Comparison of cuprous oxide and metalaxyl with mixtures of these fungicides for thecontrol of Phytophthora pod rot of cocoa

Experiments were conducted using small-scale, detached pod evaluation methods to compare the likely effectiveness in controlling black pod of cuprous oxide-metalaxyl mixtures with these fungicides alone at approximately equivalent cost doses. All fungicide treatments were about equally effective and persistent except when rain fell soon afterspraying. Treatments containing cuprous oxide then gave very poor control of artificialinoculations with Phytophthora palmivora zoospores . Further laboratory' scale tests confirmed that cuprous oxide was readily leached by washing before the deposit completely dried whereas metalaxyl was very rapidly adsorbed on to ihe pods. A black pod control strategy is proposed using metalaxyi during critical wet periods and cuprous oxide for the rest of the year to reduce the possibility of metalaxyl resistance becoming apractical problem.