other cocoa diseases

Combating D and other cocoa diseases

By W. M. Middleton

of Karkar Island, New Guinea

One of the biggest problems facing cocoa producers to lay especially in the Rabaul-Kokopo Districts of New juinea—is the incidence of Dieback disease.

was first discovered in recent s on Kulili Estates, Karkar id, some 10 or 12 years ago and is taken a large amount of labour ontrol it. he fungus Diplodia is always ent and known throughout the d by its attacks on other com ity-producing trees. usually gets an entrance through branches where there is a wound ait and spreads until it reaches trunk, eventually killing the tree. 0 chemical treatment has yet 1 found for Dieback. The big :ulty is that the fungus works ugh the centre of the wood of :ocoa tree. Sprays are useless. allowed to get out of control it d ruin a plantation. From lory this happened in cocoa areas ted around Buna and Dobadura o 60 years ago.

The disease can be treated if it is noticed in time on the branch and the affected part is cut off to at least six inches from where the fungus finishes.

Care should be taken to burn all the diseased wood from treated or dead trees.

Specimen pod

Some trees appear to be more resistant to Dieback than others and it may be a good idea, when a diseased tree is cut out, for the labourer to bring in a specimen pod, if possible.

This may enable one eventually to get an idea of what type of tree may be more resistant to the disease.

If seed from these trees is selected to be used for new plantings, it may reduce the incidence of the

disease, but it will take some time to prove this.

Cocoa in New Guinea has, for the most part, been interplanted with coconuts—the latter providing the shade.

This shade is adequate when the coconuts are about 15 to 25 years old—when they attain a height of about 30 to 40 ft.

When they get higher— to 50 or 60 ft—the shade generally is not sufficient and too much sun gets through to the cocoa trees below.

Cocoa needs some sun, but not a lot.

Shade would not be sufficient in some of the old coconut areas of Rabaul and Kokopo, which were planted by the Germans before World War I.

On Kulili we have tried to find out when the cocoa trees are getting too much sun by seeing if the trees are shaded sufficiently at midday.

If they are not, we plant a quick growing fern, like Leucaena glauca, near the over-exposed trees. This seems to help control Dieback.

Too much sun and wind are the

n things that damage cocoa ige. It follows that a healthy is more resistant to disease, anker is another disease prevalent 4ew Guinea. It can be recognised n the cocoa tree trunk exudes a jry fluid. his disease is caused by the ;us Phytophera, which is pink. lodia is a greyish colour, ther pests, such as the Lognicorn le and several types of borers, sometimes do quite a lot of iage on plantations but they ;rally can be controlled, eaf beetles and white ants also e trouble at times but can be Led by constant supervision and ying. think it is very important to clean s from around the cocoa trees cultivate the earth around the of the trees where some pests their eggs. he basis of growing cocoa essfully. in my opinion, is keep the plantation in good order ;r leguminous creepers and the itant use of indigenous labour ombat pests and diseases in areas re they are present. young cocoa trees are ted it is advisable to keep the of the young trees clear of grass weeds. The trees then will grow )t quicker than if they had to pete with undergrowth, flien preparing cocoa beans the t important thing is the ferment of the beans. Poorly fermented >a will result in inferior products, n Kulili, cocoa beans are lented for eight or nine days the cocoa is turned in ferment boxes every 48 hours.

The beans should start to heat up during the first 48 hours and reach their zenith in about seven days.

Then the heat will gradually decline, but still retain reasonable heat.

Sun dryer

The normal method is to use a thermometer to register the but it can also be judged fairly accurately by putting one’s hand down to the centre of the box.

After the eighth or ninth day, the cocoa is put out on the sun dryer for about four days, depending on the weather.

It is raked over and turned con tinuously to ensure even drying.

When sun-dried, the beans are finished off in a rotary hot air dryer which gives them a good polish, which generally appeals to the buyers.

However, if no mechanical dryer is available, a complete sun-drying produces good beans if they are turned frequently and they can be polished to improve their appearance.

With sun-drying and mechanical hot air drying of beans, there is little chance of the beans shrivelling. If the beans are put straight into the dryer from the fermenting box some shrivelling could occur because of the quick drying.

Buyers say sun-drying helps to give the cocoa a good flavour and more gradual drying prevents the beans from shrivelling. However, all my remarks are based on my experience at Kulili and they may not necessarily apply to all other cocoa-growing areas of the territory, where planters have their own methods.