What is in this article?:
- 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.
Lesser cornstalk borer
Lesser cornstalk borer can be a problem on soybeans in dry weather, he says.
“They’ll bore into young stems, burrow up and down the stems, and kill the plant. You can determine if these are in your field with pheromone traps.”
Damage also has been seen in soybeans from pillbugs that feed on the leaves and destroy the stand, says Reed. “We have not had a problem controlling these with pyrethroids. You may see them in large numbers in beans planted behind wheat. They feed on the plants at night and go down during the day.”
A 10-percent stand loss is a good general rule to follow on soybean seedling pests, he says.
Growers should look for podworms to start showing up on soybeans when the plants start to bloom, says Reed.
“They’re typically high on the plants in the morning, moving down on the plant as the temperature warms. Most research shows that with $8 beans, the threshold ranges from 1.7 to 2.5 per row foot. The plants can compensate early when the beans are small but less so later in the season. We use a conservative threshold of one per row foot in Alabama. You can control these insect pests with a pyrethroid. The threshold is about three per 15 sweeps.”
Once a stink bug matures, it could be in your soybean crop for up to two months, he says. “Soybeans are susceptible to stink bug damage up to maturity. This insect will slowly increase in Alabama, and eventually it will be a major pest on soybeans, cotton and corn.
Soybean loopers are serious defoliators of soybeans, feeding on foliage and most often being a pest from late August through September.
Fall armyworms also can feed on soybean pods, says Reed.
“Remember when we’re dealing with double-cropped soybeans behind wheat that you’ll probably be dealing with complexes of insect pests. You may have sub-thresholds of several different insect pests, including stink bugs, three-cornered alfalfa hoppers, kudzu bugs and worms. A lot of farmers are cleaning up their soybeans in the early pod-fill stage, when they’re putting out their fungicides.”
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