Synthesis and fungicidal activity of ethaboxam against Oomycetes

This study describes the chemical synthesis and intrinsic fungicidal activity of ethaboxam [(RS)-N-(-cyano-2-thenyl)-4-ethyl-2-(ethylamino)-1,3-thiazole-5-carboxamide], a new Oomycetes fungicide. In in vitro tests, ethaboxam showed inhibitory activity against isolates of Phytophthora and some Pythium spp, with MIC values ranging from 0.1 to 0.5 mg litre-1 for nine isolates of Phytophthora infestans (Montagne) de Bary and from 1.0 to 5.0 mg litre-1 for eight isolates of Phytophthora capsici Leonian. In tests to determine time and concentration for complete inactivation of each pathogen (five isolates of P infestans and five isolates of P capsici), ethaboxam inactivated all isolates of P infestans within 48 h at 10 mg litre-1 and those of P capsici within 96 h at 10 mg litre-1. Ethaboxam effectively suppressed development of tomato late blight caused by P infestans and pepper Phytophthora blight caused by P capsici in the studies conducted to determine its preventive, curative, persistent and systemic activity. These results show that ethaboxam has desirable fungicidal characteristics as an Oomycetes fungicide.