Winter Wheat Planting
What’s the Buzz on the Hessian fly?
By Jeri Geren
Winter wheat planting is nearly upon us, and as tradition would have it, it’s about time to get to work in the field. To help insure this crop turns out to be something worthwhile, it’s important to take measures now that can improve the stand at harvest. One such measure is the prevention of the Hessian fly into the emerging wheat stand. This gnat-like fly is often ranked as the most important insect pest in winter wheat production. The injury it causes frequently goes unnoticed until harvest and infestations are fairly common in all but the very southwest portion of the state.
Wheat is the preferred host of the Hessian fly, but rye and barley may become infested to a lesser degree. The adult is a tiny, dark colored insect about 1/8 of an inch long. It emerges on warm fall days from August through November, generally following a rain. Females will lay eggs in the leaf grooves of fall seeded wheat. Within three to ten days, the eggs hatch and the larvae migrate downward between the leaf sheath and the stem stopping just above the crown. They move during the night when humidity is high and once they reach the bottom of the plant, they will withdraw sap from the plant for eight to 30 days. Most will mature before the onset of winter weather. The full-grown larvae gradually form brown, 1/8 inch long capsule-like cases commonly called “flaxseeds.” The insect will pass the winter in the flaxseed stage.
Overwintering pupae that produce the spring brood will become adults in late march and April. The spring maggots will attack the base of the plant or just above the nodes of jointing wheat. In addition, some of the “flaxseeds” will lie dormant in the stubble until they emerge to produce the main fall brood. There is yet another portion of the “flaxseeds” that will remain dormant for weeks, months or even years.
Some tips to help manage Hessian fly include destroying infested stubble, grazing or burning fields that have had high levels of injury, destroying volunteer wheat, rotating crops, planting after the best pest management, or fly-free date, using insecticide treated seed and planting resistant varieties. Also, it is important to note, that while planting after the best pest management date is essential for fall infestations, very delayed planting can increase the risk of a Hessian fly outbreak in the spring since females prefer laying eggs on smaller younger plants.
While we may not know what next year’s wheat crop will bring, at the very least, there are measures to take now to avoid Hessian fly infestations in the near future.