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The epidemic of the nut infesting coconut mite (Aceria) that was first reported from Puttalam District in late 1997 is now spreading in Anuradhapura, Jaffna, Mannar and Trincomalee districts and some parts of Polonnaruwa, Kurunegala, Batticaloa and Gampaha districts.

The pest is difficult to manage by any known control measure.

Therefore, coconut growers are requested to be vigilant and inspect each of their bearing palms for the pest damage without delay.

The coconut mite is minute in size and could not be seen by naked eye. It lives beneath the perianth of nuts and feeds on the soft tissues of the outer skin of the nut. Feeding affects the growth of the developing nut.

The symptoms of the damage could be observed on nuts of any age, but initial symptoms are more prevalent in young nuts than older ones.

Initially yellowish white, triangular shape patches could be observed just below the perianth of nuts (photo), which subsequently enlarge and turn brown (photo).

If the damage is mild, the nut size will not be affected although the brownish scars are present on the nut. However, severe damage results in crop loss due to immature nut fall and smaller and deformed nuts (photo) which would not be marketable. the damage does not affect the quality of the kernel. Please note that brownish patches could occur due to damage by other mites which are not harmful, but those patches do not have a triangular shape.

If above symptoms are found growers should carry out measures recommended below:

1. If the symptoms are found only in a few palms in an area of very low pest incidence or previously unreported area effective control, particularly eradication of the pest from the area would be possible by cutting and burning all nuts except unopened inflorescence of the infested palms.

2. If a large number of palms are infested first six immature bunches should be cut and burnt.

Affected nuts in the rest of the bunches should be removed and burnt. These nuts should not be mooed to other areas and should be burnt in the vicinity of the infested palms. To avoid further infestation spray "margosa mixture" (see below) to thoroughly wet the area of the leaf axiles of the affected palms once. Inspect palms regularly and repeat above 1 and 2 if necessary.

3. If the pest damage is in a large area it is recommended to spray all affected palms with 'margosa mixture"

Ingredients: Neem oil 20 ml, garlic 20 g., soap 5 g., 11 water. Method: First dissolve soap in 100ml of lukewarm water and add neem oil. For effective results use fresh neem oil of good quality.

Crush pealed garlic, add 100ml of water and extract juice by filtering. To extract juice you may use an electric blender.

Then mix neem oil emulsion with garlic juice and add water to bring the volume up to one litre.

Application: Spray 250ml of the mixture per palm to thoroughly wet all the bunches of each affected palm. A climber could spray this mixture with the use of a hand sprayer.

For large scale spraying heavy-duty spray machines, which could be operated from the ground could be used. Spraying should be repeated 2-3 times at 1 1/2 month intervals.

Although this treatment would not control the pest completely, it will reduce the crop loss due to the pest damage. Growers are also advised to carry out the following measures to prevent further spread of the pest.

* Collect and burn all the nuts fallen due the pest damage in the estate.

* The coconut mite has been declared as a quarantine pest and transport of green nuts and green husks to uninfected areas is prohibited by law. Therefore transport of such material should be avoided as mites could be spread through this mean. The coconut mite was first recorded in Mexico in 1965 and has been reported from many other countries in the Caribbean, South America and Africa and recently from India. Despite continued attempts, no effective control strategy has been developed even by these countries.

The Coconut Research Institute is actively engaged in research to find effective insecticides/acaricides and biological control agents to manage the pest successfully. Studies so far undertaken have shown that none of the insecticides/acaricide available in the market could control the pest completely.

Further, highly toxic chemicals could not be recommended for repeated spraying of a tall tree such as coconut because it could be hazardous to the humans and environment. Although trunk injection of monocrotophos has been used in the past, it is no longer recommended because monocrotophos too has to be injected several times which leads to weakening of the trunk and that the nuts could not be consumed for a longer period.

Considering the disadvantages of toxic chemicals at present we recommend "margosa mixture" which is non toxic. Further screening of low toxic chemicals is underway.

The institute is exploring possibilities of using natural enemies such as a predatory mite and an entomopathogenic fungus for biological control of the pest. Studies are being undertaken to mass culture these natural enemies and to assess their establishment in the field.

After completion of the studies an integrated package using non toxic chemicals and natural enemies could be recommended for effective management of the coconut mite. An extensive program to provide necessary technical advice and assistance to manage the pest is being conducted by the Coconut Cultivation Board.

Further information could be obtained from the Coconut Development Officer of your area.

We expect your fullest co-operation to control this epidemic, which causes severe damage to coconut.

-Coconut Research Institute, Lunuwila.

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