Stem borers are caterpillars insects from the BEETLE. Mature adult beetles will lay the eggs and hatch into larvae. Larvae dig into the trunk and takes few months to mature. The larvae will tunnel along the branch to the branches and the main stem. It emits frass through holes drilled. Effect of attack can be seen when we see the leaves and shoots become yellow and dry.
Aquilaria stem borer worm, attack may be fatal if tree is young.
The presence of these stem borers in mature Aquilaria tree should not to worry about but it gives a positive impact that will assist in the formation of agarwood in the future. However, if these stem borers attack happened in the early planting stage (<5 years), it is better taken seriously. This is because it can cause the stem broken because it is consuming the internal tissues of the tree.
Upper branch had been bored by the worm, leafs were drying. The upper stem will be cut if no hope to recover. Worker noticed the attack was too late.
Result of upper stem 2 weeks later, photo taken 28/11/12
Early notice of the attack may safe the tree from fatality. Chemical insecticide may be injected through the entry point bored by the worm.
Photo showed stem borer in position.
7-month seedling was attacked by stem borer worm, the stem was too soft to support its upper weight when i slightly twisted it and broken into 2 halves.
Earlier rectification :
Keep the ground clean, the weed should not be too dense. You will notice the frass (dropping) from the stem borer which is round and pale in colour. It looked like granular fertilizer when i first saw. Or when you see the leaves and shoots become yellow and dry. These will alert you something is out of order for further inspection.
Frass (dropping) on the ground, pale in colour.
Chemical control :
There are number of insecticide to inhibit the attack, by using syringe to inject the insecticide in dilution according to label instruction, its active ingredient are namely Carbofuran ; Fipronil ; Cypermethrin ; Emamectin benzoate ; Cartap hydroxide.
Cut and remove the affected branch, prune the stem to the nearer healthier branch. Overtime the branch will form a straight stem of the entire tree.