Microbe discovery may control sawfly

Recent research to control sawfly has made progress that could ultimately help reduce the pest’s damaging impacts.

Researchers at the Montana State University’s College of Agriculture have discovered a previously unidentified microbe named Spiroplasma sp. WSS that lives symbiotically with the sawfly. That may be the “in” researchers were looking for to help with future control measures.

Carl Yeoman, associate professor at the university’s department of animal and range sciences, said while a lot of work is needed to evaluate and field test methods for exploiting the relationship between the sawfly and the microbe, it shows promise.

“Nevertheless, the ultimate success of this research endeavor will be a solution to the more than $350 million in damage wheat stem sawflies do to wheat crops in the northern Great Plains annually and money back in the pockets of our wheat farmers.”

Wheat stem sawflies damage wheat by penetrating the stem to lay their eggs. The larvae eat the tissue lining the stem, which interferes with photosynthesis and weakens the plant to the point where it falls over.

Many insects have microbial symbionts essential to their survival or reproductive success. Wheat stem sawflies depend on the microbe to help break down sugars and create other nutrients they do not get from their heavy carbohydrate diet.

By better understanding the microbes’ role, researchers hope they can manipulate it as a management tool to interfere with the sawfly’s survival.

“Based on the genomic information we have available for both (microbe and wheat stem sawfly), there is evidence that the microbe contributes to the nutrition of the insect, including providing key B vitamins that aren’t available within its diet. Our next steps are to test this experimentally and also evaluate other potential interactions between the insect and the bacterial species.”

Yeoman said the next focus of the research will be to find cost-effective and environmentally and consumer-acceptable strategies that disrupt the relationship between the insect and the microbe and are effective at controlling the pest.

One approach is to focus on the insect’s larvae with the use of antibiotics.

“Work from our collaborator Dr. David Weaver has already shown that eliminating the microbe with antibiotics leads to the death of the sawfly,” said Yeoman. “The problem, however, is that the large-scale application of antibiotics to agricultural lands that would be necessary to control the wheat stem sawfly populations would not be environmentally responsible, nor consumer acceptable.”

Weaver, who works with the department of land resources and environmental sciences at MSU, said in a news release that a group of scholars working in China examined a similar system in pea aphids and found that when symbiotic microbes were inhibited with the use of antibiotics, the fertility of the aphids fell significantly, reducing their population and risk posed to pea plants. In another case, scorpion venom was used.

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