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Title: Suppression of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) on Pastured Cattle Using Abamectin-Impregnated Cattle Ear Tag

Author
item Davey, Ronald
item Pound, Joe
item Lohmeyer, Kimberly - Kim

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2012
Publication Date: 4/1/2013
Citation: Davey, R.B., Pound, J.M., Lohmeyer, K.H. 2013. Suppression of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) on pastured cattle using abamectin-impregnated cattle ear tag. Journal of Entomological Science. 48:99-113.

Interpretive Summary: While USDA-APHIS-VS mandatory eradication procedures provide the means for eliminating cattle fever ticks in quarantined pastures, they provide no measures for preventing or reducing the risk of dispersing ticks into un-infested adjacent pastures stocked with cattle. Thus, the efficacy of an abamectin-impregnated Cattle Ear Tag (Y-Tex® XP 820™) was evaluated in a 40-week study to determine the suppression capability of the tags against a southern cattle tick population on cattle maintained on tick infested pasture. Results showed that during the spring through early summer months (March-June), when temperatures were ideal for tick survival, the level of control was low (<54%). However, during the summer through mid-fall months (July-October), when high temperatures caused a natural and dramatic decline in the tick population, the level of control reached 100% on several occasions, and was >72% throughout this period. Furthermore, during the late fall and mild winter months (November-February), when temperatures were again conducive to tick survival, results showed that the presence of ear tags on treated animals prevented the dramatic build-up of ticks observed on untreated animals. Results demonstrated that while the ear tags would not be adequate for eradicating a tick population, if ear tags were applied at the appropriate time, a reasonable level of control could be expected. In addition, tags applied in the summer through fall months would likely prevent a dramatic buildup of ticks on the animals that would normally occur during the subsequent spring. Therefore, the use of the ear tags in adjacent pastures would at least reduce the risk of dispersing large numbers of ticks into un-infested areas.

Technical Abstract: Efficacy of Y-Tex® XP 820™ Cattle Ear Tags containing 8% abamectin and 20% piperonyl butoxide was evaluated against the southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini) during a 40-week field study. Temperature fluctuations had an important impact on efficacy of the ear tags. During the first 19 weeks, in the spring and early summer months (March-June), conditions were optimum for tick survival, resulting in high tick numbers on treated animals (9-63 ticks per animal) that were not different from untreated animals. During this time, ear tags provided = 53.7% control. However, during the summer through mid-fall months (July-October), high temperatures resulted in dramatic natural declines in the tick population, and tick numbers on treated animals were much lower (0-3 ticks per animal) than those of untreated animals (4-16 ticks per animal). During this period ear tags provided 72-100% control, indicating that the ear tags had a negative impact on tick survival that was greater than the natural decline caused by the high temperatures. During the last 9 weeks (mid-October to mid-December), temperatures were again highly conducive to tick survival, and tick numbers on untreated animals rebounded (7-56 ticks per animal), whereas treated animals produced fewer ticks (1-9 ticks per animal) resulting in 73-98% control, indicating the ear tags prevented the rebound of tick numbers. The study demonstrated that timing of ear tag application was critical to the level of efficacy. Tags applied in spring or early summer provided a low level of control, whereas tags applied in summer and early fall provided a high level of control. In addition, ear tag application in summer or fall months would likely prevent the enormous buildup of ticks that would occur the following spring if tags were not used.