This study is conducted at laboratories of College of Agriculture- university of Kufa in order to evaluate three algae Microcystis sp., spirulina eplatensis and sarconema sp. and their organic extracts against Rhizoctonia solani pathogen .
The antagonistic ability of Microcystis is effective against R.sloni because it gives colony diameter 7mm , with inhibitory percentage 65% , as compared with control which gives 20mm of colony diameter .The results revealed that methanol extract was more effective in reducing the viable cells of R.solani which give 28.66 x 104 CFU/ml as compared to 32.40 x 104 CFU/ml at the control .Viable cells of R.solani are reduced with the application of Microcystis which is 26.46x104 CFU/ml as compare with spirulina platensis and sarconema which give 29.18 and 28.14x 104 CFU/ml respectively .
The ethanolic extract of Microcystis sp. has the superiority of reducing colony diameter of R.solani , when gives inhibitory zone 26mm as compared with acetone as an extract of the same alga which gives inhibitory zone 20mm