A SURVEY OF HEART ROT IN SOME PLANTATIONS OF ACACIA MANGIUM IN SABAH

Abstract

The extent of heart rot in Acacia mangium, was determined by destructively sampling 100 trees from 3-y-old thinnings and 195 trees varying from six to nine years old in 20 selected plots. Only 4% of the thinnings had heart rot which appeared to originate from thinning wounds. In the older trees, the average incidence of heart rot was 35.5%. The volume of wood affected by heart rot and discoloration ranged between 0.3 and 24.0% while the volume of wood affected by heart rot alone ranged between 0.03 and 18.0%. The main infection courts were dead branches while cankers and less frequently, roots and branch stubs were supplementary infection courts. There was no significant difference (p<0.05) in diameter and height of heart rotted and non-heart rotted trees. However, there was a significantly higher incidence of heart rot in 8-'y-old trees from Keningau (48.7%) than those from Kudat (10%) (p<0.05) and this was probably related to site factors. Only 4% of sampled trees were attacked by termites.