Engineering a new kind of pest control

Researcher efforts would corral stink bug damage
The brown marmorated stink bug is a pest in farmers' fields and orchards as well as in the home.   Rich Cooley/Daily

The brown marmorated stink bug is a pest in farmers' fields and orchards as well as in the home. Rich Cooley/Daily

As the winter cold gives way to spring, the pesky brown marmorated stink bug population will start crawling from refuge in attics and buildings to lay eggs and wreak havoc on crops later in the season.

But solutions to the harmful infestation of these invasive bugs might soon be visible on the horizon – if you squint a little bit. Researchers from Virginia Tech and the U.S. Department of Agriculture are exploring options for minimizing the bug’s damage to crops.

Dr. Deborah Tholl, associate professor of biological sciences at Tech, said the collaborative team is looking to put an engineering twist on the practiced use of “trap crops” to draw the bugs away from some of their favorite snacks like apples, peaches and soybeans. The pests – native to eastern Asia – have ruined produce for market since their spread into the region around five years ago.

Tholl said traps and trap crops are an alternative to blasting broad-spectrum insecticides that harm beneficial and native insects. The stink bugs release certain pheromones that attract other bugs to a food source. Using the “attract and kill” method with those pheromones on trap plants can target the edges of cropland near forests, where the bugs tend to cause the most damage.

But those pheromones can be expensive, especially when needed for multiple applications. Tholl said the engineered plants would continuously release the chemicals and attract the pests.

“We basically would take what we know in terms of how these compounds are made in the insect … and then metabolically or genetically engineer these trap crops,” she said. “They’re dispensable, they can be recommended at any time for the field.”

Tony Dimeglio, an entomology graduate student at Tech, said that researchers will be focusing efforts on the mustard plant, which is used to attract other stink bugs. He’s fine-tuning a combination of pheromones, scents and colors to form the most effective trapping device for harlequin bugs, which produce similar chemicals to ones the brown marmorated stink bugs release.

“This is when the bugs are waking up. If you have the pheromone on a trap crop like a mustard crop … you capture those ones that are spread around the farm and then you can kind of take out the initial population,” he said.

While Tholl said the interdisciplinary research is an exciting opportunity for the team, engineering the trap crop will take some years and recommendations for its widespread use would come further in the future.

“We have a four-year grant on this from the USDA … we believe that we can be in the stage of engineering these plants at the end of that time,” she said.

Dr. Christopher Bergh at the Alson H. Smith Jr. Agricultural Research and Extension Center in Winchester said there’s another, broader solution for controlling the stink bug population – which comes in the form of a tiny insect parasite.

Bergh said USDA researchers had worked with the Trissolcus japonicus wasp under quarantine to judge whether or not it would be safe to introduce it into the wild. But the species was found in the wild elsewhere in the mid-Atlantic region, meaning that it had already migrated from Asia to the U.S. some other way. Researchers on the West Coast even found evidence of the wasp.

The wasp is a parasitoid that attacks brown marmorated stink bug eggs – one of the bug’s few natural enemies. Bergh said he set up sentinel stink bug eggs in various locations last summer and encountered the wasp around Winchester. From this summer onward, he said he’ll be on the lookout to monitor and study the eggs and wasps.

“In 2015, the bug population was rather low compared with some previous seasons … we started off the year with a much smaller population than we do in other years,” he said. “This year we had a much milder winter … and we feel that it’s likely that many more of the bugs survived this winter than they did last winter.”

Bergh said USDA work with the wasps revealed that there’s a chance they might prey on native stink bugs’ eggs as well, which is a serious consideration for releasing those wasps. Other than that, he said there’s little risk to humans, plants or other native species.

“I think it’s likely that the benefits of brown marmorated stink bug suppression by the activity of this parasite will far outweigh any probably relatively small negative impacts on any native stinkbug species,” Bergh said. “I think we all hope that each year we’ll see more evidence of this Asian parasite and we’ll see more evidence of its impact.

“Biological control of the brown marmorated stink bug may be the ultimate solution,” he said.

Learn more about the brown marmorated stink bug and managing efforts at http://www.stopbmsb.org/.

Related: Growers vs. stink bugs: learning effective chemical use

Contact staff writer Rachel Mahoney at 540-465-5137 ext. 164, or rmahoney@nvdaily.com

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