Effects of Varying Twospotted Spider Mite Infestation Levels on Strawberry Yield1

Publisher Website
Google Scholar
Abstract
Varying infestation levels of Tetranychus urticae Koch were created on strawberry plants by application of cyhexatin at density treatment levels of 0–5, 25, 50, 75, and 100 mites/leaflet, and subsequent yield responses were determined. Seasonal accumulations of 15597, 6261, and 6768 mite-days/leaflet in the untreated controls in 1976, 1977, and 1978, respectively, significantly reduced yield in comparison with cyhexatin treated plots. No yield differences occurred between plots treated at 25, 50, 75, and 100 mites/leaflet, although seasonal mite infestation levels ranged from 781 to 3631 mite-days/leaflet and from 1 to 4 cyhexatin applications were required. Four to 7 cyhexatin applications were necessary to maintain mite infestation below the 0–5 mites/leaflet level, and in 1977, these plots yielded significantly less than plots with higher mite treatment levels. Thus, an acaricide application at a density treatment level of 50 mites/leaflet would provide effective T. urticae control on summer planted strawberries in southern California. Predatory arthropods did not regulate mite populations in these studies. Seven predators were present with predominant species being the sixspotted thrips, Scolothrips sexmaculatus (Pergande), in 1976 and 1977 and a cecidomyiid, Arthrocnodax occidentalis Felt in 1978.