Volume 208, Issues 3–4, 15 March 2015, Pages 225–230
Highlights
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- Strategic applications of long acting acaricides against Rhipicephalus microplus were evaluated.
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- The overall treatment effect was positively significant in the two schemes evaluated.
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- Tick distribution was markedly aggregated.
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- Individual composition of the most heavily infested group was not consistent across the time.
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- Level of aggregation varied with the abundance of ticks.
Abstract
Strategic applications of long-acting acaricides for the control of Rhipicephalus (Boophilus) microplus
in northwestern Argentina were evaluated for one year. In addition,
tick distribution among cattle was analyzed to evaluate if partial
selective treatment or culling the small proportion of most heavily
infested animals were feasible options to control R. (B.) microplus.
Two different treatments schemes based on two applications of fluazuron
and one application of 3.15% ivermectin were performed. Treatments were
made in late winter and spring so as to act on the small 1st spring
generation of R. (B.) microplus, in order to
preclude the rise of the larger autumn generation. The overall treatment
effect was positively significant in both schemes. The number of ticks
observed in the control group was significantly higher than in the
treated groups on all post-treatment counts. Group 2 exhibited more than
80% of efficacy almost throughout the study period, whereas Group 1
exhibited an efficacy percentage higher than 80% in September, October,
December, February, April and May, but not in November (73.4%), January
(58.3%), March (45.2%) or June (53.4%). Absolute control was observed in
Group 2 in the counts of September and October, and in Group 1 in the
count of February. The control strategies evaluated in this work provide
an acceptable control level with only three applications of acaricides;
at the same time, they prevent the occurrence of the autumn peak of
tick burdens, which is characteristic of R. (B.) microplus
in northwestern Argentina. Tick distribution was markedly aggregated in
all counts. Although ticks were not distributed evenly among calves,
the individual composition of the most heavily infested group was not
consistent throughout the study period. In addition, the level of
aggregation varied with tick abundance. These results suggest that
applying acaricides to a portion of the herd or culling the most
infested individuals at a given moment of the year may not be proper
methods to achieve a significant control of R. (B.) microplus in northwestern Argentina.
Keywords
- Rhipicephalus microplus;
- Control;
- Ivermectin;
- Fluazuron;
- Tick distribution;
- Argentina
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