The fungus Trichoderma viride Persoon was found to effect the hydrolysis of fenitrothion (Sumithion) and fenitrooxon in pure culture. After incubation with the test compounds, liquid cultures were extracted with ethyl acetate and the extracts were analyzed by gas chromatography for residual test compounds and their hydrolysis product, 3-methyl-4-nitrophenol. A cleanup procedure, using Amberlyst A21 resin, was developed to facilitate the analysis. Evidence was found to suggest that this nitrophenol is cometabolized by the fungus.Purity of both compounds was confirmed by mass spectroscopy and proton magnetic resonance.Aminofenitrothion was prepared by zinc/hydrochloric acid reduction of fenitrothion (Sumitomo, 1977). 3-Methyl-4-amipophenol and 3-methyl-4-nitrophenol were obtained from Aldrich Chemical Co.; the former compound was used as supplied, and the latter was recrystallized (water) before use.

Microbial toxicity of triclopyr (3,5,6‐trichloropyridinyloxyacetic acid, Garlon) was measured with several microorganisms in comparison with the related herbicides 2,4‐D (2,4‐dichlorophenoxyacetic acid) and picloram (4‐amino‐3,5,6‐trichloropicolinic acid). Growth inhibition of three fungi (Trichoderma viride, Mortierella isabellina, and Saprolegnia parasitica) was measured in terms of colony size on agar plates and in terms of cell counts for two algae (Chlorella vulgaris and Chlorella pyrenoidosa). Dehydrogenase measurement by a direct 2‐(4‐lodophenyl)‐3‐(4‐nitrophenyl)‐5‐phenyl tetrazolium chloride method was used for the bacteria Pseudomonas pictorum and Arthrobacter globiformis. Dose‐response curves were determined to obtain EC50 values for triclopyr, 2,4‐D, picloram, their commonly used amine salts, and the degradation products, 3,5,6‐trichloro‐2‐pyridinol, 2,4‐dichlorophenol, and decarboxy picloram. Toxicities of triclopyr and 2,4‐D were similar in most cases, and both compounds were more toxic than picloram. The three degradation products were substantially more toxic than the respective parent compounds. The algae were most sensitive and gave much lower EC50 values than the fungi and bacteria.