Abstract
The objective of this investigation was to determine the impacts of fungicide, insecticide, plant growth hormone (gibberellic acid) on soil microbiota, and the growth characteristics of Aspergillus flavus. In the fungicide or insecticide mixed with plant growth hormone treated soil sample, the total viable number of soil microbiota was found to be higher than that of the soil treated with fungicide or insecticide alone. Moderate effect of insecticide used on the total number of fungi was observed. On the other hand the effect of insecticide on soil bacteria was more than effect of fungicide, and the negative effect of fungicide on soil bacteria was observed particularly at latent periods (15 and 20days) of application. A great sensitivity to fungicide and insecticide was observed in the case of nitrogen fixing bacteria. At 15days after fungicide and insecticide application the adverse effect was found. Morphological deformations were clear in A. flavus cultivated on medium containing fungicide, the fungus failed to form conidiospores, conidiophores and vesicles. Intermediate and terminal outgrowths like blisters and terminal vesicle originate from hyphae. The addition of plant growth hormone reduced the effect of fungicide on fungus.