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Black caterpillar feeding on green soybean leaf.

Start Scouting Fields for Thistle Caterpillar Activity

Many of our summer insect pests overwinter in the Southern U.S. and rely on wind currents to travel north in the spring and summer. The thistle caterpillar is one of those pests.

Green sunflower leaves with two snails present on them.

Snails Observed in South Dakota Sunflower

Last week we received reports of snail populations causing issues in South Dakota sunflower fields. Snails are normally not an issue in South Dakota crops but like their slug relatives, they can pose a threat to crops when field conditions are just right.

Two caterpillars feeding on soybeans. Top: Green cloverworm caterpillar. Bottom: Alfalfa caterpillar.

Soybean Defoliators Are Active

It’s that time of the season when numerous defoliating insects can be observed in a single soybean field. Most of the defoliators at this time are green cloverworms and alfalfa caterpillars.

Top: Tan caterpillar with dark brown head on corn stalk. Bottom: Black caterpillar with light stripes and yellow-brown head capsule. Caterpillar also has small spines on body segments.

Caterpillars Active in South Dakota Corn Fields

Both European corn borer (Ostrinia nubilalis) and corn earworm (Helicoverpa zea) are active in corn fields. Sometimes the caterpillar activity and identity of these two species can be confused.

Left: Bird cherry oat aphids. Right: English grain aphids.

Aphid Populations Are Starting to Show up in Corn

Small populations of aphids are starting to show up in corn fields, which could be problematic if the populations continue to grow. During dry seasons, they can have a greater impact on corn.

Green leaf with two yellow spider mites with dark spots.

Dry Conditions Are Ideal for Spider Mite Activity

Several counties in South Dakota are experiencing dryer than normal conditions, therefore, it is important to monitor crops for spider mites, as they thrive during periods of dry weather.

A pasture containing a mixture of grasses and alfalfa.

Start Scouting for Grasshopper Activity in Crops and Grasslands

Most of Eastern South Dakota is experiencing very low grasshopper populations. However, this is not the case for many areas in Central and Western South Dakota.

Three corn diseases. From left: Southern Rust, Bacterial Leaf Streak, and Eyespot.

Southern Rust, Bacterial Leaf Streak, and Eyespot Are Developing in Corn

Southern rust was found in Yankton County, bacterial leaf streak was found in Brule County, and eyespot was found in several fields and counties the week of July 27, 2020.

Small white insects with tent like wings present on a green leaf.

What Are These Small White Insects in My Soybean Field?

During the last two weeks we have received reports of increasing numbers of small white insects present on soybean. The insects in question are whiteflies.

Small reddish-orange beetles on a green sunflower bud with a larger grey beetle also present.

Identifying Red and Gray Sunflower Seed Weevils

When scouting sunflower, the most observed weevil is the red sunflower seed weevil. However, there are two species of seed weevils that can be present on sunflower heads in South Dakota.