Ecology of a herbicide transformation: Synergism of two soil fungi

Experiments in nutrient solution and in sterilized soil show that the sequential transformation of N-(3,4-dichlorophenyl)-propionamide (propanil) to 3,3',4,4'-tetrachloroazobenzene and other complex residues is brought about by the synergistic interaction of two common soil fungi, Penicillium piscarium and Geotrichum candidum. The interaction benefits both organisms as the end products of the transformation sequence allow higher growth yields than either the parent herbicide or its primary cleavage product. The synergism of the two fungi prevails only in the herbicide-induced stress situation.