Trianthema portulacastrum L., a member of aizoaceae is indigenous to South Africa but is widely distributed in tropical and subtropical areas as a noxious weed. The mycoflora namely Alternaria alternata (Fr.) Keissler., Colletotrichum capsici (Syd.) E.J. Butler & Bisby., Bipolaris maydis (Y.Nisik. & C.Miyake) Shoemaker., Curvularia lunata (Wakker) Boedijin., Curvularia tuberculata Sivan. and Gibbago trianthemae E.G. Simmons was isolated from highly infected portions of the weed. The pathogenesis of fungal isolates was confirmed by Koch’s postulates primarily and the host specificity of the isolates was evaluated on green house plants by spore treatment. Among the isolates, Gibbago trianthemae was highly aggressive to weed and it was considered as potential biocontrol agent (Mycoherbicidal agent).