ABSTRACT: A short-term (48 h) chemical toxicity test using larvae of the coot clam Mulinialateralis was modified to evaluate potential toxicity and pathogenicity of microbial pest control agents. M. lateralis larvae, at the straight-hinged stage of development, were exposed to various microbial pest control agents including: a mosquito larvacide, Bacillus thuringiensis var. israelensis (Bti); a molluscicidal strain of Bacillusalvei; a viral pathogen of the gypsy moth Lymantriadispar nuclear polyhedrosis virus (LdNPV); and a broad host-range fungal insect pathogen, Metarhiziumanisopliae. Mortalities significantly higher than heat-killed controls were obtained with Bti at a 10^-4 dilution of a commercial preparation, and with LdNPV at an occlusion body density of 1 x 10⁶ ml^-1. Sodium dodecyl sulfate (SDS) and the water-soluble fraction of No. 2 fuel oil (WSF_oil) were also tested to provide a measure of comparison, sensitivity and precision. SDS, toxic at an LC₅₀ of 6.3 mg l^-1, had a mean coefficient of variation of 23%. The clam larval toxicity test was very sensitive to WSF_oil; exposures resulted in an LC₅₀ of <10% v/v. Because of its precision, sensitivity and simplicity, the M. lateralis larval test has the potential to be useful for assessing adverse effects that microbial pest control agents may have on nontarget bivalves.

KEY WORDS: Biological control · Nontarget effects · Mulinia lateralis

Published in DAO Vol. 26, No. 3 (1996) on September 12
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1996