Study on the acaricidal effects of Azadirachta indica and Phytolacca dodecandra on Amblyomma ticks in Ethiopia

Abstract

A study was carried out to investigate the acaricidal effect of extracts of Azadirachta indica (neem) and Phytolacca dodecandra (locally known endod in Ethiopia) on Amblyomma cohaerens and Amblyomma variegatum. An adult stage of A. cohaerens was collected from east Wollega zone of the Oromia region of Ethiopia and the larval stage of A. variegatum was obtained from tick rearing unit of the National Animal Health Diagnostic and Investigation Centre (NAHDIC), Sebeta, Ethiopia. Neem seed was  collected from Awash town of the Afar region. Berries of endod from Aklilu Lemma Institute of  Pathobiology and commercial neem oil were obtained from India. The water extract of the two plants at doses of 18,750 ppm, 37,500ppm, 75,000 ppm, 150,000 ppm and 300,000 ppm were tested on Petri dish and using the immersion method. The result showed that, neem seed water extract produced mortality rate of 16.6% on adult stage of A. cohaerens at a dose of 300,000 ppm. The LD50 indicated a dose of 370,854.7 ppm and no statistically significant (p>0.05) difference was observed among the two methods of applications. The same extract in both methods of application produced a mortality rates of 8.3%, 16.6% and 41.6 % at doses of 75,000ppm, 150,000ppm and 300,000ppm  respectively on A.variegatum and the probit analysis indicated LD50 of 366,64ppm. Endod extract did not produce any mortality at all doses tested on both species of ticks. Neem oil was also evaluatedat a concentration of 20%, 40%, 60%, 80% and 100%. At 100% concentration, the oil caused 50% mortality on adult of A. cohaerens whereas 20% concentration resulted  in 8.3% mortality rate. Likewise, 100%, 100% and 75% mortality rate on A. variegtum was observed at 100%, 80% and 20% concentrations of the oil respectively. Probit analysis indicated LD50 value of 11.7%  concentration. The water extracts of both plants did not  produce 100% efficacy while promising results were obtained by neem oil on larva of A. variegatum at high concentrations.

Keywords: Acaricidal effect, Amblyomma variegatum, Amblyomma cohaerens, Azadirachta indica (neem), Phytolacca dodecandra (endod)