Effects of Defoliation on Coconut Yields in Papua New Guinea.

Abstract

Damage caused by defoliating insects to coconut palms was simulated,by removal of 0, 10, 20, 30, 40, 50, 60 and 70 per cent of the frond area; each treatment was replicated 10 times. This level of defojiation was maintained for 12 months by rem oval of leaf area o f new fronds to the predetermined level. Yields of nuts produced after 9 months defoliation decreased linearly with increasing defoliation. The causes of the reduction in total nuts were an accelerated shedding of nuts already on the tree at the commencement of defoliation, and premature nut fall during growth of a new crop. After 9 months defoliation, the number of fronds produced by the 70% treatment palms was significantly reduced. There was no evidence of compensatory frond growth in any treatment. Significant yield differences were detected in the 50% and 60% treatment pal ms until 5 months after defoliation ceased, and in the 70% treatment palms 17 months after cessation of defoliation. It is concluded that defoliation above 40% has long term effects on the health of the tree.