Population Dynamics ofPhytophthora parasitica,the Cause of Root and Crown Rot ofCatharanthus roseus,in Relation to Fungicide Use

Populations of Phytophthora parasitica from the root zones of container-grown Catharanrhus raseus treated with fosetyl-Al applied as foliar sprays or soil drenches and metalaxyl applied as soil drenches were determined 3, 5, 7, 9, and 11 wk after transplanting. Fosetyl-Al had no effect on pathogen populations when applied every 4 wk as foliar sprays at either 2.4 or 4.8 g a.i./L. Pathogen populations were affected more when fosetyl-Al was applied every 4 wk as soil drenches at 1.92 than at 0.96 g a.i./L (...)