Twospotted spider mites have been spotted in fields across much of Iowa already this summer, as much of Iowa is in moderate or severe drought (D1-D2, US Drought Monitor). I encourage you to scout for twospotted spider mites in crops. Twospotted spider mites can increase whenever temperatures are greater than 85°F, humidity is less than 90 percent, and moisture levels are low.
While some rainfall has come to the droughty areas of the state, drought intensified to D3 (extreme) drought in parts of central and west central Iowa. Unfortunately, a large swath of the state is now facing devastating infrastructure and crop damage after the August 10 Midwest Derecho. Our thoughts are with all Iowans as they work to assess and recover from damage.
Observations across several counties in southeast and south central Iowa show that, despite some recent rain events and high humidity, twospotted spider mites are persisting in both corn and soybean fields across the area. These insect-like pests can be very difficult to identify, so we’ve got a few points below to help you find them.
A few places in Iowa and surrounding states have reported heavy twospotted spider mite populations in soybeans, and the first reports of spider mites in Iowa corn started this week.
Crop consultants in southwest Iowa have reported finding twospotted spider mites this week. Scouting for initial infestations is important to avoid yield loss. Foliar insecticide treatments should be made to fields before prolonged spider mite feeding causes yellowing or leaf drop
