Effect of Pesticide Interactions on the Twospotted Spider Mite on Peanuts^1,2

Pesticides commonly applied to the foliage of peanuts in North Carolina were evaluated under field conditions for their effect on the twospotted spider mite Tetranychus urticae Koch. Most fungicides caused a higher mite increase than insecticides on NC 2 peanuts. When fungicides and insecticides were tank mixed or applied on alternate weeks, mite outbreaks occurred. These outbreaks were followed by severe injury to the foliage and finally defoliation and yield reductions.

Among the fungicides applied only Du-Ter and Copper Count failed to cause significant mite damage even when combined with an insecticide. Since mites failed to develop on untreated peanuts following six or more mite releases during the season, it was apparent that pesticides predispose peanuts to spider mite buildup and damage.