COMPARISON OF METALAXYL CUPROUS-OXIDE SPRAYS AND POTASSIUM PHOSPHONATE AS SPRAYS AND TRUNK INJECTIONS FOR CONTROL OF PHYTOPHTHORA-PALMIVORA POD ROT AND CANKER OF COCOA

Field trials evaluating potassium phosphonate foliar sprays and trunk injection for control of Phytophthora palmivora pod rot and canker of cocoa (Theobroma cacao L.), were conducted over two years at six commercial plantations and at the Papua New Guinea Cocoa and Coconut Research Institute, Keravat. Over a wide range of management inputs and environmental conditions, trunk injection of potassium phosphonate gave control of Phytophthora palmivora pod rot comparable to that obtained with conventional metalaxyl/cuprous oxide pod sprays. Significant reductions in pod rot incidence were obtained at five of the six plantations. Injection gave improved control of stem and branch cankers, resulting in negligible incidence at some sites. Potassium phosphonate foliar sprays gave poor control of both canker and pod rot and were less effective than either trunk injection or metalaxyl/cuprous oxide sprays.