Threats, Diseases and Pest
Disease & Pest
Jamaica is fortunately free from three (3) very serious cocoa diseases. These are the Swollen Shoot Disease of West Africa, the Witches’ Broom Disease of Central and South America and in some of the West Indian Islands, the Fire Blight Disease of South America and Trinidad. These diseases cause large numbers of plants to die each year.
The major diseases currently affecting cocoa in Jamaica are the Black Pod disease and the Frosty Pod Rot disease.
Black Pod Disease:
The Black Pod disease is caused by Phytophthora palmivora, a fungus and Cherelle Wilt which is a physiological complaint. Cherelle Wilt causes the drying-up of young pods up to 5 inches in length while Black Pod Disease causes a gradual rotting of pods including the beans inside them. Black Pod disease attacks cocoa especially under damp, cool, shaded conditions. Attacks may be reduced by thinning shade trees.
Other means of coping with the disease include the prompt heaping of affected pods in an open space and the use of copper fungicides for spraying. Spraying is expensive and is only worthwhile when trees produce an average of twenty pods per crop, in area where over 20% infection commonly occurs. Spraying is carried out twice in the fall crop areas, before the rainy season begins and Black Pod appears and repeated when losses become frequent.
Frosty Pod Rot Disease (FPR)
Frosty Pod Rot is a disease caused by the fungus Moniliophthora roreri. It invades growing cocoa pods damaging them and the seeds produced. The fungus originated in Western Columbia/Ecuador and has since spread throughout South America.
The recent outbreak of the disease in Jamaica started in Clarendon in 2016. Since then, the Government of Jamaica has been offering support to the sector by providing information and training to assist in combating the disease. The fungus produces billions of spores that are spread by the wind, water or by humans. The fungus can remain on clothing and other materials and equipment for up to nine (9) months.
Symptoms of FPR
Signs and symptoms only appear on the pods. The nature of the symptoms depends on the age of the pods when they are infected:
- Pods less than one (1) month old show swellings and distortions
- Pods 1-3 months old show pre-mature ripening and large brown spots
- Pods three (3) months and older become covered by thick fungal growth that forms a thick dense mat on the pod. Infected pods become heavier than healthy pods and the beans become difficult to extract.
Treatment of Infected Plants
- Spray plants once per month for two months with one per cent of copper hydroxide (available brands are Champion, Kocide, Champs and Sulcox)
- Remove all pods, from the cocoa trees \Infected pods must be removed while there is dew on the pods. The other pods can be taken from the trees anytime throughout the day
- Pods should be collected in a double, lined or meshed bag and placed in direct sunlight for two weeks to kill any active spores. After this time they can be discarded
- Pods can also be placed in a bag and buried 18 inches deep after which a compost heap can be started with it
Infected trees should be pruned regularly
How to Prevent the Spread of the Disease
To lessen the impact of the disease:
- Adhere to the guidelines given by the authorities
- Disinfect clothes and shoes if you come in contact with a contaminated area
- Do not transfer any seedling, plant or fruit from the contaminated area
- Prune plants regularly to minimise moisture and promote ventilation
Pest Affecting Cocoa Plants
Fiddlers are pest that affect the cocoa plants. There are two (2) types of Fiddlers – the large: Exophthalmus Spp and the small: Pachnaeus Spp. The legless grubs of the Fiddlers bring about the death or debility of cocoa by eating the bark around the roots of the trees. Fiddlers lay their eggs between two leaves of cocoa trees. Grubs hatch and drop from shade trees in cocoa fields or, are blown from surrounding trees into cocoa fields.
Treatment Application for Fiddlers
Dieldrin powder applied at the rate of 2 lbs. per acre in 112 gallons of water under the canopy of cocoa trees, using a watering can is the treatment recommended when attacks occur. Dieldrin usually remains effective for two (2) years after application.
Seedlings in pots are treated with Dieldrin before distribution and are therefore protected for the first two (2) years.
Young trees may be saved during rainy weather by early:
- Removal of the grubs
- Placing sand around the stem below ground level to encourage the development of new roots and
- Cutting back the trees and halving remaining leaves.
Rats and woodpeckers destroy ripening cocoa pods. Poisoning rats is easily and cheaply carried out with Rodenticide Blocks. Warfarin, the poison in the Blocks only kills when taken continuously for four to five days. It leads to internal bleeding which is stopped by vitamin K in the blood, causing the rats to recover when the daily dose is discontinued before five (5) days.
Rodenticide block is to be divided in quarter pound pieces and placed (or tied out of reach of children or dogs) on one in every thirty (30) trees. About three (3) days after setting blocks, checks should be made to see whether more poison is needed.
Woodpeckers’ damage is much less common than that of rats. The Woodpeckers make small, straight-sided hole without teeth marks around the edge and remove only a small amount of beans. In rainy weather the remainder of the beans will sprout unless collected soon after damage.
Climate and Soil Requirements
Cocoa requires a relatively heavy rainfall of over 60 inches per annum. Very heavy rainfall of over 120 inches per annum will encourage growth and bearing, but the incidence of Black Pod and Frosty Pod Rot diseases are usually very high and unless controlled, will reduce yields.
The two (2) chief soil requirements in Jamaica are depth and absence of free or absorbable calcium. The soil should be at least two (2) feet deep.
Free or absorbable calcium interferes with the absorption of iron, which is especially required for the production of chlorophyll, the green colouring mater of the leaves. When absorbable calcium is present, leaves show a yellowness or chlorosis, the plants yield poorly and are short-lived.
Cocoa should be planted at 10 feet x 10 feet. Before planting it is necessary to:
- Set up erosion controls
- Establish temporary shade
- Obtain good shade from temporary shade plants. Bananas and plantains may be planted 12 feet x 6 feet apart, or if set 8 feet by 8 feet, cocoa plants may be planted alternately next to and between temporary plants.
- Prepare planting sites well in advance when soils are heavy clays.
- Wait until sufficient rains are assured.
The usual erosion controls are:-
- The selection and protection of the required number of sun-offs drains, and
- Erosion control drains, with 1 in 100 falls, leading to run off drains. Drains are not required when soils are free draining.
Planting sites are best prepared well in advance to allow the soil to settle. Open a one and a half foot deep and one and a half foot wide hole. Fork in about three inches of well-rooted manure of leaf mound if available and fill with top-soil to encourage rapid downward growth of roots and thus reduce the effect of drought. Spread the bottom soil around or below the site. On a hillside make a “bench” planting site.
The actual time of planting should depend on the assurance of rains. Do not plant until consistent rains are expected to continue for at least a month afterwards.
The cultivation required is chiefly weeding. Unless plants are kept cleanly weeded they will not make uninterrupted good growth.
Young plants may be circle forked in advance of their roots, but this should cease when roots meet. It is best also to mulch young plants before a drought.