A process for producing herbicides from a fungus Alternaria alteranata f.sp. lantanae deposited as a pure culture as MTCC 5432 and ITCC-4896, comprising culturing the fungus in a liquid broth; subjecting the broth to the step of filtration to separate the broth containing phytotoxins from mycelium; extracting the phytotoxins from said broth to obtain the phytotoxins; and subjecting the phytotoxins to chemical characterization.