We mixed biogas slurry with 6 commercial fungicides and screened them against 11 phytopathogens. Results showed that the inhibition effect of biogas slurry was different for different pathogens, and no significant difference between treatments of Didymella bryoniae, Fusarium oxysporum f. sp. vasinfectum, Aspergillus niger, Rhizoctonia cerealis, F. graminearum, and Septoria tritici was observed. However, significant differences were found among Penicillium sp., Botrytis cinerea, Alternaria sonali, F. oxysporum f. sp. melonis, and Sclerotinia sclerotiorum. The approach described here presents a promising alternative to current manipulation, although some issues still need further examination. Information obtained from this study could contribute to better utilization of biogas slurry and sustainable agriculture.