Effect of pesticides and three sulfur-based products on integrated mite management in Washington State

Luis Martinez Rocha

Four experiments were conducted in order to evaluate the effects of pesticides and three sulfur-base compounds in integrated mite management in Washington State. The effects of two neonicotinyl insecticides (acetamiprid and thiacloprid) and one insect growth regulator (novaluron) used in pheromone-based IPM for the control of codling moth, Cydia pomonella L., were tested. These experiments were conducted in six apple commercial orchards in 2006 and five in 2007. Phytophagous and predatory mite populations were assessed every 2-3 weeks from May to mid August and cumulative mite days (CMDs) calculated. From the six orchards that participated in 2006, four presented higher tetranychid mite densities in relation with the standard. In 2007, tetranychid mite populations were reduced drastically in relation to 2006 but still acetamiprid and novaluron had higher mite populations than the OP treatment. Predatory CMDs were similar in 2006 and 2007. In small-plot tests, tetranychid CMDs were higher in the treatment using two fruit thinners plus the codling moth insecticide (e.g., codling moth insecticide+ calcium polysulfide + carbaryl), suggesting an additive effect of multiple applications of disruptive materials. Treatments with two fruit thinners plus acetamiprid or novaluron had the highest tetranychid CMDs. A reduction on apple rust mite densities occurred when calcium polysulfide was added to the codling moth insecticides. In an experiment comparing three sulfur-based products (calcium polysulfide, ammonium thiosulfate and dry flowable sulfur), the disruptive effect of these compounds on predatory mites occurred after the first application, with all treatment 62-74% lower than the untreated check. The lethal effects of sulfur-based compounds on mortality and fecundity of twospotted spider mite, European red mite, and the predatory mite were assessed in a series of bioassays. Topical acute toxicity of calcium polysulfide and ammonium thiosulfate caused mortality of both phytophagous and predatory mites in about 48 h. European red mite was the most sensitive species to sulfur compounds, especially to ammonium thiosulfate, which killed 100% of the mites in the first 24 h. There was a difference in fecundity between the synchronous cohorts and the field collected females.

Effect of pesticides and three sulfur-based products on integrated mite management in Washington State

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