Ag nanoparticles were formed in situ in starch by redn. of AgNO3 with NaBH4 at 20 degrees C, studied for surface tension and contact angle in aq. solns. and used for controlling Bipolaris sorokiniana (Sacc.) and Pyrenophora teres (Died.) Drechs. The fungicidic activity of Ag nanoparticles was lower than that of epoxiconazole and azoxystrobin used as chem. fungicides in field crops.