The present invention includes compositions and methods of for treating plants infected with fungal pathogens by contacting an infected plant or plant at risk of infection with a fungicidal composition comprising an fungicide selected from copper compound such as copper octanoate or copper hydroxide, or a triazole fungicide such as myclobutanil, propiconazole, tebuconazole or epoxiconazole, an enhancer selected from apyrase inhibitors, e.g., N-(m-tolyl)-[l, l'-biphenyl]-4-sulfonamide, S-heptyl 2-oxo-2H-chromene-3-carbothioate, 3-(N-(4-bromophenyl) sulfamoyl)-N-(3-nitrophenyl) benzamide, or (E)-3-methyl-N'-(l-(naphthalen-2-yl) ethylidene) benzohydrazide and, optionally, a phytologically-acceptable inert carrier.