6.1 Pests

I. Insects
II. Mammals
III. Minor Insects

Insects

1. Termites

It damages the husk of the coconut plant initially and the base subsequently. When the nut is examined the damage to the husk will be visible. The withering of the shoot also could be seen. When the withered shoot is pulled by hand it will easily come out.

Control

If the damage by termites is minimum it has to be removed and for chemical treatment, 1-2 mls of “Itdakloprid 20% “ dissolved in 1L of water and the plant should be submerged for about 3 minutes.

2. Plesispa 

This attacks plants up to 5 years of age. The insect lives in the unopened long leaves. Long lines and spots will get visible and become brown-coloured and dried up later.

Control

Chemical treatment is injecting into the shoot Carbosalfan 3ml diluted in I L of water.

3. Black beetles

Here the shoot shall get seriously damaged resulting in withering of the growth and delay in flowering. The area of the shoot shall get damaged and if the small plants get attacked the shoots shall get withered away or become crooked.

Control

It is important to maintain the cleanliness of the land. Beetles lay eggs on organic matter, hence coconut trunks, cow dung, and rubbish heaps must be removed.

Keeping two camphor balls on fronds closer to the shoot and applying burnt engine oil on the fronds surrounding the shoot. Placing of pheromone traps purchased through the Coconut Development Officer of the area.

4. Red beetles

This is the death knell of the coconut plantations and coconut trees of 3 to 10 years of age get affected. The eggs are laid in the cracks of the trunk, soft roots, damaged etc. The worm gets out of the egg gets into the trunk and attacks the internal tissues resulting fall of the tree either at the shoot or at the base.

* Holes in the tree
* Visibility of essence near holes
* Fronds becoming pale yellow
* Withering of the shoot
* Hearing of sounds when the ear is placed onto the trunk

Control

One of the following methods can be used for Control

* To check carefully the trees available, between 3 to 10 years of age
* To cover big holes using cement
* When branches are cut off to leave about three feet and applying burnt engine liquid tar oil
* To close the holes at the bottom of the tree with soil.
* Removing damaged trees, cutting into small pieces and burning them down.

Recommended chemicals

I. Monocrotopose

40 ml injected into the matured tree trunk by using an auger

II. Penthoyite 500 EC

Divide into 3 equal portions 40ml. Drill three holes of equal height 6” above the damaged area and apply the portions.

III. Vertaco

Dissolving 40g in 250ml of water and injecting through two holes made 1-2 feet of height. For each hole, 30ml has to be injected. Syringes must be used and after 3 days holes must be covered using cement.

Additionally through the Coconut Development officer of the Area, advice on Red Beatles pheromone traps and instructions and use in the field.

5. Mite

This has become a major crisis for the coconut plantations on the island. Small tender coconuts get damaged through this. Mites live about three months feeding on the soft cells of the small tender coconuts.

When observed a yellow-coloured triangular spot appears and it grows gradually and becomes brown-coloured, resulting in:

* Falling off nuts
* Smaller nuts

Control

* Using Sulphur- Palm oil mixture Sulphur and (add the method of making the mixture)- How to make the mixture: to 800 ml of water add and mix soap powder 12 gms and sulphur 5 gms well and add palm oil 200 ml)
* Using natural enemies of pests

Mammals

When considering the coconut plantations, this damage too is substantial. The damage is more during the plant stage and when bearing nuts.

* Wild boar
* Wild rat
* Porcupine
* Ape
* Monkey
* Elephants
* Giant Squirrels

Control

* Surrounding plants with barrels
* Fixing poles and tying those with plastic sheets
* Using tyres filled with soil
* Planting glydisira
* Using firecrackers

Minor Insects

1.Yellow-spotted locust – Aularchesmiliarris

Characteristics

The first record that the yellow-spotted locust damages the vegetation was in 1947. This pest had been seen in many parts of the Island and records indicate its population had heavily increased in many instances. Female pupa makes a hole in the soil and lays eggs about 3-4 inches below the ground in cluster form. Each cluster may carry 15-60 eggs. It creates a cover with phlegm to protect the eggs. Laying of eggs takes place mostly in October and November it selects areas well covered under large trees. The insects coming out of the eggs are brown in colour. Within 1-2 days those will become black in colour and yellow coloured lines could be seen along the bodies. There will be 6 stages of larvae of the yellow-spotted locusts and it will take 5-6 months to complete the larva stage. This pest lives in groups and each group will have 3000-4000 or more. The locust is about 1 ½ inches in length and a grown locust will be about 5 c.m. (2 inches). Its head and antennas are black in colour.

Damage and how to recognize

It eats the leaves of the coconut trees.

