Relative Toxicity of Certain Pesticides to Lagenidium giganteum (Oomycetes: Lagenidiales), a Fungal Pathogen of Mosquito Larvae1

Abstract

Laboratory experiments were conducted to determine the relative toxicity of certain insecticides, herbicides, and fungicides to the vegetative growth and zoospore production in North Carolina (NC) and Louisiana (LA) isolates of Lagenidium gigallleum. Zoospore production in both isolates was less tolerant than mycelial growth to most of the pesticides tested and, thus. the IC,,, values (inhibition concentration) for mycelial growth rate on agar underestimated toxicity. The most toxic pesticides to one or both isolates of L. giganteum were captan, gamma-SHC. DOT. toxaphene, chlorpyrifos, and fenthion. These pesticides produced at least 10% inhibition of mycelial growth rate or completely inhibited zoospore production at concentrations below 5 parts per million (ppm). The least toxic pesticides caused a 10% inhibition in mycelial growth rate and failed to inhibit zoospore production at concentrations greater that 50 ppm. These were ditlubenzuron, permethrin. temephos, and propoxur (LA isolate only). Pesticides of intermediate toxicity were: malathion, carbaryl. methoprene. alachlor, and atrazine. The two isolates differed substantially in their tolerance of the following pesticides: malathion, chlorpyrifos, toxaphene, carbaryl, propoxur, permethrin, and methoprene. At their recommended rates of application for control of mosquito larvae, methoprene, fenthion, malathion, and temephos would probably be compatible with both isolates of L. giganteum.

Variation in Resistance to Benzimidizole in Different Biocontrol Agents Based on Protein Sequence Homology

“…Benomyl, the active ingredient of the benzamidazole anthelmintics and fungicides, has been reported to be the most common inhibitor of all compounds tested against various fungi [5][6].…”