Effects of culture medium and formulation on the larvicidal activity of the mosquito pathogen Lagenidium giganteum (Oomycetes: Lagenidiales) against Aedes aegypti

In this work, we examined the production of infective zoospores of Lagenidium giganteum in four culture media, and the larvicidal activity of the cultures was determined against Aedes aegypti larvae, as well as the effect of polymer encapsulation. Medium containing sunflower seed extract showed the greatest production of zoospores, 5.92 × 106 zoospores/ml after six days of fermentation at 25 ± 2 °C and 150 rpm shaking. This culture tested against A. aegypti 1st stage larvae caused different mortality rates at 24, 48 and 72 h posttreatment. The LC50 obtained was 43.9, 41.1 and 42.9 μl of total culture/ml, at 24, 48 and 72 h posttreatment respectively, while the culture grown in medium with soybean meal showed 3–5 times higher LC50 values. Finally, the total culture including mycelium, zoospores and presporangia formulated with 2.5% pectin showed significantly higher mortality rates, around 100% more than the unformulated culture, whose values were from 40 to 1% at 3, 6, 9, and 12 d posttreatment in the bioassays carried out in the laboratory to determine residual activity.