Stem borers are caterpillars insects from the MOTH / 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 ; Clothianidin ; monocrotophos.
Biological control :
Ants, natural predators in preying the larvae and pupae of stem borer.
Preventative countermeasure :
Stem borer control is difficult since larvae penetrate the stem and it is too late for control when the damage begins. Applying chemical pesticide is almost useless and NOT applicable to agarwood when it is meant for human consumption, whether it is for tea or oil distillation. Click “here” for further reading.
Pros and cons of stem borer infection
For a mature tree, 20cm in BHD it should be able to withstand the attack. It depends on how you want the trees to be stressed for its final harvest. Frankly speaking, i will prefer the trees to be heavily stem borer infection, i am NOT keen on liquid inoculant for fast food harvest.
If you meet someone who is prone to liquid inoculant, you will bounce to completely reverse explanation. There is no “Right ” or “wrong” in this practical approach of man-made intervene.
You must know what you want? Like i said, engaging a contractor to perform the inoculation, is like getting a prostitute for service. A contractor CAN’T satisfy all the customers requirement, he is familiar and comfortable with his own way … and without a doubt he will lead you his way. But, that might not be your direction.
Therefore, understanding the entire picture in agarwood business is important to autopilot to your direction.