“Try to time the spray for warm weather in mid-March. You can improve your chances for spray effectiveness by looking at the progression of pupae development. When you squeeze them and they begin to pop pink or red, instead of white, they are close to becoming adults. Remember that we are timing the spray to kill adults, so you should try to hold off your spray until most of the pupae are developed or some have emerged.”

• Fields that are severely infested with Hessian fly from the fall generation and are planted with a susceptible variety.

Unfortunately the best option for some fields will be to till them up. Fields approaching a 100 percent rate of infested tillers with plants that are dying or dead will fall into this category.

Hopefully, a high majority of wheat planted in the Southeast has some built in resistance to Hessian fly. Even so, recent research at Purdue University indicates some resistant varieties are breaking down in the presence of high and repeated populations of Hessian fly.

Although fly populations are suppressed by resistant wheat varieties, the insect has been able to evolve new races (biotypes) that can survive on and injure wheat plants with resistance genes, thus reducing effectiveness on control.

The Purdue-USDA study describes research to determine the frequency of resistance-breaking (virulent) biotypes in Hessian fly populations in the Mid-South and Southeastern U.S. and their response to wheat germplasm lines with 11 resistance genes that are being investigated in the Purdue/USDA program.

Laboratory research identified the major Hessian fly biotypes in 13 populations collected from Arkansas, Georgia, Illinois, North Carolina, and Virginia and determined shifts in virulence to resistance genes in these populations.

Results demonstrated that all genes presently incorporated into soft winter wheat varieties grown in the eastern U.S. are ineffective except in the extreme Southeast.

Newer resistance genes varied in effectiveness to the Hessian fly populations, but 7 of the 11 genes were highly resistant to the populations studied.

This information is vital to researchers developing wheat varieties for the Mid-South and Southeastern states, and will aid entomologists and wheat breeders in determining the most effective way to use resistance genes or gene combinations in the future to prolong their usefulness in controlling the Hessian fly.

(Dominic Reisig reported on the developing problem earlier in the year. For that, see Hessian fly problems apparent in North Carolina wheat

To keep an eye on the ever-changing insect situation in the North Carolina area, visit his blog site at http://www.nccrops.com/).

rroberson@farmpress.com