Factors likely to influence the production of Phaeoramularia sp. as a mycoherbicide to control crofton weed (Ageratina adenophora) were investigated. The fungus grew best on potato-dextrose agar (PDA) and carnation leaf-piece agar and sporulated best on PDA and a decoction agar made from A. adenophora. The fungus grew and sporulated best at 20 and 25°C and at water potentials between −0.4 and −1.5 MPa. For small scale production of conidia of the fungus a combination of submerged and solid culture with the fungus grown in liquid culture resulted in the greatest number of conidia. Comparative studies showed that mycelium was as pathogenic as conidia and that the former may have potential for further development as a mycoherbicide.