By Laura Temple, adapted from Soybean Research and Information Network, November 7, 2022
Multiple stink bug species can infest soybean fields. Brown marmorated stink bug, an invasive species currently moving across Ohio, is the primary problem species there, according to Kelley Tilmon, professor of entomology at Ohio State University. However, green stink bugs, brown stink bugs and other species also damage soybeans.
“Stink bugs feed on developing seeds,” she explains. “They punch through pods with their sharp, straw-like mouth parts. Then they secrete digestive chemicals that allow them to slurp up developing seeds.”
Tilmon adds that when stinkbugs feed later in the season, they cause soybeans to shrink, reducing their quality. When they feed early in reproductive growth stages, pods may not produce any soybeans.
“Stink bugs can cause yield losses of up to 20 bushels per acre if not controlled,” she says. “The good news is that stink bugs are very easy to control with insecticide. The bad news is that farmers seldom know they have a problem until harvest.”
In soybeans, entomologists recommend scouting for stink bugs with a sweep net. However, the pests feed on soybeans as pods fill, when the plants are at peak density. Soybeans have branched out to fill in all the space between rows. In Ohio, that’s usually in August and early September.
“It is physically hard to walk through soybeans at that time of year, so stink bugs often go undetected,” Tilmon says.
Adapting Orchard Technology
While waiting her turn to present at a pesticide applicator training a few years ago, Tilmon listened to a fruit and vegetable entomologist discuss monitoring and managing stink bugs.
“I learned that in orchards, pheromone lures and sticky traps are used to monitor stink bugs,” she says. “I wondered if that technology could be adapted for row crops.”
She brought the idea to the Ohio Soybean Council, and the board invested checkoff funds in her research to develop a new method for scouting stink bugs in soybeans. Her study will develop recommended treatment thresholds that correspond with this monitoring system.
Tilmon started with the most commonly used brand of commercial pheromones used to monitor stink bugs in orchards. Her team has evaluated the efficacy of the pheromone in drawing stink bugs to the trap — a clear sticky card mounted on a post by the field edge. They have also been working to establish the relationship between captured stink bugs and in-field populations. Next steps will include evaluating different brands of pheromones to determine which attracts the most species.
“Stink bug populations vary between fields,” she explains. “Some fields have a predominant species, while others have a very mixed stink bug profile. Based on my years of observations, I think the type of shelter available around a field for overwintering contributes to the types of stink bugs found in that field. For example, some species may prefer to overwinter near specific types of trees or vegetation in woods, in shelter belts or around outbuildings.”
During the first year of the study, Tilmon and her team experimented to determine the most effective spacing between posts holding the sticky traps with pheromones along the edge of fields. Over the 2021 and 2022 growing seasons, they worked to develop correlations between stink bugs caught on the edge of the field and the actual infestation levels in fields.
“We monitored traps on the edge of fields and then used sweep nets in the fields,” Tilmon says. “We need lots of data from a wide variety of fields to develop reliable correlations for specific species and the entire stink bug complex.”
If measurements are consistent, she says two years of data is sufficient to make correlations. As of the fall of 2022, she believes her team is closing in on recommendations for Ohio. Those recommendations will include trap placement, frequency of checking traps and threshold information to help farmers decide when to take action.
The stink bug thresholds developed from this scouting method will vary depending on the end use of soybeans. Tilmon says the threshold set for grain soybeans will be higher than the thresholds used for seed soybeans and food-grade soybeans because of their quality requirements and the type of damage stink bugs cause.
Multiplying Checkoff Investment
After demonstrating the potential to improve stink bug monitoring, Tilmon’s concept was picked up by the North Central Soybean Research Program. With this additional soy checkoff support, her protocol was made available to other states.
She notes that every state needs to verify data and set thresholds specific to their stink bug species, crop maturity timing and other factors. However, those states can build on her team’s work.
Tilmon believes this project exemplifies efficient use of soy checkoff investments in research.
“The concept came from a different agricultural system,” she explains. “Ohio took the lead on doing the legwork to adapt the technology for soybeans. Checkoff funding through NCSRP is allowing more states and farmers to benefit from these investments.”
Additional SRIN Resources: https://soybeanresearchinfo.com/?s=stink+bugs