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Disease Control and Pest Management

Efficacy of Systemic and Contact Fungicide Mixtures in Controlling Late Blight in Potatoes. Yair Samoucha, Graduate student, 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. Phytopathology 76:855-859. Accepted for publication 6 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-855.

A single foliar spray of either metalaxyl, fosetyl Al, mancozeb, fentin acetate, folpet, chlorothalonil, captafol, or one of a mixture of them was applied to potted potato plants (cv. Alpha) 1 day before inoculating with either a metalaxyl-sensitive (MS) or -resistant (MR) field isolate of Phytophthora infestans. Systemic and contact fungicidal mixtures were far more effective in controlling both MS and MR isolates than individual components at corresponding concentrations combined. No such increased efficacy was exerted by mixtures of metalaxyl and fosetyl Al, nor by mixtures of mancozeb and fentin acetate. It is hypothesized that any two fungicides that differ in mode of action and in stage of fungal growth that they affect will exhibit increased control efficacy of late blight in potato.