Neem based Larvicides

Larvicides are used for vector control under disease control programmes. It includes chemical larvicides, bio-larvicides and Insect Growth Regulators (IGRs). These compounds are generally nerve poisons and inflict mortality of mosquitoes at immature stages.

Larval control using neem-derived products offers a sustainable additional tool for malaria vector control. The efficacy of neem seed extracts has shown to degrade under exposure to sunlight within seven days and thus the toxicity is non-persistent in the environment. This not only provides environmental benefits but also means that regular applications of neem seed extracts would be required to maintain efficacy. Neem oil has good larvicidal properties for anophelines and suppresses successful adult emergence at very low concentrations.

Formulations such as Emulsifiable Concentrate (EC), Suspension Concentrate (SC) liquids etc. shall be applied to the habitats using a knapsack sprayer/ hand compression sprayer for which a prototype can be developed using NCVBDC guidelines to handle and to use insecticides. Other formulations such as granules, pellets, tablets and briquettes can be manually broadcasted or thrown into the water.

The impact of the larvicidal treatment is responsible to lower the density of adult mosquitoes resting indoors (human dwellings/ animal sheds), which can be measured by using hand catch method. This process provides information on the trend in the reduction of adult population of target mosquito species due to the effect of the larvicidal application.

Neem based larvicidal formulations developed by Institute of Pesticide Formulation Technology (IPFT) such as Suspension Concentrate, spreading oil and floating tablet formulation have been developed and scaled up. Suspension Concentrate formulation at 2.5% concentration and spreading oil formulation at 0.16% concentration resulted in optimum larvicidal effect. The doses will be further optimized during bio-efficacy data generation for registration.

Effect on non-target organisms:

The immediate predator of mosquito larvae is Poecilia fish (Poecilia reticulata) and the neem oil did not have any detrimental effect on longevity and survival of Poecilia fish. According to the several studies as referenced below, neem is found safe towards this fish and other non-target organisms including tadpoles and Gambusia affinis.