Activity against plant pathogenic fungi of phomalactone isolated from Nigrospora sphaerica

Phomalactone, 5,6-dihydro-5-hydroxy-6-prop-2-enyl-2H-pyran-2-one, produced by the fungus Nigrospora sphaerica, was tested in vitro against nine plant pathogenic fungi, and specifically inhibited the mycelial growth of Phytoph thora infestans, with an MIC value of 2.5 mg litre(-1). Its inhibitory acti vities against sporangium and zoospore germination of P infestans were simi lar to those against Phytophthora capsici. In vivo, at 100 and 500 mg litre (-1), it reduced the development of tomato late blight caused by P infestan s. (C) 2001 Society of Chemical Industry.