Production of two entomopathogenic Aspergillus species and insecticidal activity against the mosquito Culex quinquefasciatus compared to Metarhizium anisopliae

ABSTRACT

The spore productivity and insecticidal activity of two opportunistic insect pathogenic Aspergillus species (namely: Aspergillus clavatus Desmazieres and Aspergillus flavus Link (Ascomycota: Eurotiales, Trichocomaceae)) were compared to Metarhizium anisopliae sensu lato (Metchnikoff) Sorokin (Ascomycota: Hypocreales, Clavicipitaceae) for mosquito (Diptera: Culicidae) control. The production of aerial spores on wheat bran and white rice was investigated in solid-, semi-solid-, and liquid-state media supplemented with a nutritive solution. Wheat bran-based media increased the spore yield in solid-state from three to sevenfold: A. clavatus produced 48.4 ± 5.2 and 15.7 ± 1.6 × 10⁸ spores/g, A. flavus produced 22.3 ± 4.1 and 3.1 ± 2.5 × 10⁸ spores/g, and M. anisopliae produced 39.6 ± 6.5 and 13.1 ± 2.6 × 10⁸ spores/g of wheat bran or white rice, respectively. A. clavatus, A. flavus and M. anisopliae spores harvested from wheat bran-based solid-state media showed lethal concentrations (LC₅₀) of 1.1, 1.8, and 1.3 × 10⁸ spores/ml against Culex quinquefasciatus Say larvae in 72 h. Because A. clavatus and M. anisopliae displayed similar features when cultured under these conditions, our results suggest that insect pathogenic Aspergillus species may be as productive and virulent against mosquito larvae as a well-recognised entomopathogenic fungus.

KEYWORDS:

• Solid-state fermentation
• wheat bran
• white rice
• insect pathogenic fungi
• biological control
• Culicidae