What is in this article?:
- Kudzu bug infestation in Alabama soybeans a preview of whatâ€™s to come
- Other soybean insect pests can cause problems
- Lesser cornstalk borer
- Kudzu bugs were attacking early season soybeans in Alabama in late June.
- The insect pests traveled directly from overwintering sites to young soybeans.
- Immature kudzu bugs can be mistaken for aphids.
SOME SOYBEAN producers in Alabama were seeing kudzu bugs in almost plague proportions in late June.
Other soybean insect pests can cause problems
There are several insect pests of soybeans other than kudzu bugs that growers should be concerned about this year, notes Reed.
“Cutworms will feed on soybeans, cotton and corn. They’ll cut off the plants at ground level and sometimes they’ll chew on the leaves. Their damage might be mistaken for hail damage, and they can hurt a stand severely.”
Cutworms feed on existing winter vegetation until it deteriorates, he says. If they’re feeding on a nearby pasture or on weeds and you don’t spray a pyrethroid, you might lose a stand due to this pest, says Reed, so they need to be controlled at planting time.
“Thrips also can get on soybeans and slow them up. They can especially slow the recovery of soybeans whenever the crop has been burned by herbicide applications.”
Three-cornered alfalfa hoppers also are becoming more of a widespread pest on soybeans, he says. Adults overwinter and lay eggs inside the plant, so the eggs are hard to find. “In the immature stage, there’s nothing else that looks like it. They’ll girdle the main stem whenever you have very small beans.
“This pest is pretty abundant in the field until soybeans are about knee-high. Since we don’t have good thresholds for three-cornered alfalfa hoppers on seedling soybeans, when consultants pick up three or four on 10 sweeps on small beans, they’re going ahead and making applications. We haven’t had problems yet with secondary pests coming behind these applications. Kudzu bugs may mean that this will no longer be an issue, since we have them at the same time of the season.”
As a general rule, three-cornered alfalfa hoppers tend to be more severe in beans planted behind wheat, and in Alabama, most soybeans are planted behind wheat, says Reed.
“They tend to be higher up on the plant and can be caught with a sweep net. You’ll have to use a drop cloth to catch the immature ones. Significant yield losses are most likely when you have a lot of girdling and the plants are small. Once the plants are setting pods, the amount of yield loss you’ll have from one per sweep is not that heavy.”