Larvicidal effect of metarhizium anisopliae conidia against Aedes albopictus

Aedes albopictus is a mosquito species that can be commonly found in Malaysia. Study shows that Ae. albopictus can act as a vector that can potentially transmit dangerous diseases such as dengue and heartworm. Thus, chemical control was made to combat the increase in the population of mosquitoes. However, due to increased reports of resistance and toxicity effects, new control methods have been developed to replace the negative effect. Several studies show that entomopathogenic fungi such as Metarhizium anisopliae can be used as a biological control against Ae. albopictus. Thus, this study was conducted to determine the efficacy of M. anisopliae against Ae. albopictus. Secondary cultures of M. anisopliae were performed to collect the conidial suspension. A larvicidal bioassay based on the WHO standard was conducted with different treatment concentrations (101,103 and 105 conidial/ml). The observations were recorded for seven days, and the data were analysed using ANOVA and Probit analysis. The median lethal concentration (LC50) and lethal concentration 90 (LC90) for the conidia suspension were 9.93x102 conidia/ml and 1.5x104 respectively. Whereas the median lethal time 50 (LT50) for the concentrations of 101, 103 and 105 are 14.05 days, 13.24 days, and 2.20 days and the median lethal time (LT90) is 25.6 days, 23.7 days and 3.3 days. The ANOVA result shows that there are no significant different between the concentrations of treatments and larval motility with P value > 0.05. However, this study proves that M. anisopliae has an effective effect against Ae. albopictus larvae which could be developed as a potential bio-insecticide for Ae. albopictus control.
Keywords: Aedes albopictus, Metarhizium anisopliae, biological control, larvicidal bioassay.