A method for controlling phytopathogen Fusarium verticillioides for substantially preventing stalk and ear rot disease of maize comprising applying crude mono-rhamnolipid biosurfactant obtained from the bacterial strain Pseudomonas aeruginosa SS14, in concentrations varying between 50 µg ml-1 and 200 µg ml-1 by weight, for soaking seeds of maize prior to sowing for growing in field conditions of light, temperature and humidity for a suitable duration to substantially inhibit growth of phytopathogen Fusarium verticillioides, the causal organism responsible for stalk and ear rot disease of maize, thereby substantially preventing stalk and ear rot disease of maize. FIG 3
