Coconut caterpillar, prevalent in many coconut growing areas in Sri Lanka, is a pest that can cause severe damage to coconut plantations.
The coconut caterpillar damages the coconut tree by eating the tissues beneath the coconut leaf, the fertile parts of the leaf.
Characteristics of the damage
- Damaged areas of the coconut leaf first turn in to green colour , then gradually turn in to brown colour and finally give an appearance of being burnt.
- Places where the branches of the lower part of the coconut tree get dried up without any pattern, shall be visible.
- Due to damage to the branches, tree shall become weak and the yield shall get reduced.
- When examining the underside of the leaves, worm nests shall be visible.
Unless the damage is properly managed, the tree will die.
Life cycle of the Coconut caterpillar,
- Complete life cycle of a coconut caterpillar is between 2 – 2 1/2 months.
- During the caterpillar’s adult stage, it takes the form of a small moth. At this stage the caterpillars begin to breed by laying their eggs underneath the branches of the lower section of the tree. An adult caterpillar is about 20 millimeters (about 1 inch) in length.
- About 30-40 days after laying eggs, these larvae (caterpillars) turn into pupa. In this pupa stage it looks Light reddish brown in colour. When damaged coconut twigs are cut off and underneath is examined, pupae shall be visible in the nests made with pieces of leaves and refuse material.
- After 14 – 21 days of pupation, it reaches adult stage.
1. If a slight damage (eg. In less than 5 branches) is detected, those affected branches should be cut off along with 5 – 6 branches in the lower section of the tree and be burnt.
Cutting and burning of branches should be carried out with proper understanding and knowledge, as the caterpillars in the adult stage could fly to the trees in close vicinity. This can lead to an increase in the number of damaged trees as spawning can occur on healthy coconut trees. Hence cutting and burning of branches should be carried out in all stages of the caterpillar, except when it is in the adult stage as a moth.
2. Coconut caterpillars in the adult stage can get attracted and destroyed by lighting a fire.
3. As a biological controlling method, the parasitic insects (predators) of the coconut caterpillar in the adult stage could be used.
• Parasitic insects fall into 2 main categories,
A. Larval parasites – bracon hebetor
B. Pupal parasites –brachymeria nepenthes
• The predators should be released to the coconut trees.
• The caterpillars shall get destroyed as the predators grow in their bodies, resulting in low number of caterpillar populations.
• However, the cold weather at night, between the months of October and February, affects the breeding of predators resulting in a low growth of them. Hence, this should be taken into consideration as it will reduce the number of predators.
• The deciduous parts of the lower floor branches damaged by the coconut caterpillar can be seen leaving only decayed lines. In such a case, action should be taken to release the parasites to those lands according to the observations and conclusions of the relevant Coconut Development Officer or a person who is well versed in it. parasitic insects should be obtained from breeding centers.
• Once the parasites are released to the field, no fires should be lit.
• If identified at early stages, the control is relatively easy. Non-identification in early stages and not taking corrective measures on time, shall result in developing the situation into an acute pandemic spreading over a large area.
When the damage is acute and developed, using parasites to control shall be futile and using of chemicals shall be necessary.
4. Chemical methods
• If the coconut plants are damaged in the early stages, it is recommended to dilute 4 ml of Marshall 20 in one liter of water and spray well the underside of the leaves.
• It is recommended to inject 60% monocrotophos into the trunk; however, usage of this pesticide is restricted due to various reasons. Obtaining advice from the Coconut Development Officer under such circumstances is recommended.
Being vigilant on one’s cultivation and informing the Coconut Development Officer or relevant authorities no sooner the damage is identified, appropriate action could be taken to control the Coconut Caterpillar.