Author
 |
RATCLIFFE, ROGER |
|
Submitted to: National Association of Wheat Growers Proceedings
Publication Type: Proceedings Publication Acceptance Date: 4/10/1998 Publication Date: N/A Citation: N/A Interpretive Summary: The Hessian fly is a destructive pest of wheat that occurs in all major wheat growing areas of the United States. Farmers control the Hessian fly primarily by growing resistant wheat varieties and by practicing cultural control methods that reduce the availability of wheat during critical periods of the fly's life cycle. The most important cultural control methods are delayed seeding of winter wheat to escape fall infestation by the fly, and destruction of volunteer wheat. Both practices reduce the amount of wheat available for egg laying by adults in the fall, and, in turn, the number of larvae present to attack fall-seeded wheat. Resistant varieties, which are a form of biological control, and cutural control methods have no adverse affects on the environment, pose no health threats to humans, and are economical to use. The extensive use of resistant wheat varieties, however, results in development of Hessian fly races that are capable of attacking resistant wheat varieties and reducing the long-term stability of resistance. To counter this problem, additional sources of resistance are continually investigated by USDA, ARS and University scientists to identify new resistance genes. Presently, fifteen sources of Hessian fly resistance have been incorporated into wheat varieties or experimental wheat lines that are available to public and commercial wheat breeders. Resistant varieties provide a built-in source of Hessian fly control that often is the first line of defense for farmers, especially when cultural control measures are less effective or are difficult to maintain. Continued research on the genetics and breeding 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 throughout the world. In the United States the insect occurs in all major wheat-growing areas from the Atlantic Coast to the Great Plains and parts of California, Idaho, Oregon, and Washington. Wheat is the preferred host of the Hessian fly. The typical life cycle of the fly begins with fall emergence of adults from infested wheat stubble or volunteer wheat. The female oviposits on the upper leaf surface of plants. Larvae crawl to the crown of the plant where they feed. Most larvae become full grown before the onset of cold weather. The following spring, larvae transform to pupae, and adults emerge and infest wheat about the time the plants begin to joint. The most important methods of controlling Hessian fly are planting resistant wheat varieties, delayed seeding of winter wheat to escape fall infestation, and destroying volunteer wheat. Resistant varieties have provided the most reliable and economical control. Twenty-seven major genes designated H1 through H27 have been described. The existence of Hessian fly biotypes capable of infesting resistant wheats has been known for many years and long-term stability of resistance is a concern. Because Hessian fly resistance genes may eventually be rendered ineffective by virulent fly biotypes, additional sources of resistance are continually investigated. The future of Hessian fly management on wheat is promising, but will require continued research to improve durability of resistance and to stay abreast of changes in Hessian fly populations. |