Control

⦿ A collective effort is needed to control the yellow spotted locusts and should be vigilant for their arrival. During the months of October and November, those will arrive under the shade of large trees and it is possible to collect them with hands and destroy them. At this stage, the pupas are not active and they could be collected with hands.

⦿ Through identifying the doubtful areas where the pupas have laid eggs and turning the soil and exposing the clusters of eggs to sunshine and allowing the birds (especially mynahs), ants to eat in order to destroy.

⦿ Make a mixture with 2 litres of water, 10 m.l. of kerosene and 10g of soap in a bucket and collect the pupas into the bucket. As the pupas are dormant in the morning due to low temperatures collecting those has to be done in the morning hours.

⦿ When the damages are acute spray carbosulfan 3m.l. mixed with 1 litre of water.

2. Coconut scale

Characteristics

Coconut scale is a species that destroys coconut leaves in all areas where coconuts are planted in Sri Lanka. Since the dry season is conducive to their growth, during long droughts these pests could be seen often. Their population will decrease during the rainy season. These pests sucking the juices under the coconut leaves could be seen by using a magnifying glass. The centre of these pests is yellow in colour and surrounded by a transparent cover similar to a fried egg (bull’s eye).

Damage and how to recognize

Affected coconut trees could be easily identified by the small yellow coloured spots on the coconut leaves. When examine under the leaves these pests could be detected. Those are yellowish-white in colour. When the affected areas of the leaf are scratched with a fingernail there will be wetness with moisture if the live pests are available, if the pests are dead there will be a dried powdery feeling to the touch and scales will get gathered around the end of the fingernail. When the pest population is heavy the whole coconut branch will become yellow in colour and get dried up. At this stage, it can damage the flowers and small very tender fruits. When the plants get damaged their growth will be affected.

Control

⦿ Agronomical methods – If the damage is seen only on a few fronds those could be cut off and burnt. If the damage is detected on the small plants those leaves could be cut off or crushed by hand.

⦿ Biocontrol methods – Ladybird insects are natural predators capable of controlling these pests. There are two varieties – one is known as “Chilocorus nigritus” – a round-shaped insect of a size of a pepper seed and the other is “Pallas sirumpilinus” which is slightly smaller than the previous one. Its worms are white in colour and spread similar to the shape of fingers on its body. Both these varieties are greedy eaters and could successfully control the damage by coconut scales

⦿ Chemical methods- These methods should be considered only if the bio-controlling methods had not been successful in controlling the pests. The advice of the coconut development officer of the area has to be obtained. A mixture of 20-40 ml of dimethoate 40% and hoklopairofos 40% mixed with 10 litres of water has to be sprayed on the plants using a knapsack sprayer. For grown-up trees 8 m.l. of Monocrotophos 60% can be injected into the trunk.

3. Nettle caterpillar

Characteristics

This caterpillar is known as a pest that damages severely the coconut leaves in the coconut plantations in the dry zone which had not come to much attention. This pest damages the growth in all stages from the nursery to the grown trees. At the grown stage the pest is a moth and both sides of its head are light green and its wings are light brown in colour.

Damage and how to recognize

Dark brown patches could be seen underneath the coconut leaves. When the caterpillars gradually grow they destroy all the leaves leaving only the ankles. As they like well-matured leaves there is a tendency to gradually damage from the lower branches to the upper branches.

Control

⦿ If the damage is for 50 or fewer trees the lower branches could be cut off using a picker and burnt down.

⦿ The parasite “Apantalis Parase” is used as a natural predator. Its behaviour depends on the weather patterns. Instructions must be obtained from the Coconut Development officer.

⦿ Only when the effectiveness of the parasite is not satisfactory, it is recommended to use pesticides. 8 m.l. of Monocrotophos 60% to be injected into the trunks.

4. Eliminus Hypermestra

Characteristics

This caterpillar damages the plants in the nursery and the coconut plants.

Damage and how to recognize

⦿ Small leaves are eaten as cut by a small pair of scissors.

Control

⦿ Destroying the caterpillars after collecting them by hand. Spraying a mixture of carbosulfan 3 m.l. in 1 litre of water

6.2. Diseases

i. Oozing out the sap from the bark
ii. Rotting and Withering of leaves
iii. Rotting the shoot (Bud Rot)

1. Oozing out the sap from the bark

Description

Oozing juices out of the coconut trees is a common occurrence. However, if the tree is infected with the fungus “Cerosistas Paradoxa” treatment must be done to control the disease.

Damage and how to recognize

⦿ The main symptom is oozing out red-brownish sap out of the length-wise cracks on the bark. The oozing-out spaces will gradually become brownish and finally turned into a colour of blackish

⦿ Tissues under the bark where the sap is oozing out will turn yellowish and later will become brownish and get rotten away. Finally, the whole area will get decayed leaving out only the fibre. Places, where the sap oozes out, will gather together and form large oozing-out areas. After some time oozing will stop and the sap will get thickened and become like gum.

