Aims: To find possible approaches to utilize the mechanism of oxalate degradation by Coniothyrium minitans (Cm) in controlling the plant pathogen Sclerotinia sclerotiorum (Ss). Methods and Results: Differences in oxalate degradation by different Cm strains and effects of the initial oxalate concentration, ambient pH and nutrient factors on mycelial growth and oxalate degradation by Cm were studied in shaken cultures. Results showed that two wild-type Cm strains, Chy-1 and ZS-1, did not differ in oxalate degradation in modified potato dextrose broth (mPDB) amended with oxalic acid (OA). Cm could grow in mPDB amended with sodium oxalate (SO-mPDB) at pH 6 center dot 5 or with ammonium oxalate (AO-PDB) at pH 6 center dot 2, but oxalate degradation was very low; oxalate degradation was greatly enhanced in SO- or AO-mPDB with pH being lowered to 2 center dot 8-2 center dot 9. Similarly, oxalate degradation was higher than 90% in OA-amended mPDB at pH 4 center dot 4 but was reduced to be < 22% at pH 7 center dot 0. Five carbon sources and three nitrogen sources investigated and nutrients from mycelia and sclerotia of Ss were favorable for the growth of Cm and OA degradation by Cm. Conclusions: Cm can degrade oxalate under acidic pH. Exudates from mycelia or sclerotia of Ss may serve as nutrients for Cm mycelial growth and degradation of oxalate secreted by Ss. Significance and Impact of the Study: The finding of oxalate degradation laid a foundation for mining-related genes in Cm for engineering plant resistance against Ss. Elucidation of the importance of acidic pH and nutrients from Ss in oxalate degradation by Cm will help to understand the interaction between Cm and Ss.