Metalaxyl for Control of Downy Mildew of Pea Caused by Peronospora viciae. H. Singh, Graduate Student, Department of Plant Biology, University of Newcastle upon Tyne, NE1 7RU, England. C. H. Dickinson, Senior Lecturer, Department of Plant Biology, University of Newcastle upon Tyne, NE1 7RU, England. Plant Dis. 64:1090-1092. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-1090.

Laboratory and field studies were done to evaluate metalaxyl for control of downy mildew (Peronospora viciae) of pea. Colonized areas on leaflets were smaller on plants sprayed with metalaxyl 2 days before incubation than on plants sprayed 6 days before inoculation. Similarly, areas colonized were smaller on leaflets treated 1–3 days after inoculation than on those treated 5–7 days after inoculation. Volatiles from a metalaxyl solution in a closed container prevented sporulation at concentrations of 200 µg/ml. In the field, metalaxyl at 0.01 g (a.i.)/m² in 50 ml of water (100 g [a.i.]/ha in 500 L of water) sprayed 3 days after inoculation gave best control of pea downy mildew. However, metalaxyl incorporated in soil at 2.0 kg (a.i.)/ha gave best control when applied at the same time as inoculation or 3 days later.

Keyword(s): Ridomil, volatile activity.