Determination of the susceptibility of unengorged larvae and engorged females of Rhipicephalus microplus (Acari: Ixodidae) to different methods of dissolving thymol

The present study evaluated efficacy of thymol against engorged females and unengorged larvae of Rhipicephalus microplus when diluted in 1 % dimethyl sulf- oxide (DMSO) (formulation 1) and diluted in hydro-ethanol solutions of 50 % (formulation 2), 40 % (formulation 3), and 30 % (formulation 4). The immersion test was used on the engorged females for all dilution methods, while the larval packet method was applied to the larvae to test formulations 3 and 4 since the other two had already been tested before. Two control groups were established in both experiments; in one, ticks were treated with 1 % DMSO, and in the other, with 50 % ethanol, with ten repetitions for each treatment. The groups were maintained at 27±1 °C and RH>80±10 %. For engorged females, the parameters weight before oviposition, egg mass weight, hatching percentage of larvae, and percent- age of control were evaluated, while for larvae, percentage of mortality was evaluated. The egg mass weight of all treatments differed significantly (p 0.05). The group treated with formulation 2 attained the lowest percentage of control (66 %). In the other treatments, the control percentages were greater than 99 %. In larval test, the mortality was100% inall thetreatments, andtherewas no mortality in the control groups.