The mixture of the acaricides dicofol and fenpyroximate for managing resistance of Brevipalpus phoenicis (Geijskes) to dicofol was evaluated. First, we analyzed the interaction of dicofol and fenpyroximate by testing the LC25s of each product for both susceptible (S) and dicofol-resistant (R) strains of B. phoenicis. Synergistic interaction was detected with the mixture for both strains. Then, the persistence of the biological activity of residues of dicofol (at recommended rate of 360 g of active ingredient (A.I.) / 1,000 L of water), fenpyroximate (at 50 g of A.I. / 1,000 L of water) and the mixture of dicofol and fenpyroximate (at 240 and 25 g of A.I. / 1,000 L; respectively) was evaluated in a commercial citrus grove. After application of the products, fruits were collected periodically and infested with mites of S and R strains in the laboratory. Residues of dicofol and the mixture discriminated the strains; that is, higher mortality of S strain in relation to R strain was observed throughout the experiment. Residues of fenpyroximate did not discriminate the strains, however, fenpyroximate by itself did not give an acceptable control of B. phoenicis. The sinergism between dicofol and fenpyroximate was not effective for managing resistance of B. phoenicis to dicofol.
Citrus leprosis mite; Citrus sinensis; chemical control; synergism
