Oxalic Acid Production and Mycelial Biomass Yield of Sclerotinia minor for the Formulation Enhancement of a Granular Turf Bioherbicide

The fungus Sclerotinia minor is presently under development in this laboratory as a granular bioherbicide for broadleaf weed species. With a view to enhancing the virulence of the fungus, the effect of increasing endogenous oxalic acid concentration through modification of the growth conditions was investigated. S. minor was grown in 125 ml of eight different liquid culture media in shake flasks incubated at 20°C for 7 days. The final pH, mycelial dry weight, and oxalic acid content of the spent growth media were determined and the virulence of S. minor grown on each solid culture medium was screened on detached dandelion leaves. A 330% increase in oxalic acid was obtained plus 56 mM of sodium succinate to Modified Richard's solution (MRS) as compared to MRS alone. A concomitant increase in virulence of 218% was expressed as increased lesion diameter.