Tap leaves against a white piece of paper or cloth and look for moving yellow dots. Thresholds are four or more mites per leaf or one severely damaged leaf per plant prior to pod-fill. Therefore, check the short and long term weather forecasts to determine if these conditions will continue. The longer it remains hot and dry the increased likelihood that economic damage will occur from the mites. Re-scout the field a few days after a rain.
Heavy dews are often enough moisture for successful infection of the mites by parasitic fungi.
If mites are found in field margins only, do not treat the entire field, just the margins. Apply insecticides one boom length past the affected areas. If mites are throughout the field then treat the entire field. Closely monitor treated fields for reinfestation. Twospotted spider mites may damage soybeans, as well as field corn, and outbreaks typically occur during hot dry years.