After 1, 10, 15 and 20 days of pesticide application at field rates in treated and control soils, the total numbers of microorganisms were counted. The numbers of colony forming units (CFU) in the selective media were determined by means of the serial dilution technique and the spread plate method. Viable counts for fungi were performed using rose bengal-streptomycin agar containing (per liter): 10 g glucose; 5 g peptone;1 g K2HPO4; 0.5 g MgSO4 · 7H2O; 0.033 g rose bengal; 15 g agar. Streptomycin was added after autoclaving at final concentration of 30 mg ml. The plates were incubated at 28 C and colonies were counted after 5 days. Analyses were performed in three replicates.