Laboratory Evaluation of the Fungus Culicinomyces Clavosporus for Control of Blackfly (Diptera: Simuliidae) Larvae

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Environmental Entomology





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Comparative bioassay experiments based on 4-day exposure of mid-ins tar test larvae to conidia showed that the original isolates of the Australian and U. S. strains of Culicinomyces s clavosporus were less active against the blackflies Simulium pictipes and Simulium vittatum (with LC50s ranging from 1.9 ×104 to 1.1 × 105 conidia per ml) than against the mosquito Aedes aegypti (with LC50s between 2.1 × 102 and 3.9 × 103 conidia per ml). The activity of the “Knight” isolate of the U.S. strain was within the same range as the other isolates when assayed against A. aegypti, but it was even less active than the others when assayed against S. vittatum. To simulate natural stream conditions, larvae of S. vittatum were exposed to the Australian strain for shorter time intervals in troughs of running water. Concentrations of 2.9 × 105 to 8.3 × 105 conidia per ml for 1- and 24-h exposure times produced 90 to 100% mortality of test larvae after a 7-day holding period, whereas a 15-min exposure to 8.0 × 105 to 1.1 × 106 conidia per ml resulted in 65 to 70% mortality of test larvae after 7 days. On the basis of these results, it appears that the existing isolates of Culicinomyces are not sufficiently active against simuliid larvae to merit serious consideration as potential blackfly control agents.

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