Acaricidal Activity of Some Medicinal Plant Extracts against Different Developmental Stages of the Camel Tick Hyalomma dromedarii

The pesticidal effect of petroleum ether and ethyl alcohol extracts of Melia azedarach and Artemisia herba-alba against active stages (larvae, unfed adults and engorged females) of the camel tick Hyalomma dromedarii was evaluated by larval and adult immersion tests. Extracts were subjected to gas chromatography-mass spectrometry to identify the major active constituents. Histological sections of semifed females were evaluated to monitor the changes occurring in the cuticles and guts. The LC50 values indicated that the petroleum ether extract of A. herba-alba was more toxic against larvae (1.83%), followed by unfed adults (2.37%) and then engorged females (3.1%). However, the petroleum ether extract of M. azedarach exhibited its activity in the reverse order, i.e., it was more toxic against engorged females (3.96%), followed by unfed adults (5.47%), and then larvae 10.99%. The LC50 values of the ethyl alcohol extracts of A. herba-alba and M. azedarach on larvae, unfed adults, and engorged females were 19.60% and 22.75%, 79.81% and 19.44%, and 29.63% and 11.1%, respectively. The egg productive index (EPI), egg number, and hatchability percentage were low in the treated females. Abnormalities were observed in the cuticles and guts after treatment with plant extracts. In conclusion, the two plants M. azedarach and A. herba-alba exhibited good acaricidal activities against the active stages of H. dromedarii and might be used in the control of the camel ticks.