( arvae can alter the physiology and chan...)Scientists find genes involved in the battle between Hessian flies and wheat

On resistant plants, Hessian fly larvae encounter defense mechanisms that include poisonous oxygen compounds, Shukle said. These compounds, also called reactive oxygen species, can be produced either by the plant or within the Hessian fly larval digestive system. These poisons then disrupt the insects' gut function.

"The larvae probe the plant to open a sustained feeding site," said Jonathan Neal, a Purdue entomologist and another author of the paper. "Resistant plants block the larvae from establishing a feeding site. It's as if larvae keep trying to open doors because they are programmed to look for a feeding site.

"In resistant plants, the doors are all locked. Then the larvae finally crawl down to the base of the plant and die. This is death by frustration."

Hessian flies can be controlled by using specifically bred wheat varieties called resistant wheat cultivars. Infestations by the flies also can be prevented by planting wheat after the fly is no longer active and laying eggs. This "fly-free date" is set in different regions according to climate.

The study represents a step in understanding the complexity of antioxidant defense responses during interaction between Hessian flies and wheat, he said. It may also be applicable to other insect-plant interactions.

Hessian flies have been in the United States for more than 200 years, apparently accidentally introduced by German mercenaries during the Revolutionary War.

The flies are found worldwide, but the U.S. infestation has been mainly in the Southeast. In Georgia during the 1980s, wheat crop losses totaled $28 million in one year when the insect overcame the plant's resistant gene that was being used at the time.

Over the past two years, the pest also has caused extensive yield losses i
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Source:Purdue University