Submitted to: Eastern Wheat Workers and Southern Small Grain Workers Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/4/1999
Publication Date: N/A
Citation: N/A Interpretive Summary: The Hessian fly is a destructive pest of wheat throughout the United States. The fly is controlled primarily by use of resistant wheat varieties and cultural control methods that reduce the availability of wheat during critical periods of the insect's life cycle. Although resistant varieties are the most reliable and economically feasible method of control, their use, over time, results in development of Hessian fly races (biotypes) that can attack resistant plants and reduce the stability of resistance in varieties. To counter this problem, new sources of resistance are continually investigated by USDA, ARS and University scientists to identify additional genes. Useful genes are then incorporated into improved wheat varieties. Hessian fly populations from the eastern U. S. soft winter wheat region and from soft winter and spring wheat regions of Idaho and Washington were sampled regularly to monitor genetic changes in the insect. Populations were studied to determine their biotype composition and response to new resistance genes under investigation in wheat breeding programs. Research demonstrated that fly populations continue to evolve in response to exposure to resistance genes in wheat varieties, especially in the southeastern states. Research also demonstrated reduced effectiveness of some new resistance genes to fly populations from the extreme southeastern U. S. and some areas of Idaho and Washington. Continued research on the genetics of resistance in wheat and virulence in the insect is essential in order to provide wheat growers with stable sources of resistance in the future.
Technical Abstract: The Hessian fly, Mayetiola destructor (Say), is a destructive pest of wheat in all major wheat-growing areas of the United States. Since the 1950's resistant cultivars have provided the most reliable and economical form of control of this pest. The existence of Hessian fly biotypes capable of infesting resistant wheat cultivars has been known for many years and long-term stability of resistance is a concern. An extensive program to sample wheat for Hessian fly was begun in the late 1980's in order to monitor genetic changes occurring in fly populations from major U. S. wheat-growing regions. By the early 1990's Hessian fly populations in many states in the Midwest, mid-Atlantic and mid-south were predominantly biotype `L', while populations in the Southeast still were undergoing change. Present research with populations from southern and Midwestern states (AL, AR, GA, IL, IN, NC, VA) and Idaho and Washington, provided similar data but demonstrated that development of biotype `L' had not continued in the lower southeast, as expected. As a result, wheat cultivars carrying the resistance gene combination H7H8 remain effective in this portion of the eastern U. S. wheat-growing region. The development of virulence to resistance genes in Hessian fly populations from Idaho and Washington was similar to that occurring in populations from Midwestern and Mid-Atlantic States. Virulence to the new resistance gene H13 was demonstrated in fly populations from mid-Atlantic states, but did not occur in populations from Midwestern states or northern sections of southern states such as AL, AR, or GA.