Abstract
Nine ready-to-use pour-on formulations were tested for systemic control of an acaricidal-susceptible strain of Boophilus microplus (Canestrini); the active constituents were bromophos, bromophos-ethyl, bromophos-ethyl + chlorfenvinphos, chlorfenvinphos, chlorpyrifos, crotoxyphos, coumaphos, crufomate, dioxathion, and phosmet. These materials were tested in 5 field trials on Australian Itlawarra Shorthorn cattle naturally or artificially infested with ticks. Phosmet at 40 mg/kg and chlorpyrifos at 60 mg/kg give the best tick control (93-99% and 99% respectively), but poor results (17-59%) were obtained with phosmet at 60 mg/kg in one trial, and severe hair loss and skin burn occurred on all cattle treated with chlorpyrifos at 60 mg/kg. Pour-on applications of bromophos-ethyl gave 66-90% tick control, bromphos-ethyl + chlorfenvinphos 83-94%, crotoxyphos 66-89%, coumaphos (at 10, 15, 20 mg/kg) 17-84%, crufomate 64-89%, and dioxathion 79-92%. Coumaphos at 20 mg/kg produced symptoms of toxicosis in cattle immediately following treatment, and hair loss and skin burn occurred on cattle treated, with bromophos (slight), dioxathion (severe), and crufomate (severe). Female ticks were far fewer on untreated cattle during the 1st week posttreatment than during the pretreatment period. These reductions in number of ticks on untreated animals are thought to have been due to their contamination with the deposits of pour-on acaricides when all cattle were penned together prior to tick examination. Pour-on treatments were not as effective as spray applications for coumaphos and phosmet, but the pour-ons have special advantages and could be used under some circumstances.
Published Version
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