Bioacaricidal effects of three volatile oils on cattle ticks

Use of synthetic chemicals in addressing livestock attacks by ticks has negative effects on animals, handlers and the environment. These problems necessitate search for potent alternatives in bioacaricides particularly volatile oils. Acaricidal effects of hydro-distilled volatile oils from the fresh leaves of Eucalyptus citriodora, Ocimum gratissimum (OG) and Callistemon citrinus were evaluated on ticks obtained from infested cattle using topical method at varying concentrations in acetone. For each concentration, ten ticks of similar species were placed in Petri dishes and administered 20μL of the mixture of volatile oil and acetone. Acetone (20μL) was used as control and the effects were observed for 24 h. Out of three tick species identified, Rhipicephalus microplus was most abundant and most sensitive to the oils. Others are Amblyomma hebraeum and Hyalomma rufipes (most resistant). The volatile oil of OG was the most potent with LC50 of < 2 % (< 0.4 μL), < 2 % and 7.97% (1.59 μL) on the organisms respectively. The 5% of OG produced 100% mortality on R. microplus in 10-25 min while 20% concentration produced 100% mortality on H. rufipes in 24 h. Volatile oils of these plants particularly OG can serve as potent alternative bio-acaricidal agents to chemicals.