Acaricide AC 84,633: First Trials for Control of Boophilus microplus1

A new acaricide, American Cyanamid AC 84,633 (Imidocarbonic acid, (4-chloro- o -tolyl)-dithio-, cyclic methylene ester) inhibited oviposition and reduced egg hatchability in in vitro tests with the southern cattle tick. Unfed larvae were paralyzed but not killed by concentrations up to 64000 ppm. In 2 experiments conducted on stalled cattle experimentally infested with either an organophosphate-susceptible or resistant strain of B. microplus , minimum control was 99.6 and 99.8%, respectively, from spray concentrations of 454 and 500 ppm of AC 84,633. Cattle with heavy experimental infestations were maintained under field conditions after a single spray or dip treatment. From days 2–21, mean tick mortality was 92.4% on cattle sprayed with 500 ppm and 95.7% on cattle dipped with 464 ppm. From 5–21 days, mean tick control was 97.7 and 99.7% for sprayed and dipped cattle, respectively. The foregoing results were confirmed during large-scale dipping trials on farms with histories of difficult tick control.