Insect & Pests

All Insect & Pests Content

Three common soybean defoliating pests. From left: Green cloverworm, grasshopper nymphs, and thistle caterpillar.

Monitor Soybean for Defoliating Insects

While scouting soybean this week I noticed quite a few defoliating insects that were present in the field. So far, the feeding injury is minimal, but it is a reminder that we need to be diligent in monitoring leaves for defoliation and fields for these insect pests.

Base of soybean stem with orange larvae present under the epidermis.

How to Scout For Soybean Gall Midge

Soybean gall midge have been reported in three counties in South Dakota in the past week: Clay, Union and Lincoln. Scouting for soybean gall midge can be as simple as finding wilting or dying plants along the edge of the field, or it can be rather difficult if the plants are currently asymptomatic.

Three colored bean leaf beetles. From left: brown, red, and yellow.

Bean Leaf Beetles Are Back: Adults Observed Near Beresford

Earlier this year, we observed a large emergence of overwintering bean leaf beetles throughout much of the state. We are again observing quite a few bean leaf beetles beginning to emerge. These emerging beetles are the result of overwintering beetles mating and laying eggs.

Black and white county map of South Dakota, Minnesota, Nebraska and Iowa. Red dots within counties indicate soybean gall midge emergence. Black dots represent trap locations.

Soybean Gall Midge Are Emerging Around Us, But No Captures in S.D.

Last year, the soybean gall midge caused a lot of issues in soybean, including lodging and up to 50% yield loss. In an effort to determine when soybean gall midge adults are emerging in 2019, a network of emergence traps has been established in South Dakota, Nebraska, Iowa and Minnesota. So far, emergence of the adult soybean gall midge have been reported from Iowa, Nebraska and Minnesota.

Photo showing counties where soybean gall midge has been confirmed

Soybean Gall Midge Showing Up in More Counties

As the season continues, so is our soybean gall midge scouting efforts. For much of South Dakota, the soybean that are infested with soybean gall midge are asymptomatic. That is, they show limited signs of infestation, but we can still find the larvae of the soybean gall midge in the stems.

A young man in a gray shirt and white cap scouting a soybean field for soybean aphids.

Should I Spray for Soybean Aphids? What’s the Threshold?

Although many soybean fields are behind schedule, so are the soybean aphid populations. In many reported areas, there are hotspots within a field where a few soybean plants may be heavily infested.

A yellow beetle with a black head, and square black markings on its back standing on a soybean leaf.

2020 South Dakota Overwintering Bean Leaf Beetle Predicted Mortality

Although bean leaf beetles won’t be emerging for a while yet, it is important to be prepared for potential early season defoliation. Once soybean are planted and begin emerging, the overwintering population of bean leaf beetle adults will move into soybean fields and begin feeding on the seedlings.