Alternative strategic control of Rhipicephalus microplus in the Cerrado of Minas Gerais, Brazil, by exploiting abiotic conditions.

Abstract

This study compared four strategies for controlling Rhipicephalus microplus in steers under field conditions in the savannah Biome (Cerrado) of Brazil, including two control groups: traditional strategic control (T1), palliative control (T2), an alternative experimental strategic control (T3), and pasture spelling during the dry season (T4). Twenty-four Girolando steers were allocated into four groups (n = 6) and monitored for tick infestation over an 11-month period. Efficacy was assessed using cumulative and monthly tick counts on steers, tick-free periods, and indicators of pasture disinfestation. Mean cumulative counts of ticks per animal were 10.3 (T1), 33.5 (T2), 10.2 (T3), and 10.1 (T4), corresponding to reductions of 69.3 %, 69.6 %, and 69.9 % in T1, T3, and T4, respectively, relative to the palliative control. Aggregated tick counts were significantly higher only in T2, whereas all strategic approaches resulted in similarly lower overall infestation levels. Tick-free periods differed markedly among treatments: T1 achieved the longest cumulative tick-free period (169 days), followed by T3 (142 days, occurring in two discontinuous phases) and T4 (134 days), while no sustained tick-free period was observed in T2. Notably, pasture spelling produced the longest tick-free period independent of residual acaricide activity (64 days). The non-parasitic phase of tick populations was suppressed during the cold and dry season. From May to August, larval production and survival in the field were reduced by 89.3 % and 67 %, respectively. Pasture infestation declined during spelling, attaining absence of larval clusters after 99 days of cattle removal. Overall, pasture spelling provided tick control comparable to acaricide-based strategies while substantially reducing chemical use.