Efficacy of Sprays of Fosetyl-Al and Drenches of Metalaxyl for the Control of Phytophthora Root and Crown Rot of Cherry. Anna Bielenin, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824-1312, and the Institute of Pomology and Floriculture, 96-100 Skierniewice, Poland. A. L. Jones, Department of Botany and Plant Pathology and the Pesticide Research Center, Michigan State University, East Lansing 48824-1312, and the Institute of Pomology and Floriculture, 96-100 Skierniewice, Poland. Plant Dis. 72:477-480. Accepted for publication 22 October 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0477.

A single foliar spray of 4.8 g a.i./L fosetyl-Al prevented the development of cankers on the scion and the Mahaleb rootstock of 1-yr-old Montmorency sour cherry trees wound-inoculated with Phytophthora cactorum. Sprayed trees were protected against infection for at least 7 mo. Necrosis on trees sprayed with fosetyl-Al 1 wk after inoculation was about a third the size of necrosis on control trees. Fosetyl-Al applied as a foliar spray three times on a 2-wk interval did not adequately control root rot on Mahaleb seedlings inoculated with P. megasperma, P. cryptogea, and P. cambivora isolated from cherry. Foliar sprays of fosetyl-Al and soil drenches of metalaxyl both reduced P. cactorum on seedlings growing in artificially infested potting medium. Metalaxyl applied as a soil drench (5 and 10 mg a.i. per seedling) was more effective then fosetyl-Al applied as a foliar spray in preventing mortality and root rot of Mahaleb seedlings growing in a potting medium artificially infested with P. megasperma, P. cryptogea, or P. cambivora.