A new pest is showing up in Midwest soybean fields and it’s one that researchers recommend farmers should keep an eye on. The soybean tentiform leaf miner was first found in Missouri in 2025 but has now been confirmed in seven states, including Wisconsin, which reported detections in 2026. University of Missouri extension entomologist Ivair Valmarbida says it could be in more fields than current monitoring has found to date.

The caterpillar feeds inside the leaf, so it is easy to miss, and the blotchy areas it creates can lead to defoliation. Most detections came from July through September, mainly along field edges near trees and wooded areas. Infestations in Missouri have been light and below economic thresholds, but the yield impact is still unknown, and research is ongoing. For Missouri farmers, the recommended defoliation thresholds are 30% before bloom and 20% after bloom, and finding the pest does not automatically mean a spray is needed. Valmarbida noted that more research and field monitoring are ongoing as they learn more about the impacts on soybean production.

Read more commentary from AgWeb and an in-depth overview of the pest from Valmarbida.