An Emerging Wheat Pest in Louisiana

Fangneng Huang, Stephen Harrison, B. Rogers Leonard, Mukti Ghimire and Paul P. Price III

Hessian fly is one of the most destructive pests of wheat worldwide. This pest was first detected in the United States on Long Island, N.Y., in 1778, and is thought to have been introduced to this country by the Hessian soldiers during the Revolutionary War. Hessian fly may feed on rye, barley and wild grasses, but wheat is the preferred host. The larvae usually feed on the stem at the joints under the leaf sheath (See photo), which prevents elongation and nutrient transportation. Stunted stems may lead to plants breaking or lodging, reduced grain fill and even death, especially in early plant growth stages. The number of generations of Hessian fly per year in Louisiana is unknown, but four to six generations may occur each year in the southern United States.

Serious Hessian fly problems are usually associated with susceptible wheat varieties, summer double-cropping in reduced-tillage production systems, increased wheat acreage, early planting and mild winter temperatures. Among these, wheat variety susceptibility to Hessian fly is often the most important factor.

Hessian fly occasionally has been observed in Louisiana wheat fields but has not been a yield-limiting problem until recently. Wheat is planted in fall and harvested the following spring. During the 2007-2008 crop season, Hessian fly seriously damaged wheat in many fields across Louisiana. Yield losses were estimated to be 60-80 percent in some south Louisiana fields. Planting Hessian fly resistant wheat varieties appears to be the most effective strategy for managing this pest.

Hessian fly was not a significant problem in Louisiana before 2007; therefore, research evaluating management strategies is limited. Hessian fly resistance historically has not been considered an important factor when Louisiana producers select wheat varieties. 

LSU AgCenter scientists conducted field trials to clarify the occurrence and damage of Hessian fly on wheat and to provide information on genetic resistance to local Hessian fly populations. To do this, 26 wheat varieties were selected from the LSU AgCenter wheat performance trials and evaluated for the presence of and injury by Hessian fly at two locations during the 2008-2009 crop season. For details, see the Hessian fly table.

Location one was a wheat field at the LSU AgCenter Macon Ridge Research Station near Winnsboro, La. This field was managed to maximize over-summering of Hessian fly populations. Location two was a producer’s field near Maringouin, La. Many wheat fields in this area were severely damaged by Hessian fly during the 2007-2008 crop season. Natural Hessian fly populations in both trials were high, and susceptible wheat varieties were damaged heavily during spring 2009, particularly in the trial near Maringouin. See the photos.

The relative occurrence of Hessian fly for a given variety was generally consistent between the two locations. Six of the seven varieties with the lowest fly populations and four of the seven varieties with the highest insect populations were the same in both locations. The number of larvae and pupae on the seven varieties with lowest Hessian fly populations in the trial near Winnsboro ranged from zero to 1 insect per plant. Of the seven varieties with the highest Hessian fly populations, numbers ranged from 3.8 to 6.6 insects per plant. In the trial near Maringouin, the number of larvae and pupae on the seven varieties with lowest Hessian fly populations ranged from zero to 0.9 insects per plant, while the larvae and pupae on seven varieties with the highest populations ranged from 5.7 to 9.9 insects per plant.

Overall, grain yield was higher in the Winnsboro trial than in the Maringouin trial. Yield was negatively correlated to the relative Hessian fly populations in both locations, especially during the early growth stages. Yield of the seven varieties with the highest yields in Winnsboro ranged from 71 to 74.9 bushels per acre, while the seven varieties with the lowest yields ranged from 41.1 to 56.5 bushels per acre.

In the Maringouin trial, yield of the seven varieties with the highest yields ranged from 37.5 to 73.5 bushels per acre, while the seven varieties with the lowest yields ranged from 2.2 to 5.9 bushels per acre. The lowest yield, incidentally, was 97 percent lower than yield for the resistant variety in the trial. Several varieties with the smallest populations of Hessian fly also demonstrated good yield performance in both trials.

The results of these trials demonstrate that high yielding and Hessian fly resistant varieties are available in Louisiana. Additional wheat varieties are being evaluated, and LSU AgCenter scientists are conducting field trials to evaluate seed treatments and foliar-applied insecticides. Data from these studies will be used to develop effective strategies for Hessian fly management.

Fangneng Huang, Associate Professor, Department of Entomology; Stephen Harrison, Walker T. Nolin Professor of Agronomy,School of Plant, Environmental & Soil Sciences; B. Rogers Leonard, Professor and Jack Hamilton Chair in Cotton Production, Macon Ridge Research Station; Mukti Ghimire, Research Associate Specialist, Department of Entomology; and Paul P. Price III, Extension Associate, Macon Ridge Research Station.

(This article was published in the winter 2011 issue of Louisiana Agriculture Magazine.)