Laboratory and field preliminary tests of Metarhizium anisopliae formulated with neem oil (Suneem) against Anopheles gambiae sl adult emergence

Metarhizium anisopliae have shown great potential for the control of malaria vectors. However, their ability to control aquatic stages of anopheline vectors with conidial formulation is need. In laboratory condition (25°C and 76%RH), we formulated M. anisopliae with emulsifian neem oil (Suneem 1%) before application on An. gambiae larvae at 4, 6, 8, 10 and 12 % (v/v) to determine the LD90. We applied in semi-field environment, the LD90 of the formulation into artificial vats on the Anopheles gambiae sl larvae collected from many breeding sites at dry and rain seasons.
In laboratory condition, the LD 50 was 4.4 x 10^6 spores/ml and the LD90 was not obtained 24 after exposure. The probite line equation was Y=1.61 x – 0.55 and R²= 0.9793. The LD 50 was 3.1 x 10^6 and the LD90 was 5.3 X 10^6 spores/ml 48 h after exposure. The probite line equation was then Y= 1.69 x + 1.79 and R²= 0.9757. Microscope magnifying revealed also the fungal attack via cuticle and mycelia germination one dead larvae and pupae.
In semi-field environment, treatment revealed that, at 5.3 x 10^6 spores/ml, the formulation has a great emergence inhibition of mosquito adult formation. No significant difference was observed between dry and rain season application of M. anisopliae on the larvae. Therefore, a combination of M. anisopliae with Suneem may provide a more sustainable management strategy for malaria vectors control at the larval stages.