Allium sativum extract against free-living larvae of Rhipicephalus microplus: a potential environmental biocontrol.

Abstract

The infestation of Rhipicephalus microplus (Acari: Ixodidae) (Canestrini, 1887) represents a significant health problem for cattle. Up until today, no consistent control has been recommended for the free-living larval stage of R. microplus. The objective of the present study was to determine the larvicidal effect of an Allium sativum (garlic) aqueous extract against R. microplus using the larval package test, LPT. Tick larvae were obtained from adult female ticks from naturally infected animals, and 200 larvae were exposed to each A. sativum extract concentration (5, 7, 10, 16, 25, and 50%). All garlic groups received the extract in three different volumes (2, 5, and 7ml) to determine the levels of humidity that would affect the free-living stage. Larvae from the control group were treated with distilled water and the positive control used cypermethrin in a 5-ml volume. Live and dead larvae were determined after 24h of exposure. There was a significant statistical difference (P=0.041) at 5% between 2 and 5ml and between 7 and 10% of the extract using 2ml (P=0.034). There was a significant larvicidal activity of 100% mortality for the 16, 25, and 50% concentrations for all volumes. We observed a clear concentration-dependent effect for the extracts with a correlation coefficient of R2>0.92. The lethal concentration of 50% (LC50) was 13.6, 9.8, and 7.6% for the 2, 5, and 7ml. The present A. sativum solutions may be considered a viable biofriendly alternative to reduce the number of the free-living larval stage of R. microplus on pasture and the consequent reduction of cattle infestation due to its high larval mortality.