As most of you are aware, Allen Knutson (Texas AgriLife Extension), Russell Sutton (Texas AgriLife Research), and I conducted a series of Hessian fly studies this past year to address the Hessian fly disaster we observed two years ago. We evaluated both seed treatments and wheat varieties. Following is a brief summary of our observations.
We planted this study in two locations, one in Grayson County, and one in Hunt County. We evaluated the following treatments (expressed as ounces of product per 100 pounds of seed): 1 and 2 ounces of Gaucho; and 1, 1.33, and 2 ounces of Cruiser. We observed grasshopper suppression with all of these treatments in the Hunt County location. However, follow-up sampling of the tillers in both locations showed that the seed treatments had no effect on the Hessian fly ó we found as many Hessian fly larvae and pupae in the tillers of the treated wheat as we did in the untreated wheat.
Resistant varieties are a recognized tactic for controlling Hessian fly in wheat. However, varietal resistance is effective in controlling some biotypes of Hessian fly and not others. We conducted two tests evaluating selected wheat varieties for resistance to the predominant races of Hessian fly in this region. We evaluated the following varieties for Hessian fly resistance: Pioneer 25R47, Pioneer 25R57, Coker 9553, Terral LA 841, AgriPro Crawford, AgriPro Fannin, Duster, and an experimental SRWW from TAMU (TX4A35). Duster and TX4A35 showed excellent resistance, and Crawford exhibited good resistance. All of the rest of the varieties were moderately to highly susceptible to Hessian fly. The following table summarizes our findings:
How do I effectively manage my wheat crop this fall to reduce the threat from Hessian fly?
There is no single tactic that will completely eliminate the threat of Hessian fly to the 2008-2009 wheat crop, but there are a number of things a producer can do to minimize the risk of this insect pest. We would suggest the following:
Delay planting as long as possible. Nov. 1 is a good target date, but we have seen only minimal fly damage to wheat planted after Oct. 25.
Destroy volunteer wheat in the field now. Volunteer wheat can harbor early emerging Hessian flies and greenbugs, and act as a bridge to infest later planted wheat. It is also a source of food for armyworms. We would like to see all volunteer wheat destroyed by the first week in October.
Hessian fly pupae oversummer in wheat stubble, so it pays to rotate your wheat crop. Plant behind corn, grain sorghum, soybeans, or cotton, if possible.
The resistant variety option here is not very useful. Duster is a hard red winter wheat with questionable straw strength, and Crawford is somewhat tolerant to Hessian fly, but not resistant. However, if you must plant early, these varieties should be considered.
Seed treatments were not effective on Hessian fly this past year. They will, however, provide fall greenbug suppression and provide protection from fall grasshopper infestations.