Field Control of Potato Late Blight by Synergistic Fungicidal Mixtures. Yair Samoucha, Research Associate, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel. Yigal Cohen, Professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan 52100, Israel. Plant Dis. 73:751-753. Accepted for publication 13 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0751.

Five fungicides and six fungicidal mixtures were compared on field-grown potatoes (cv. Alpha) for the control of phenylamide-sensitive and phenylamide-resistant field isolates of Phytophthora infestans. Fungicidal mixtures were far more effective in controlling both isolates than the fungicides applied singly. The mixture of mancozeb and cymoxanil (Mancur) and mixtures of mancozeb, cymoxanil, and oxadixyl (Pulsan and Sandocur-M) were highly effective and synergistic in controlling the phenylamide-resistant isolate of the late blight fungus. The cymoxanil mixtures may be suitable for late blight control in areas of Israel where phenylamide-resistant populations of P. infestans prevail.

Keyword(s): phenylamide resistance, chemical control, fungicide interaction, acylalanines.