The invasive brown marmorated stink bug (Halyomorpha halys) “will eat almost anything” and “attacks more than 170 different plant species,” according to StopBMSB.org. Among those targets is soybean, the number-two crop in the United States. Researchers at the U.S. Department of Agriculture’s Agricultural Research Service are working to identify soybean breeds that exhibit resistance to the pest. (Photo credit: Christopher Nacci, USDA-ARS)

It’s been two decades since the invasive brown marmorated stink bug (Halyomorpha halys) arrived in the United States, first in Pennsylvania. In the time since, it has reached at least 42 other states, threatening a wide range of crops including corn, apples, grapes, and soybeans, just to name a few.

Though the pest has generally eluded many efforts to manage it, researchers across the U.S. are exploring a multitude of possible new management methods or improvements to existing ones. One of those possibilities lies in developing crops that are resistant to the brown marmorated stink bug’s damage. In a study published last week in the Journal of Economic Entomology, researchers at the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS) report on their search for host-plant resistance in soybean, a potential boon to integrated pest management programs for the brown marmorated stink bug (BMSB).

To begin, a team led by Jonathan LaMantia, Ph.D., a research molecular biologist with the USDA-ARS Corn, Soybean and Wheat Quality Research Unit in Wooster, Ohio, tested more than 100 different soybean lines from the USDA’s soybean germplasm collection, a repository for genetically diverse breeds of the crop. They infested the soybean lines with brown marmorated stink bug during pod development to identify which ones showed signs of resistance to BMSB feeding, followed by repeat testing on the four most resistant and four most susceptible lines.

In each of the experiments, two lines—known as PI (plant introduction) 097139 and PI 085665—had the fewest number of pods with BMSB feeding damage. They also found that, in the susceptible lines, older pods had less feeding damage than younger pods.

The latter finding may be of more immediate use to growers, says LaMantia, but the former will guide further research and development of BMSB-resistant soybean.

“Our findings indicate soybeans pods are less susceptible once plants reach the R6 growth stage. Thus, farmers may not need to apply insecticides past the R6 pod-fill stage to control for BMSB,” LaMantia says. “Further in the future, we can use the two PIs to identify genetic markers associated with BMSB resistance and incorporate the resistance traits into soybean cultivars.”

Perhaps not coincidentally, soybean PIs 097139 and 085665 originate from Japan and North Korea, where BMSB is native.

“In general, when a host and a pest’s native ranges overlap there is the potential for co-evolution. The pest selects for resistance within the host population then the resistant host selects for new virulence in the pest population,” says LaMantia. “When we initiated the project, we were hopeful that a source of resistance could be found in the soybean germplasm repository.”

In area, soybean is second only to corn among row crops in the United States, so protecting it from BMSB is a high priority. LaMantia says USDA-ARS is screening additional soybean lines for resistance and next summer will continue tests on PIs 097139 and 085665 to narrow down the genetic source of their resistance to brown marmorated stink bug damage.