Spider Mite Control in Vineyards (Year 2).
Efficacy of the conventional acaricides abamectin (Agri-mek), etoxazole (Zeal), fenpyroximate (Fujimite), spirodiclofen (Envidor), acequinocyl (Kanemite), bifenazate (Acramite), hexythiazon (Onager), propargite, and horticultural mineral oil were evaluated for their effect in controlling a mixed population of Pacific spider mite and Willamette spider mite in an El Dorado Co. merlot vineyard during summer, 2007. All acaricides significantly reduced mite densities relative to the untreated control for all but one sampling date for 4 weeks following the application. During the course of the experiment, the Willamette spider mite was the dominant species present. We monitored a number of vineyards in the northern San Joaquin Valley and Napa Co. throughout the summer and were unsuccessful in our attempt to locate a treatable population of Pacific spider mite. We also evaluated efficacy of organic acaricides in a separate experiment in the El Dorado Co. vineyard. Treatments included Organic JMS Stylet Oil, GC-Mite, Ecotrol, Organocide, and M-pede. The mean motile spider mites in all of the organic treatments were significantly lower than the mean density of the untreated control plots (P < 0.05) for 3 weeks following their application with the exception of M-pede on August 22. We completed a life table evaluation of the effects of newer acaricides on Pacific spider mite. At chemical concentrations equivalent to the high label rate of each product, only females exposed to Zeal, Envidor, Nexter and Agri-mek had any amount of survival as measured by longevity of females, and survival in all treatments was significantly (P<0.05) lower than observed in the control treatment. None of the females surviving except for those exposed to Zeal produced eggs, and all of those eggs were sterile. Reduced concentrations resulting in mortality of 20%of the Pacific mites treated with each acaricide clearly revealed mechanisms for the activity of these products.