A review of relationships between shade types and cocoa pest and disease problems in Papua New Guinea.

Abstract

In Papua New Guinea, unlike most other cocoa cultivating countries, the permanent overhead shade is provided mainly by coconuts and/or Leucaena leucocephala (Lam.) De Wit. Selection of cocoa shade species has been based on agronomic characteristics and there have been few attempts to determine the relationships between cocoa pests and diseases and the shade species. This paper outlines the major pests and diseases in Papua New Guinea cocoa plantings and reviews their relationships to the main shade trees used. Evidence is
presented to show that many of the present day problems have arisen from the use of leucaena as a shade tree. In contrast, the widespread practice of interplanting cocoa under coconut palms has considerable economic and managerial advantages and the cocoa generally suffers less from insect and disease attack than sole planted cocoa. It is concluded that recommendations incorporating the planting of high yielding, disease resistant cocoa under high yielding, hybrid coconut palms at least three to four years old, should be formulated and actively promoted in Papua New Guinea.