Runnels County. Due to the location of the infestation, the life cycle of the insect, the poor mobility, as well as several other factors, the pests were probably brought into this area last year on combines which have been harvesting wheat in counties east and south of here.

Producers in this area are encouraged to inspect their wheat fields for the presence of Hessian flies. Some of the heavily infested wheat fields are currently being plowed up and wheat straw being turned under. Producers are highly encouraged to make sure combines which have been used in infested areas are throughly cleaned of wheat straw prior to moving into your wheat field. Clean Them Out before moving the equipment back into the area. They oversummer in the wheat straw.

Life Cycle
The insect overwinters in the larval stage within a puparium on stubble, volunteer wheat, early planted wheat and other host grasses. Puparia can also become a part of the soil surface organic debris originating from infested seedlings killed by the larvae.

Because of their resemblance to flaxseed, the puparia are often referred to as the “flaxseed stage” of the pest. Adult Hessian flies emerge as temperatures reach a mean of 45 to 50 degrees F. Spring emergence, once initiated, extends over
several weeks. This extended emergence protects the insect against population destruction in the event of sudden unfavorable weather. The occurrence of multiple generations in Texas increases the possibility of crop damage and major field losses.

The adult Hessian fly is similar in appearance and size to a small mosquito. The life span of an adult is generally no more than 3 days. After emergence, males quickly find receptive females. Actual mating requires only 10 to 20 seconds. Oviposition usually begins within 1 to 2 hours after mating and is completed within 1 to 2 days. Females prefer to oviposit on newly emerged young plants or leaves as opposed to older wheat plants.

Fecundity is variable, ranging from fewer than 40 to more than 450 eggs per female, with an average of about 200.

Host Plants
Wheat is the preferred host but infestations have been found on barley and triticale. Oats are not infested by this pest.

Delayed Planting— Late summer rains of about one inch trigger development of aestivating (oversummering) Hessian flies. About 10-12 days later, the first Hessian fly adults appear. At this time, flies can infest volunteer wheat or early planted winter wheat. Severe fall infestations are usually caused by the existence of two favorable conditions: an earlier than normal planting date and a Hessian fly-susceptible variety of wheat.

The use of resistant wheat varieties has been highly effective in reducing Hessian fly damage. Before developing Hessian fly resistance in wheat, tremendous yield losses occurred in Nebraska and other Plains states. Using resistant varieties alone, or in combination with delayed planting dates and destruction of volunteer wheat, has greatly reduced the fly as a major concern in most wheat-producing states. The primary resistance mechanism is antibiosis, where young larvae that initiate feeding on resistant plants are killed by natural substances in the plant. Even on resistant varieties, a small percentage of flies may survive to reproduce. Therefore, because of this gradual selection on virulent flies over a period of years, resistant varieties must be monitored continuously.

Insecticides
Insecticides registered for use at planting for Hessian fly control are not recommended. Because of the sporadic occurrence of severe infestations, the economics do not support insecticide use at planting. Delayed planting dates and resistant varieties can be used with little or no additional cost to the farmer.

You still have time to order your newsletter! “Pest Management News” is a newsletter which provides timely, accurate and pertinent information in the areas of crop production within the Southern Rolling Plains. Newsletters are written weekly during the growing season and a total of eighteen were issued in 2002. This newsletter will keep you abreast of current insect pest populations, natural enemies, biological and cultural control tactics and chemical control options. It will also provide the user with economic thresholds and other management tools to assist the farm operator in making management decisions. Currently, there is a $10 subscription fee to cover the cost of postage. If you are interested in receiving this newsletter during 2003, please send $10 to “Pest Management News,” P.O. Box 658, Ballinger, Tx 76821, payable to “Pest Management News” by April 19, 2003.

Larval, flaxseed and egglay pictures are from the Nebraska Cooperative Extension G73-46A (Revised October 1998) John E. Foster and Gary L. Hein Extension Entomologists
Adult Hessian Fly from ipmimages.org. Photo taken by Scott Bauer, USDA ARS

Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level, race, color, sex, religion, handicap or national origin. The information given herein is for educational purposes only. References to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.