Abstract
Insecticides play a major role in the control of mosquitoes but due to rapid resistance development, toxic effects on the environment and human health, there is an increasing need to concentrate on the development of medicinal plant-based natural insecticides. Essential oils were extracted from two medicinal plants, Allium sativum and Zingiber officinale, and were evaluated for larvicidal and repellent activities against mosquito disease vector species; Aedes aegypti and Anopheles stephensi, according to the bioassay guidelines of World Health Organization. The extracted oil of A. sativum showed toxicity against the third instar larvae of A. aegypti with LC50 of 0,314 and LC90 of 12,323 after 24 hours. Similarly, the LC50 was 0.40 and LC90 were 2.13 after 24 h against An. stephensi. The extracted oil of Z. officinale showed toxicity against third instar larvae of A. aegypti with LC50 value of 186,33 and LC90 value 11602.4 after 24 h against A. aegypti while LC50 value 43.14 and LC90 value 6453.54 after 24 h against An. stephensi, respectively. The aqueous extracts of A sativum and Z. officinale have a lower repellent effect against A. aegypti and An. stephensi when compared with Mospel (DEET). A. sativum oil extract resulted into the highest repellent effect at 20% dose with a mean protection time of 130 and 140 minutes, while Z. officinale gave 80 and 90 min protection time against both An. stephensi and A. aegypti adults, respectively and Mosper (DEET) had 7.5-8 hours of protection. Our results revealed that A. sativum oil had a strong insecticidal effect while Z. officinale had not exhibited significant activity against both tested mosquito species. As repellent, aqueous extract was less effective when compared with gold standard DEET and both plants extract needs to be furthered evaluated under field conditions as insecticides as well as for improved repellent efficacy.