No. 13 Article 5/June 17, 2005

Twospotted Spider Mites: Quick Update

As indicated in the article about soybean aphids, recent rainfall helped the soybeans in areas of Illinois, which will enable the plants to withstand infestations of twospotted spider mites, at least for a while. The cooler temperatures projected also are not conducive for rapid increase of spider mite population densities. However, a return to dryer, hotter conditions will bring back concerns about this threatening pest.

On June 7, Jeff Brown, with Monsanto Company, found a large number of spider mites in a no-till soybean field in Douglas County. Duane Frederking, with Pioneer Hi-Bred International, found spider mites in soybean in both Macon and Sangamon counties during the week of June 6. So these findings before the weekend rains suggest that twospotted spider mites were gaining footholds in areas that have suffered from a lack of moisture.

Continued surveillance of soybean fields for soybean aphids and Asian soybean rust (at least in sentinel plots) should reveal lingering or growing populations of twospotted spider mites. As we are doing for other pests, we'll keep our eyes and ears open.--Kevin Steffey

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