In Vitro Acaricidal Activity of Crude Methanolic Extract of Leaves of Parthenium hysterophorus
A study was conducted to investigate in vitro acaricidal activity of crude methanolic extract of leaves of Parthenium hysterophorus against three ixodid cattle ticks, namely Amblyomma variegatum, Amblyomma cohaerens, and Rhipecephalus decoloratus. The ticks were collected from cattle kept at Haramaya university beef farm for fattening, which were purchased from different markets of Eastern Hararghe zone. Standard physical and direct stereomicroscopy techniques were employed for identification of ticks. The adult ticks were exposed to six graded concentrations of the extract in triplicates; 200mg/ml, 100mg/ml, 50mg/ml, 25mg/ml, 12.5mg/ml, and 6.25mg/ml for 24hrs using in vitro adult immersion test. Mortality rates were recorded at 30min, 1hr, 2hrs, 3hrs, 6hrs, 12hrs and 24hrs post exposure. Diazinon (0.1%), and distilled water were used as positive and negative controls, respectively. Acaricidal activitiy of the extract concentrations was measured by mean number of ticks died and acaricidal efficacy (%) relative to the negative control. The result showed time and concentration dependent acaricidal activity of the extract. Mean mortality showed significant difference between higher dose (200mg/ml) and lower doses (p<0.05). It was also noted that ticks exposed to higher concentration of extract showed greater mean mortality compared to diazinon. Extract diluted to 200mg/ml caused 100%, 100%, and 86.7% while diazinon 91.6%, 95.8%, and 71.1% deaths of A. variegatum, A. cohaerens, and R. decoloratus during 24 hrs, respectively. This preliminary work suggests that leaves of P. hysterophorus possess a promising acaricidal potential warranting a follow up work encompassing in vivo toxicity and efficacy tests.