Content by Adam Varenhorst

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.

It’s Time To Scout for Soybean Aphids

While scouting soybeans last week, we observed small populations of soybean aphids. These populations suggest that the infestation was recent. In 2025, we observed similar small infestations that took a long time to increase.

Monitor Your Corn for Corn Rootworm Adults to Inform Management for Next Year and to Avoid Substantial Silk Feeding

Corn rootworm adults are active across South Dakota, and as a reminder, it’s a good time to scout to determine if your fields have a rootworm issue.

Start Scouting Your Sunflower Fields for Red Sunflower Seed Weevil Presence

Red sunflower seed weevil adults have been detected in South Dakota. Current recommendations for management in both confection and oilseed sunflower is to begin treatment when the majority of the field has reached the R5.4 growth stage, but applications done between R5.1 and R5.4 can still provide yield protection.

To Avoid Loss of Viable Seeds This Year, Keep an Eye Out for Banded Sunflower Moths in Sunflower

Banded sunflower moths are active in South Dakota, which means it is time to start scouting sunflowers for their eggs. The caterpillars of banded sunflower moths are capable of reducing yields and oil content by feeding on the developing florets and tunneling into developing seeds.