Background & objectives Use of microbial control agents provides alternative method for adequate insect management. We evaluated laboratory bioassay of Chilodonella uncinata, a natural protozoan parasite of mosquito larvae.

Methods Two formulations and four strains: North India (Monsoon and Pre-monsoon) strain, South India strain, updated strain of Chilodonella uncinata were tested against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti larvae at four institutes.

Results & Interpretation Delayed development was noted in mosquito larvae exposed to Ch. uncinata formulation that produced better effect in all larval species. Efficacy of this biolarvicide is not dose dependant as least dose produced maximum mortality with minimum post exposure. An. stephensi larvae were most sensitive followed by Cx. quinquefasciatus and Ae. aegypti which required longer post exposure. Of the four strains, updated strain was most effective and stable; south India strain had rapid killing effect; Pre-monsoon strain was more effective than Monsoon strain as the later required 20x higher dose (cs/ml) to induce satisfactory mortality in An. stephensi larvae with higher values for LT₅₀ (4.71) and LT₉₀ (6.84) as against LT₅₀ (2.5) and LT₉₀ (3.57) of former strain. Tea bag formulation is easy to store, transport and treat, was found to have a shelf life of >18 months resulting in satisfactory efficacy against An. stephensi with LT₅₀ (5.16) and LT₉₀ (7.69) noted at 0.25 g even after 6 months of storage. These laboratory test data suggest that a lower dose of this protozoan formulation can be used as a potential biolarvide to control mosquito larvae as an alternative to chemical insecticides under integrated vector management.