Efficacy of Metarhizium anisopliae [Metchnikoff] Sorokin in a biological control agent ofCulex quinquefasciatus Say [Diptera: Culicidae] with histological study of infected larvae

Abstract

Efficacy of serial concentrations of Metarhizium anisopliae were measured against eggs, larval instars, pupae and adults of Culex quinquefasciatus under labolatory conditions. The results showed that all insect stages were sensitive to the fungal concentrations 2.5 × 106 , 2.5 × 107 and 2.5 × 108 conidia/ml. Treating eggs with 2.5× 108 conidia/ml caused reduction its hatching percentage up to 71.03% and treating second and fourth instars larvae by mixing their foods with of M. anisopliae conidia led to ccumulative high mortality percentage reached to 100% when treating the second instar with the concentrations 2.5 × 106 and 2.5 × 108 conidia/ml. , various malformation were depicted. Infected larvae showed symptoms of sluggishness and slow in growth. Histopathological study of the dead larvae showed conidial chains in the haemocoel and the mid gut was full with conidia that mixed with food and a decomposition of walls, the blastospores were found surrounded the mid gut and a decomposition in the muscle tissue with its absence of fungal filaments. Treating mosquito pupae with 2.5 × 106 conidia/ml of M. anisopliae had an average of 65.47% mortality and various malformation level were depicted. Adult stage showed a high sensitivity against fungal conidia concentrations to ccumulative high mortality percentage reached to 100% when treated with 2.5 × 108 conidia/ml.