Acaricidal effect of Schinus molle (Anacardiaceae) essential oil on unengorged larvae and engorged adult females of Rhipicephalus sanguineus (Acari: Ixodidae)

The current concern about resistance to acaricides and the impact of toxic waste on the environment has led to the search of vegetal alternatives in the control of the brown tick of the dog Rhipicephalus sanguineus. Schinus molle L. (Anacardiaceae) derivatives have been associated with insecticidal, antimicrobial and antiprotozoal activities and essential oil showed to be lethal to R. microplus larvae. This study aimed at evaluating the acaricidal effect of essential oil of S. molle (EOSm) on engorged adult females and larval stages of R. sanguineus. One-hundred engorged females were obtained from the ears, interdigital spaces, neck, groin and base of the tail of two cross-bred dogs. The larvae package test was accomplished with 21-day-old larvae and five concentrations (v/v) of EOSm (0.125, 0.25, 0.50, 1 and 2%) in an anionic detergent, a synthetic acaricide (cypermethrin) and detergent and deionized water as controls. The immersion adult test was carried out with nine concentrations (0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 20%) of the EOSm. At the concentration of 2%, EOSm caused 99.3% of larval mortality. In adults, inhibition of oviposition, egg hatching (EH) and reproductive efficiency (RE) values were dose-dependent from 4 to 20% EOSm; the lowest values of EH (29.62) and RE (22.61) were achieved with 20% EOSm. Strong and negative correlations were found between concentration of EOSm and EH (r=-0.948) and between concentration of EOSm and RE (r = -0.985). This study demonstrated for the first time the acaricidal effect of EOSm on larvae and reproductive parameters of engorged adult females of R. sanguineus.