⦿ This could be seen in the trees infected with the “Ganodarma” fungus. It is very seldom such infected trees available in Sri Lanka and the special feature is forming mushrooms on the trunk closer to the ground level.

⦿ Due to burning of fire; lightning; red beetle damages; excessive usage of chemical fertilizer; floods and frequent changes of water levels the oozing out of sap could take place. It is easier to identify the trees affected by burning fire and lightning.

Remedy

⦿ Sick yellowish parts of the bark should be cut and removed by a sharp knife, a chisel or a hand adze. Till the healthy light red coloured tissue appears, sickly tissues must be removed. The parts removed must be burned down. “Bordeaux mixtures” or a fungus remover containing copper must be applied on the scratched-out parts (wounds). If a fungus remover with copper is used the quantity
has to be according to the instructions given in the label. After leaving for a few days to get dried up, the Bordeaux mixture must be re-applied.

⦿ After about 10 days, if the malady has not spread to other parts or the oozing is not visible, liquid tar is to be applied to the scratches (wounds). If it is difficult for cultivators to make the Bordeaux mixture, after cleaning off the oozing-out sections liquid tar could be applied.

2. Rotting and Withering of leaves (Weligama Coconut Leaf Wilt Disease)

Description

A Disease known as Weligama withering and rotting of leaves was found in 2000 in the Southern Province. Now it has spread over the entire Matara district and in several divisional secretariats in Galle and Hambanthota districts. This disease was reckoned as an incurable pathogenic to “phytoplasma”. Through the gazette notification 1542/7 of March 24 2008 issued under the No. 35 of 1999 Act of Protection of Trees, it has been published this malady is a pandemic. In order to control the spread a buffer zone is an area without the disease.

Damage and how to recognize

⦿ Forming of brown patches due to getting wet with water on the young fronds

⦿ Leaves getting attached to the shoot

⦿ Branches getting rotten and becoming blackish and looking as “fishing rods”

⦿ Leaves not rotted being in green colour but the ends getting blackish and shrinking

⦿ Uppermost part of three getting shrunk

⦿ The trunk getting thinner

These are the main symptoms of this disease.

⦿ Leaves getting flat and bent like ribs

⦿ Yellowing of the lower branches

⦿ Occasionally yellowing the middle branches

⦿ Getting the edges of the leaves got yellow coloured Dried up

Are the symptoms of the disease of Weligama withering of leaves.

Remedy

⦿ Tebukonosol – polikar / orayis and hexakonasol – shakthi/ kantap are the recommended fungus removers. Polikar / orayis 10 ml should be mixed with 1 litre of water. Shakthi / kantap 10 ml should be mixed with 1 litre of water. When fungus-removing mixtures are made plastic utensils must be used. Must cut off the parts of the tender coconut frond after climbing to the uppermost part of the tree. 3-4 branches closer to the shoot and the leaves that got rotten must be cut off. About 1 litre of the fungus remover must be poured into the shoot. The cut and removed parts along with the rotten ones should be burnt down. Later on, when the fungus remover is used it is not necessary to remove the rotten parts. But the new shoot must be widened and fungus remover must be poured in to get the shoot properly wet. This has to be continued for 3-4 months except during the rainy season. It is important to have a piece of proper knowledge of using fungus removers.

3. Rotting the shoot (Bud Rot)

Description

This is due to a fungus called “phytophthora palmivora”.

Damage and how to recognize

⦿ This disease is most prevalent among trees less than 45 years of age. The initial symptom is the fading of colour of the tender frond and getting withered. After that, it will become brownish and dried up.

⦿ The infected branch easily comes out when pulled. There will be an acute odour.

⦿ The healthy branches closer to the tender branch, though green in colour, will get dried up one by one. Finally, the shoot and dried-up branches will wither away and fall down.

Remedy

When the disease is identified in the first instance it could be controlled by recommended treatment.

⦿ The infected shoot has to be cut off and fungus remover with copper 1% or a fungus remover containing metalaxyl 4g s mixed with 1 litre of water should be used to wash well the shoot twice a week.

⦿ To save the surrounding trees dithiocarbamate 6g s or metalaxyl 4g s dissolved in 1 litre of water and with the mixture wash the shoots well once in three weeks during the rainy season

⦿ Furthermore, by managing properly the nutrition the strength of the trees could be maintained. For this purpose, it is important to use a balanced fertilizer mixture.

N:B: It is not possible to save the trees acutely affected by the disease. It is very important to burn down such trees. Through this step getting healthy trees infected as well as increasing the germs in the affected trees could be controlled.