Insect & Pests

Economically Damaging Soybean Aphid Populations Detected

Soybean aphid populations continue to grow in South Dakota. This week, counts near Volga ranged from approximately 280-700 aphids per plant. Observations of these populations indicate that they are healthy and will continue to increase.

Scout Soybean in Drought-Affected Fields for Twospotted Spider Mites

One of the pests that typically shows up during drought conditions is the twospotted spider mite (Tetranychus urticae). Infestations of this pest were recently confirmed in Eastern South Dakota soybean and corn.

Sunflower Pest Recap

During 2026, we will be producing a new weekly update on sunflower insect pest activity. This information will be attained via a sampling network of eight locations that are in central South Dakota.

Japanese Beetles in South Dakota

In the last 10 years, Japanese beetle populations have remained low to absent in my garden in Brookings. However, last week I observed large aggregations of beetles feeding on smartweed that was present in my rain garden. Japanese beetles can be problematic for gardens, flowers, and trees in residential areas.

Several Species of Caterpillars Are Actively Defoliating Soybean

There are several species of caterpillars that have recently been observed in a single soybean field. The species include the green cloverworm, cabbage looper, alfalfa, thistle, and oblique banded leaf roller caterpillars.

West Nile Virus Update: July 29, 2026

As of July 30, 2026, the South Dakota Department of Health indicated that West Nile Virus positive mosquito pools have been detected in Brown, Codington, Hughes, Lincoln, and Minnehaha counties in South Dakota.

Aphid Populations Observed in South Dakota Corn Fields

During the last week, we have observed low level aphid populations in corn fields. Although aphid populations can reach high densities in corn, their presence doesn’t indicate guaranteed yield loss.

Soybean Aphid Populations Have Reached Economic Threshold

Based on recently scouting observations, the economic threshold for soybean aphids has been reached. Once thresholds are reached, fields should be reevaluated in 3 to 4 days to confirm the populations didn’t decrease, and if they persist or increase, they should be treated.