Assessment of sanitation and fungicide application directed at cocoa tree trunks for the control of Phytophthora black pod infections in pods growing in the canopy

摘要

Studies were conducted in two cocoa-growing areas of Ghana, one solely affected by Phytophthora palmivora and the other predominantly by Phytophthora megakarya, to determine the effectiveness of sanitation practices and fungicide application on tree trunks for the control of black pod disease in the canopy. Sanitation practices including weeding, pruning, thinning, shade reduction and removal of mummified pods were carried out prior to fungicide applications, and diseased pods were routinely removed at monthly intervals during harvesting. Three types of fungicides were used: systemic (Foli-R-Fos 400) applied as injection into the main trunks, semi-systemic (Ridomil 72 plus) and contact (Nordox 75, Kocide 101, Kocide DF, Blue Shield and Funguran-OH) applied as sprays onto pods on the main trunk. Sanitation combined with fungicide application on the trunk significantly reduced black pod disease incidence in the tree canopy. For fungicides applied as a spray, Ridomil 72 plus at 3.3 g l?1 and Kocide DF at 10 g l?1 and as injection, 40 ml Foli-R-Fos 400 injected twice a year, performed better than the other fungicide treatments. The position of pods significantly influenced the incidence of canopy black pod infection in the P. megakarya predominantly affected area but to a lesser extent in the P. palmivora solely affected area. However, no significant interactions were found between fungicide treatments and the position of pods on the tree in both disease areas. The determined trunk-canopy relationship in the development of black pod disease on cocoa can be used in disease control programmes to maximise the impact of sanitation practices, achieve judicious application of fungicides, thereby reducing the environmental impact of fungicides on the cocoa ecosystem, and ultimately increase the economic returns.