Studies on synergistic toxic effects of copper and dithiocarbamate pesticides with the ciliate protozoan Colpidium campylum (Stokes).

The toxicity of seven dithiocarbamates and interactions occurring with copper were studied with the ciliate protozoan Colpidium campylum. No product was toxic at 0.1 mg liter-1. Thiram and mancozeb are the most toxic products (lethal at 1 mg liter-1) and ziram and propineb the least toxic. Concerning interactions with copper, no or slight interactions were observed with propineb and mancozeb, although a strong synergistic toxic effect was observed in a previous work with two structurally related products, maneb and zineb. On the contrary, the responses observed with alkyl-related dithiocarbamates (ferbam and ziram) and ethylene bis-related dithiocarbamates (nabam, thiram, and metiram) are in correlation with the results known in the literature. The synergistic toxic effect of copper and dithiocarbamates thus seems to be related mainly to the alkyl- or the ethylene bis-dithiocarbamate structure, but is not constant for molecules associated with metals (propineb, mancozeb, maneb, and zineb).