Acacia mangium Willd. - A Fast Growing Tree for Tropical Plantation

Important insect-pests

Hutacharern (1993) has described 30 insect species attacking A. mangium, together with other 48 insect species reported on A. mangium. Among theses, only a few species have profound effects. Important insect pests are root feeders (Stenocera aequisignata and termite), branch and stem borers (Synoxylon spp.), and the red coffee borer (Zeuzera coffeae). These can cause death, deformity, or reduced biomass production of A. mangium, and thus are the insects that must be carefully monitored and for which preventive measures should be employed (Hutacharern 1993).

For preventive control measures of Stenocera in the nursery isobenzan (Telodrin) application at 1.3 gallon per ha to the soils or beds or, where polythene sleeves are used, mixing the filling soil with one part isobenzan in 500 parts water before or after filling is recommended (Sharma et al. 1966). Further application ofthe chemical around the collar of each plant for two consecutive years after planting in March is required in areas with dense Sternocera populations. For controlling red coffee borer insecticides can be injected into the holes where larva pushes out their frass. To save the trees, this direct injection must be done at the earliest detection of insects (Hutacharern 1993). The adults of branch and stem borers (Synoxylon spp.) attack shoots and young stems and kill or render them to breakage. To control these insects, removing and burning broken branches in which breeding has taken place is recommended.

Important diseases

Detailed accounts of diseases of A. mangium have been given by See (1993). The common diseases of A. mangium seedlings in nursery are damping off, powdery mildew, stem galls, die-back, leaf spots, charcoal root rot disease and root knot. All these are mostly common diseases of many tree species and can be controlled by conventional nursery management techniques and prophylactic fungicidal sprays (See 1993).

Important tree diseases in plantations are root rots, heart rot, pink disease, die-back and stem canker. Root rots are caused by many fungal species like-Ganoderma spp., Phellenus spp. and Rigidoporus lignosus. Initial root rot symptoms resemble those of nutrient deficiencies. In more advanced stages when major portions of roots decayed, fallen trees or standing dead trees are good indicators of root rots (See 1993). There are no specific control measures for these diseases. Only dead and diseased trees can be destroyed to avoid spread of the disease.

The heart rot is only evident upon felling of trees because diseased trees outwardly appear healthy and vigorous. The dieback is caused probably because of combination of several factors like prolonged drought period and fungal infections. Cankers associated with decayed branch stubs and pruning wounds are good indicators of heart rot. Infected trees can continue to grow vigorously to maturity. Management options include adopting silvicultural practices that limit wounds to the stem, including early singling of multistemmed trees, short rotations and selecting provenances for slender branches and single stems. At present there are no practical measures for this disease.