Periodic surveys were conducted to seek potential indigenous fungal agents for development as mycoherbicides against horse purslane, a major weed of agricultural fields in India. Pathogenic fungal species were isolated and identified from naturally infected horse purslane. The biocontrol potential of these pathogens for horse purslane was evaluated by studying their host range and virulence under growth chamber and greenhouse conditions. Three candidates, Alternaria alternata, Fusarium oxysporum, and Phoma herbarum, were identified as potential candidates for biological control of horse purslane. Preliminary host-range tests and pathogenicity studies, conducted using 45 crop and weed plants belonging to 18 families, demonstrated that P. herbarum provided effective weed control and was safe to most of the plant species tested. Further mycoherbicidal application of P. herbarum as plant spray under field condition caused mortality of horse purslane 60 d after application of the inoculums. Phoma herbarum is a good mycoherbicide candidate against horse purslane.

Nomenclature: Alternaria alternata (Fr.) Keissler, Fusarium oxysporum Schltdl., Phoma herbarum Westendorp, horse purslane, Trianthema portulacastrum L. TRTPO.