Uso de diferentes reguladores de crescimento como alternativa no controle de Rhipicephalus microplus

Abstract

In order to evaluate the in vitro efficacy, on the engorged females of Rhipicephalus microplus, of the growth regulators fluazuron, piriproxifen and diflubenzuron in three tests carried out with different solubility methodologies and immersion time. Assays in vitro were performed with ticks from the Porto Alegre strain. The solubility methodologies used for the three tests were as follows: in the first test, fluazuron 10% emulsifiable concentrate was used, and for the pyriproxyfen and diflubenzuron, solubilized feedstock was used in Triton-X 100 10% and xylol, a dilution also in distilled water. In this assay the following concentrations were analyzed for the three growth regulators 7.000, 6.000, 5.000, 4.000, 3.000, 2.000, 1.000, 500, 250 and 125 ppm. In the second assay fluazuron and pyriproxyfen solubilized in Triton-X 100 and N-methylpyrrolidone and diflubenzuron 1% emulsifiable concentrate were also used, also with the serial dilution in distilled water. In this, different concentrations were used for the growth regulators; for fluazuron the concentrations were 4.000, 3.750, 3.500, 3.000, 2.750, 2.500, 2.000, 2.250, 2.000, 1.750, 1.500, 1.250, 1.000, 750, 500, 250, 100 and 50 ppm, for piriproxifen 13.000, 12.000, 11.000, 10.000, 9.000, 8.000, 7.000, 6.000, 5.000, 4.000, 3.000, 2.000, 1.000, 500, 250, 100 e 50 ppm and for diflubenzuron 10.000; 9.000; 8.000; 7.000; 6.000; 5.000; 4.000; 3.000; 2.000; 1.000; 500; 250; 125 and 62,5 ppm. In the third and final assay, fluazuron, piriproxifen and diflubenzuron diluted in Triton-X 100, N- methylpyrrolidone and acetone with the serial dilution performed with the diluent. The concentrations in ppm in the third assay were the same for the three growth regulators, 4,000; 3,000; 2,000; 1,000; 500; 100; 50; 25; 1; 0.5; 0.1; 0.05 and 0.01 ppm. To perform the in vitro assay the engorged females were immersed at different concentrations for different times, in the first study for five minutes and in the two following for one minute, after drying and weighing were individually packed in petri dish for 21 days for weighing of the respective postures. Afterwards they were stored for another 21 days to read the percentage of hatching. As result, fluazuron showed 100% efficacy in all three trials, especially at the highest concentrations. Pyriproxyfen had the highest efficacy in the last trial, with 89% at 3,000 ppm, however, in the other trials, it showed approximately 70% efficacy at the highest concentrations in all three trials it was observed that pyriproxyfen reduced the weight of the postures. And diflubenzuron was more effective in the first study, however, the solubility of this drug was not adequate. In the second and third trials the efficacy was found to be less than 40%. Thus it is possible to conclude that the different results on the weights of the postures from the engorged females, such as the different hatching percentages, the reproductive efficiency indices and the efficacies for the growth regulators used were due to the methodologies of solubilization of the raw material.