WEST LAFAYETTE, Ind. The Hessian fly, the world's No. 1 pest of wheat, has a curious genetic link to its favorite meal. Within a few years, after farmers identify resistant wheat varieties, the fly mutates and finds a way around the plants defenses.
But the fly's genetic tricks may be its undoing because Purdue University entomologist Jeff Stuart plans to use that genetic information against it to prevent future outbreaks of the pest.
Major infestations of the Hessian fly dont happen often, but when they do occur they can be devastating. For example, 1989 outbreaks in Texas and South Dakota caused an estimated $15 million and $30 million in damage respectively. Stuart says the fly is nearly ubiquitous.
After an area has been infested, farmers try to stop future outbreaks by switching wheat varieties and hoping this stops the fly from returning the next year. It's a hit-or-miss approach.
Stuart says it is not completely known how resistant varieties of wheat stop the fly, but it appears that the resistant wheat plants wall off living cells from the insect. This causes the Hessian fly larvae to starve.
Almost everywhere one grows wheat youll find this insect, with the possible exceptions of Australia and Japan, he says. The fly is out there, and when environmental conditions are just right, such as a cool, wet spring and if you have a field that had some volunteer wheat during the summer, the fly populations can take off and become a real problem.
If the Hessian fly couldn't mutate to get around wheat's defenses, the insect would die out because they can't feed on any other plant. Scientists can't even raise them in the laboratory on artificial diets. However, every time the Hessian fly mutates and develops a new way to invade wheat, wheat breeders have been able to identify and incorporate new Hessian fly resistance genes in new cultivars of wheat, and the battle between plant and animal begins anew.
When the mosquito-like H
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Contact: Steve Tally
tally@aes.purdue.edu
765-494-9809
Purdue University
18-Jan-2001