EFFECT OF SOIL TREATMENT WITH THE ORGANOPHOSPHORUS INSECTICIDE PROFENFOS ON THE FUNGAL FLORA AND SOME MICROBIAL ACTIVITIES

Tests were conducted to determine the effects of Profenfos [(0-(4-brom o-2-chlorophenyl) 0-ethyl S-n-propyl-phosphorothioat] on fungal popula tions and some activities in soil. Profenfos (at 5.4 mug active ingred ient/g dry soil), has a significant adverse effect on the count of tot al fungi after 2, 4 and 6 weeks after treatment. This effect was compl etely alleviated after longer incubation. Incorporation of this insect icide into the agar medium inhibited the total count of soil fungi at 6.4 and 38.4 mug ml-1. Initial activiation followed by a decrease in C O2 output occurred in soil treated with 5.4 mug a.i./g. The two doses of Profenfos accelerated urease activity for 6 weeks after soil treatm ent, but inhibited the enzyme activity after longer periods. An inhibi tory effect on nitrate reductase activity was observed with some insec ticide treatments in the early stages of incubation followed by an act ivation in certain cases.