Efficacy and biological effects of Neem products against mosquitoes of medical importance

Mosquitoes cause health problems worldwide as vectors of deadly communicable diseases like malaria, dengue, yellow fever, West Nile. Control programs mainly rely on chemical insecticides led to development of biological resistance along with environmental adverse effect. 

In recent years, huge efforts have been carried out to develop eco-friendly alternatives, with special focus on botanical derivatives. Among them Neem-based products (Azadirachta indica seem hopeful, showing ovicidal, larvicidal and pupicidal and repellency effect on mosquitoes of medical importance like Aedesspp, Anophelesspp, Culexspp and Mansoniaspp. Azadirachtin is predominant insecticidal active ingredient in seed, leaves, and other parts of Neem tree.

We evaluated the toxicity effect of an Azadirachtin-rich formulation named Neemarin (Biotech International Limited, New Delhi, India) on lab bred Anopheles stephensiand Culex quinquefasciatus larvae, also in the field (south of Iran) in artificial breeding places. LC50 and LC90 values for Neemarin were 0.35 and 1.81 mg/L for An. stephensi, the main local malaria vector, and 0.69 and 3.18 mg/L for Cx. quinquefasciatus. The mortality in the pupal stage was significantly higher. In field trials, using recommended dosages (1 and 2 L/hectare), mortality of Anophelesspp. larvae was also higher than Culexspp. Prevention of adult emerged and pupal mortality was the main activity. The maximum time of efficacy was 7 days at the highest concentration (2 L/hectare). The short life time of Neem product makes it ineffective under atmospheric, but many of its new formulations have been reported to remain stable under environmental conditions.