Laboratory studies on the recycling potential of the mosquito pathogenic fungus Culicinomyces clavisporus

Abstract

Sporulation of Culicinomyces clavisporus developed on 87–95% of first-instar Culex quinquefasciatus larvae within 5 days after exposure to the fungus in the laboratory. On these larvae the most frequent site of sporulation was the posterior abdominal segments. Conidia remained on the cadavers for at least 3 weeks and after this time their viability was 70–90%. Spore production on cadavers selected with sporulation on the entire cuticle of the thorax and abdomen was 7.4 × 10 4 conidia per first-instar larva and 9.4 × 10 5 conidia per fourth-instar larva. However, this degree of sporulation was only obtained in 11.2% of infected first-instar larvae in these experiments. With unselected first-instar larvae chosen at random from test trays spore production was 2.9 × 10 4 conidia per larva when the test inoculum was applied at a concentration of 10 3 conidia/ml and 5.9 × 10 3 conidia per larva when the test inoculum was 10 6 conidia/ml. Comparative bioassays showed that conidia produced in vivo were more potent than those produced in vitro in four out of six assays using Aedes aegypti larvae as test insects.