Effect of insecticides on the growth and distribution of soil mycoflora in agriculture fields at narasannapeta

The pri Pesticides have become integrated into transport and degradation processes that characterize soil ecosystems. Although, pesticides are anticipated to protect crops, they may affect non-target organisms and pollute soil environment which might result in alteration in the equilibrium of soil processes for shorter or longer periods. Eleven fungal species like Aspergillus flavus, A.niger, A.oryzae, Curvularia lunata, Fusarium oxysporum, F.solani, Penicillium aurentiogriseum, P.chrysogenum, P.frequentans, Rhizopus stolonifer and Trichoderma harzianum were selected for the study. Three commercial insecticides i.e; Dimethoate, Profenofos and Chlorpyriphos were used to study their effects on soil fungi. The study was conducted to determine the effects of insecticides application on soil fungal populations, at different application rates ranging from ½litre, 1litre and with the control soil samples having no insecticide injection. A total of 282 colonies of 11 species were isolated from the control plates examined in 3 different crops (Rice, Black-Gram and Ground-Nut) of Narasannapeta Mandal, in Srikakulam District. 230 and 158 colonies were isolated from the soils treated with ½ and 1 Lt Dimethoate. From the use of Dimethoate none of the species were extinct. 215 and 144 colonies were isolated from soils treated with ½ and 1 Lt Profenofos, and finally a total of 194 and 125 colonies were obtained from soils treated with ½ and 1 Lt of Chlorpyriphos, thus confirming Chlorpyriphos as the more destructive among the insecticides used. Application of Profenofos and Chlorpyriphos yielded similar results leading to the extinction of F.oxysporum, F.solani and T.harzianum. The results revealed that insecticide applications caused reduction in microbial population present in the soils when compared with the control.