A spider mite-resistant and a spider mite-susceptible variety of cotton were planted in the field in a replicated design. An acaricide (dicofol) and an insecticide (acephate) were used to manipulate numbers of spider mites and their natural enemies. In general, numbers of spider mites remained low until just before midseason when 650 °D air temperature had accumulated. At 650 °D, mite numbers began to increase more sharply and reached significantly (P<0.001) greater levels on susceptible plants than on resistant plants. Although natural enemies, such as Geocoris pallens Stål, Orius tristicolor (White), and Frankliniella occidentalis (Pergande), were slightly more apparent on susceptible plants than on resistant plants, these differences were not statistically significant, and cotton varietal resistance was compatible with biological control.
