University of Illinois

No. 18/July 25, 1997

Update on Spider Mites

Our phones aren't ringing off the hooks yet, but many folks are still wary of spider mites in soybeans. The memory of 1988 has not faded. However, although we continue to hear about problems with spider mites, primarily in northern counties, we do not seem to be experiencing an outbreak. Nevertheless, these rapidly reproducing pests bear watching. Robert Bellm, Extension crop systems educator in Edwardsville, indicated that spider mite problems were beginning to crop up (pardon the pun) in southern counties.

Recent rains should alleviate some of our concerns. However, some people mistakenly believe the rain itself kills the mites. Although I imagine a hard, beating rain accompanied by roaring winds would aggravate any proud spider mite, I believe that most of the mitigating effects of rainfall are indirect, as explained in last week's issue (no. 17, July 18) of this Bulletin. Let's keep hoping for rain for many reasons, but especially to boost soybean plants' ability to withstand the spider mites. Also remember that humid weather could bring about an epizootic of a pathogenic fungus that can "crash" a population of spider mites in a matter of days.

I have heard nothing more about difficulties in controlling spider mites with either dimethoate or Lorsban. However, if you have any experiences to share, don't hesitate to contact us. If control problems arise, everyone will want to hear about them.

Kevin Steffey, Extension Entomology, (217)333-6652