Control of cucumber downy mildew with novel fungicidal mixtures of Oxathiapiprolin

The efficacy of four oxathiapiprolin (OXPT)-based, novel fungicidal mixtures against downy mildew in cucumber caused by Pseudoperonospora cubensis was examined in growth chambers. OXPT+chlorothalonil (CHT) mixed at weight ratio of 1 + 66.7; OXPT+ azoxystrobin (AZ) 1 + 10.3; OXPT+mandipropamid (MPD) 1 + 8.3; and OXPT+mefenoxam (MFX) 1 + 3, were compared with each other and with individual components. Mixtures performed better than all fungicides alone except for oxathiapiprolin. Of the four mixtures, OXPT+MFX outperformed the other treatments with the highest preventive, curative, translaminar, root treatment and seed treatment efficacies. Deployment in the field of such mixtures with reduced doses of oxathiapiprolin may lower the selection pressure imposed on P. cubensis and delay the buildup of subpopulations resistant to oxathiapiprolin.