Research team discovers new microbe in wheat stem sawfly

 

A team of researchers in Montana State University's College of Agriculture has discovered a previously unidentified microbe that lives symbiotically with the wheat stem sawfly, a pest that causes hundreds of millions of dollars in damage to wheat crops each year. The discovery, the result of a years-long project, provides the basis for future research that could be vital to combating losses due to wheat stem sawflies in Montana and beyond.

 

Carl Yeoman in the Department of Animal and Range Sciences and David Weaver in the Department of Land Resources and Environmental Sciences published a paper in the journal PeerJ in August along with a team of colleagues. The paper outlines the discovery of the microbe Spiroplasma sp. WSS—its name a nod to the wheat stem sawflies in which it was discovered. The project was inspired by knowledge of similar symbiotic relationships between other insects and microbes inside them.

 

Yeoman said wheat stem sawflies cause as much as $350 million in damage to wheat crops each year in the Northern Great Plains. The motivation for looking into those symbiotic relationships stemmed from a hypothesis that if the microbes in wheat stem sawflies could be identified and their functions determined, maybe they could be manipulated to work as a management tool for sawflies.

 

"Many insect species have microbial symbionts, and these relationships are often essential to the survival of both organisms," said Yeoman. "Microbial symbionts have been shown to affect everything from the reproductive success of their insect hosts to their nutrition—allowing them to survive on poor quality diets—and even their ability to defend against pathogens."

 

So, the team set out to determine what microbes are associated with wheat stem sawflies, and if they could be manipulated to affect the sawfly's ability to damage wheat crops.

 

Wheat stem sawflies are one of the more widespread wheat pests in western North America, said Weaver, damaging wheat by penetrating the stem to insert their eggs. The larvae then eat tissues lining the stem, inhibiting photosynthesis and causing lodging—weakening the stem to the point where the plant simply falls over in large swaths. The project was supported by the Montana Wheat and Barley Committee, which has long been in search of new ways to manage the pest.

 

"We've reported 20 percent to 30 percent reductions in seed weight as a result of sawfly feeding," said Weaver. "But if the stem falls and a combine doesn't pick it up, it goes from a 30 percent loss to a 100 percent loss of that stem. It's a pretty big problem, and it really frustrates growers."