Comparative fungitoxicity of the insecticide permethrin and ten degradation products

The toxic effects of permethrin and ten of its degradation products on the growth of ten fungi were determined. Permethrin was relativelynon‐toxic, with an EC50 of > 100 mg litre−1 but six of the degradation products were significantly (P= 0.05) more inhibitory. The ester hydrolysis products, 3‐phenoxybenzyl alcohol and 3‐(2,2‐dichlorovinyl)‐2,2‐dimethylcyclopropanecarboxylic acid, had EC50 values ranging from 8 to > 100 and 20 to > 50 mg litre−1, respectively. Other degradation products that were more toxic than permethrin included 3‐phenoxybenzaldehyde and 3‐phenoxybenzoic acid, with EC50 values as low as < 1 mg lite−1. Hydroxylated and substituted‐benzene metabolites were non‐toxic. Combinations of selected test compounds yielded both synergistic, antagonistic and additive interaction responses, depending upon the test system employed.