Tuesday, September 21, 2010

Virginia Peanuts: Spider Mite Infestations Picking Up

From Ames Herbert, Virginia Tech Extension Entomologist

It is not surprising that we are getting reports of spider mite build-ups in peanut fields. There are areas that have been fighting this dry weather pest for several weeks. These newer outbreaks are particularly bothersome as they are coming so close to the end of the season. 

D. Rick Brandenburg (NCSU) and I have done a lot of work on how to achieve the best control of spider mites in peanuts. There are several limiting factors, not the least of which is the limited number of products registered for spider mite control in peanut. There are only three products currently labeled, Danitol, Brigade and Comite. 

For reasons that must have to do with marketing, Comite has not been readily available to Virginia growers for the last 3 or 4 years. That leaves Danitol and Brigade (= Capture) which are both pyrethroids. These products if applied with high spray volume (15 + gpa) will provide good knockdown of adult and immature mites. But, neither kills the eggs so if applications are made to fields where there are a lot of eggs, these hatch in 2 or 3 days and the infestation begins again. 

Our work showed that the only way to make these products work well was to make two sequential applications about 5 to 7 days apart. The first application knocks down the adults and immatures, and the second gets the new hatchlings, thus breaking the cycle. 

But, this late in the season when digging will begin soon, we are recommending that if mites are doing a lot of damage and need to be controlled, make a single application using the highest labeled rate, knock them back, and hope for the best.

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