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Scientists use 'insect perfumes' to lure stink bugs to expendable crops

March 15, 2016

Mating harlequin bugs
Mating harlequin bugs. Courtesy of Tom Kuhar.

When a stink bug finds a plant to eat, it produces a pheromone that alerts other stink bugs to the food source, similar to the ringing of a dinner bell.

A team of Virginia Tech researchers is studying the biosynthesis of this pheromone in order to mimic it and attract the pests to expendable food plants—also called ‘trap crops’—rather than cash crops.

With funding from the USDA, researchers Dorothea Tholl and Tom Kuhar in collaboration with colleagues at the USDA ARS in Beltsville, Maryland, are just beginning the four-year project that they hope will save farmers millions of dollars.

“By understanding the biosynthesis of these volatile pheromones in stink bugs, we will be able to assemble gene tools to cost-effectively produce these chemicals, via synthetic biology, for their application in the field to trap stink bugs,” said Dorothea Tholl, an associate professor of biological sciences in the College of Science and a Fralin Life Science Institute affiliate. “In addition, we plan to design chemically-modified trap crops that directly release the pheromones to attract and re-route the bugs away from commercial crops.”

In Virginia, crops like sweet corn, wine, grapes, and apples have been under attack by the invasive brown marmorated stink bug since 2004 and cabbage has been affected by its similarly stinky cousin, the harlequin bug.

If successful, the genetic engineering technique would be an environmentally friendly alternative to using insecticides.

“Currently, most growers combat these difficult pests with applications of broad-spectrum insecticides,” said Kuhar, a professor of entomology in the College of Agriculture and Life Sciences and a Virginia Cooperative Extension specialist. “These insecticide applications have been shown to have negative non-target impacts on natural enemy populations and pollinators and alternative strategies for stink bug management are badly needed.”

 

Lancaster examines harlequin bug infestation
Doctoral student Jason Lancaster examines a harlequin bug infestation on collars at Kentland Farm last August. Photo courtesy of Tony Dimeglio.

Jason Lancaster of Knoxville, Tennessee, a biological sciences doctoral candidate working with Tholl, recently used next-generation sequencing to identify the first enzymatic step in the biosynthetic pathway of the harlequin bug pheromone compound.

“Our work targets the production of the bug’s pheromone and not its defense compound (the stink),” said Lancaster.  “The enzyme I’m studying is only one step in the biosynthetic pathway but has already provided some very valuable information.”

So far, Lancaster has determined that the harlequin bug makes the pheromone on its own, without using microbes or the host plant.  Meanwhile, early work on the brown marmorated stink bug suggests it has a very similar enzyme to the harlequin bug and both differ significantly from other insect enzymes of this type.

“This divergence, along with the similarity between stink bug pheromones, suggests an evolutionary event that led directly to a unique pheromone biochemistry,” said Lancaster. “We assume that similar events have occurred in other insects allowing exciting future discoveries in the biosynthesis of pheromones and their application.”

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