COMPARATIVE EFFECTIVENESS OF COUMAPHOS TREATMENTS APPLIED BY DIFFERENT METHODS FOR THE CONTROL OF BOOPHILUS-MICROPLUS (ACARI, IXODIDAE)

Effectiveness of coumaphos applied by three different treatment method s (dipping vat, spray-dip, and power spray) to cattle infested with pa rasitic stages (adult, nymphal, and larval) of Boophilus microplus (Ca nestrini) was studied. Both the number of ticks per calf and the index of reproduction (IR) of engorged females recovered from untreated cal ves were significantly higher (P < 0.05) than from treated calves, reg ardless of the developmental stage of the ticks or the method of apply ing the acaricide, indicating that coumaphos had a dramatic adverse ef fect on ticks. When adult ticks were subjected to the dipping vat meth od of treatment, both the number of females recovered (54 ticks/calf) and the IR (0.0) were significantly lower (P < 0.05) than those of adu lt ticks subjected to spray-dip (146 ticks/calf; IR = 118,253) or powe r spray treatments (199 ticks/calf; IR = 289,198). The trend was repea ted in ticks that were in the nymphal stage at the time of treatment, indicating that the dipping vat method (1 tick/calf; IR = 0.0) was mor e effective than either the spray-dip (54 ticks/calf; IR = 38,014) or power spray treatments (96 ticks/calf; IR = 115,945). Likewise, the di pping vat method was more effective (0 ticks/calf; IR = 0.0) than the spray-dip (23 ticks/calf IR = 7,426) or the power spray (57 ticks/calf ; IR = 23,848) when ticks were in the larval stage of development at t he time treatments were applied. Although all three treatment methods were successful, the dipping vat method reduced tick numbers and repro duction more effectively than spray-dip or power spray. Because the ob jective of any eradication program is the complete elimination of tick s, treatment in a dipping vat would be the most desirable method.