Abstract: Tobacco black shank caused by Phytophthora nicotianae is one of the most destructive diseases suffered by tobacco in China. Streptomycin, calcium oxide and synthetic fertilizer are three important non-target chemicals used frequently during tobacco growing period. This study has evaluated the activities of the non-target chemicals streptomycin, calcium oxide and synthetic fertilizer on the mycelial growth, sporulation, zoospore formation and germination of cystospores of P. nicotianae. Metabolic fingerprints of P. nicotianae under pressures of those three chemicals are also compared with control treatments. Streptomycin inhibited mycelial growth, sporangia production, zoospore formation and cystospore germination more effectively than the other chemicals tested. Calcium oxide inhibited sporangia production, zoospore formation and cystospore germination at much higher concentration. Mycelial growth of P. nicotianae was not affected by this chemical. Synthetic fertilizer had negative or no effect on sporangia production and no effect on mycelial growth. Zoospore formation and cystospore germination was inhibited at high concentrations of this chemical. Metabolic fingerprint of P. nicotianae was not or poorly affected by calcium oxide and synthetic fertilizer. Streptomycin significantly changed the fingerprint of the pathogen, substrate of y-aminobutyric acid, fumaric acid, L-alaninamide, L-alanyl-glycine, L-proline, L-pyroglutamic acid and putrescine cannot be utilized by P. nicotianae. So it is no use to add calcium oxide to soil for black shank management in the field, while is useful for streptomycin. Synthetic fertilizer in some case may enhance the development of the disease. These new findings provide important information for black shank management in the future.