MANAGEMENT OF CITRUS RUST MITE (ACARI, ERIOPHYIDAE) RESISTANCE TO DICOFOL IN FLORIDA CITRUS

Cage and field studies of the dynamics of the citrus rust mite, Phyllo coptruta oleivora (Ashmead), resistance to dicofol appeared to be unst able; tile frequency of resistance declined quickly in the absence of selection pressure. Different regimes for dicofol (twice per year, onc e per year, dicofol after 2 yr of its relaxation, and untreated contro l) were evaluated in Florida in 2 commercial citrus groves during 1990 , 1991, and 1992 seasons. We detected a positive relationship between the number of dicofol applications made per year and the frequency of resistance to dicofol. Differences in the frequencies of dicofol-resis tant mites in bioassays reflected differences in the field performance of dicofol. Use of dicofol twice per year was not appropriate because of an increased trend in die frequency of resistance from one year to the next. However, using dicofol once per year, the frequency of resi stance to dicofol returned to a level equal to or less than the freque ncy before selection after approximate to 12 mo of dicofol application . We recommend resistance management program for dicofol for Florida c itrus.