Spider Mite Control in Vineyards

Three trials were conducted to evaluate the utility of oil sprays and other OMRI approved products as integrated controls of spider mites, leafhoppers and powdery mildew. The results of one trial in Tracy, CA show that JMS Organic Stylet Oil and to a lesser extent Trilogy, applied for powdery mildew control, significantly suppress leafhoppers and mites on grapevines. These two products also performed equal (Trilogy) or superior (Stylet Oil) to micronized sulfur as a powdery mildew treatment. No treatment effects on Brix or berry weight were detected. Also, it appeared that when Stylet Oil applications ceased at the end of June, leafhopper and mite populations remained suppressed until August. Stylet Oil season-long treatment in table grapes may not be acceptable due to the substantial effect on the berry bloom appearance. For table grape production ceasing Stylet Oil sprays at veraison will allow ample time for berries to regain their waxy bloom by harvest for mid to late harvest grapes. At a second location (Courtland, CA) spider mite densities were extremely low, however predator mites, which were abundant at this site, produced interesting observations, in that Stylet Oil (1%) did not appear to significantly affect them. A third trial (Lodi, CA) evaluated several OMRI approved miticides for the control of Pacific spider mite. Single treatments of Stylet Oil (1%and 2%), GC-Mite, and to a lesser degree M-pede appeared to suppress Pacific Mites for several weeks. Stylet Oil at 2%and GC-Mite caused substantial damage to the berry bloom, however Stylet Oil at 1%, Ecotrol EC and M-pede resulted in no bloom damage. Stylet Oil appears to be an excellent candidate alternative to sulfur for an integrated control program for mites, leafhoppers, and powdery mildew, offering superior control of all of these important pests relative to micronized sulfur. Our proposed research for 2007-08 will repeat the evaluation of season long Stylet Oil applications and its effects on mites, leafhoppers, powdery mildew, Brix, berry weight and juice pH. In addition, we will evaluate the utility of integrating several Stylet Oil (1%and 2%) sprays into a sulfur-based powdery mildew program.