Stink bugs are best known for their stench when squashed. However, the insect is gaining more notoriety in the Midwest for another reason — their love of soybeans.
The insect has been in the Midwest for years but became more prevalent with the invasive brown marmorated species, says Andy Michel, entomology professor at Ohio State University (OSU). The bug sounded alarms when it began feeding on a row crop.
“Stink bugs love soybeans,” he says. “They use their piercing, sucking mouthparts to go straight for the pod of a developing seed. Imagine a straw sucking water from a glass.”
The result, according to Michel, can trick some producers into thinking their fields are not infected and by the time they realize they need to do some pest control it’s already too late. This is a good reason to call pest control professionals every so often as a preventative measure.
“Sometimes you have a shriveled, wrinkled seed. Other times, it’s a discolored seed,” he says. “We’ve also seen pictures from a grower who had no idea there was any damage because the pod retained its shape as if a full seed was in there. Then you open the pod to find it’s all gone.”
While stink bugs are small, their mouthparts are mighty. According to Michel, there have been accounts in Ohio of 10% to 20% yield loss in a single field bordering a forest — stink bugs’ preferred breeding ground.
Though OSU cannot yet prove why stink bugs prefer soybeans over corn, Michel does have a hypothesis that connects bug hatching seasons to soybean’s early reproductive stages in July, when pods are bright green and more of an “attractive” food source.
Stop the Stink (Bug)
If a grower suspects a stink bug infestation, a quick net pass will provide economic threshold feedback.
“Using sweep nets, do a set of 10 sweeps. If you find four or more stink bugs — doesn’t matter the species or life stage — that’s your economic threshold,” Michel says.
Before spraying, create a pest control plan. Most stink bugs prefer the outer rows along tree lines, but they can make their way to the interior of the field. With this in mind, Michel suggests:
1. A thorough scan of the field.
2. Mulling over sprayer boom options.
“I know of growers who used a 50′ boom to spray just the edges, and that really helped,” he says. “You might fight the bordering tree branches, but, with rising input costs, it’s better than spraying the entire field.”
The Good Stink
A fun fact, Michel says, is not all stink bugs are foes. “The spined soldier and two-spotted stink bugs are predators,” he says. “They will feed on pest stink bugs, caterpillars and other kinds of larvae in soybeans.”
The predative stink bugs’ role in biological control and overall help in the field make them worthy of celebrity status, according to Michel.
“When scouting for any invasive insect, it’s critical to know what you’re actually looking for,” he says. “As it turns out, these are the ‘good’ stink bugs worth knowing.”