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Disease Control and Pest Management

Synergy Between Metalaxyl and Mancozeb in Controlling Downy Mildew in Cucumbers. Yair Samoucha, Graduate student, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel 55210; Yigal Cohen, professor, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel 55210. Phytopathology 74:1434-1437. Accepted for publication 30 April 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1434.

A single foliar spray of either metalaxyl, mancozeb, or a mixture of both was applied to cucumber plants in growth chambers or in the field 1 day before inoculating with metalaxyl-sensitive or metalaxyl-resistant strains of Pseudoperonospora cubensis. Disease records taken at 7 days after inoculation showed a greater efficacy of mixtures over that of each fungicide separately at corresponding concentrations. Synergy factor values (the relative increase in control efficacy) obtained for the metalaxyl-sensitive and -resistant strains in growth chambers were 1.09- 1.36 and 1.12- 2.90, and in the field 1.06- 1.36 and 2.66- 24.41, respectively.