Vineyard and Laboratory Evaluations of Methomyl, Dimethoate, and Permethrin for a Grape Pest Management Program in the San Joaquin Valley of California

Abstract

The impact of dimethoate, methomyl, and permethrin upon target and nontarget arthropods was determined through laboratory and vineyard tests. All compounds controlled a leafhopper, Erythroneura elegantula Osborne, in vineyard trials. Permethrin only was tested against the grapeleaf folder, Desmia funeralis (Hübner). The impact of these 3 materials upon the nontarget mite species differed. Dramatic increases of the Pacific spider mite, Tetranychus pacificus McGregor, followed permethrin treatments in vineyards at 1,5,3,6, and 12 g AI/100 liters. Laboratory LC50 data showed that the Pacific spider mite is tolerant to low-moderate rates of permethrin while its phytoseiid predator, Metaseiulus occidentalis (Nesbitt), was extremely susceptible. The tydeid, Pronematus anconai Baker, which serves as alternate prey for M. oecidentalis was very susceptible to permethrin, but tolerated methomyl and dimethoate in laboratory trials. Methomyl treatments increased the Pacific spider mite and Eotetranychus willamettei McGregor populations in vineyards although M. oceidentalis numbers began to increase 10 days after treatment and the spider mite numbers reached were lower than in the blocks treated with permethrin. Laboratory tests showed that M. occidentalis was very susceptible to methomyl, but dimethoate resistance was found in the majority of vineyard colonies tested. Dimethoate exhibited moderate acaricidal activity against the Pacific spider mite in the vineyard.