D3010: Larvicidal effects of low concentrations of Beauveria bassiana against Aedes albopictus (Diptera: Culicidae)

Aedes albopictus (Skuse, 1895) has become a broadly distributed mosquito bringing dengue virus transmission to new areas. Current management tactics such as larvae habitat reduction and chemical pesticides have failed to alleviate the biting pressure, calling for 21^st century strategies using biological control. The use of a naturally occurring entomopathogenic fungus, Beauveria bassiana, has shown efficacy in other insect pests and can be harnessed for use against mosquito vectors. This study investigates mortality of Ae. albopictus larvae when exposed to various concentrations of B. bassiana using a commercially available product, Mycotrol ESO®. We performed a bioassay using second and third instar Ae. albopictus in B. bassiana with concentrations of 1x10⁴, 1x10⁵, 1x10⁶, 1x10⁷, 1x10⁸ conidia/ml and control without B. bassiana. Each concentration consists of four containers with 25 larvae and 100 ml of fungus-infused water. Larvae were monitored for mortality every 24 hours for 12 days. The experiment was repeated three times with a total of 300 larvae for each concentration. A Kaplan-Meier survival analysis showed larvae mortality was concentration dependent (log-rank test, p < 0.0001). Lethal concentrations at day 12 were 2.43x10⁵, 6.65x10⁵, and 1.01x10⁶ conidia/ml for LC₅₀, LC₉₀, and LC₉₉, respectively. Median lethal time at 1x10⁵ conidia/ml was 11.8 days and at 1x10⁶ conidia/ml was 3.68 days. We conclude that concentrations above 1x10⁶ conidia/ml of B. bassiana work efficaciously as larvicide on early instar Ae. albopictus. Entomopathogenic fungi have potential for use in vector control and should continue to be explored in the field.