Continuation of the article published in R.F.C. of A. Newsletter, March 1985

Planting, continued from Part I
In the orchard, the plants may be set at a distance of 8-10 m or more following the square or triangular systems of planting. Some workers recommended a wider spacing of 12-14 meters. Planting may be done any time of the year provided the soil is not very dry and there is a good supply of water to irrigate the newly-planted seedlings. Otherwise. planting is best done at the onset of the rainy season to avoid the problem of watering. If a dry spell occurs soon after planting, hand watering is necessary until the plants are well established.

Intercropping
In many Philippine homes, the jak is usually grown in a mixed planting of fruit and other crops in the backyard. It is also a good intercrop in coconut groves. In India, it is used as an intercrop for mango and citrus and as a shade tree for coffee and black pepper. In an orchard crop, the spaces between the jak trees may be cultivated and planted to some annual crops to add to the income of the grower. This may be practiced at the prebearing age of jak or until the trees have not yet closed in. The growing of intercrops should be stopped as soon as they materially interfere with the cultural operations in the orchard.

Mulching and Cover Cropping
During the dry season, the area around the base of the trunk should be mulched to conserve the moisture in the soil. The mulch also serves as a source of organic matter and nutrients once it is decomposed. When it is no longer economically profitable to cultivate cash crops in the orchard, a leguminous cover crop is advisable to grow to help control weeds and to reduce moisture loss from the soil. The cover crop should be pressed down when its growth becomes too thick. It should not be allowed to climb the jak trees.

Irrigation
The plants should be watered right after transplanting in the field, especially if no rain is expected. To facilitate the establishment of the plants, irrigation should be practiced during the first to the second year particularly during the dry months. In later years, the water requirement is less critical. Mulching the trees may be sufficient to conserve the moisture in the soil to last until the next rainy season. With irrigation facilities available, it is a good practice to water the trees during the dry season.

Fertilization
In the Philippines and perhaps in other countries as well, jak trees are seldom fertilized. Despite this neglect, the trees still continue to bear fruits. This does not necessarily mean that they would not benefit from fertilizer application. As a general fertilizer recommendation, about 100-150 g ammonium sulfate should be applied per plant one month after planting, and an equal amount 6 months later or towards the end of the rainy season. If organic fertilizers are available, it is also advisable to apply these around the trees. As the trees grow bigger, the amount of commercial fertilizer should be correspondingly increased. When the trees start fruiting, 0.5-1.0 kg complete fertilizer may be applied per tree at the start of the rainy season and an equal amount towards the end of the rainy season. As the trees grow older and as fruit production increases, the amount of complete fertilizer to apply should be correspondingly increased. A full-grown tree (15-20 years or older) may require at least 2-3 kg of complete fertilizer per application.

Pruning and Training
The first pruning is done before or during planting when excess shoots of seedlings are removed and the remaining leaves are pruned in halves to minimize transpiration. After this, no additional pruning is usually done until the tree starts to bear fruits. At this stage, pruning consists essentially in removing small, unproductive branches in the interior of the tree. Jak fruits are usually produced on the trunk and large branches; thus, the removal of unwanted branches would give more room and light to the developing fruits. Bagging of fruits would also be done easier. Diseased and insect-damaged branches should also be pruned regularly.

In India where the jak tree is used as a shade for coffee, a special training technique is practiced. This consists in training the plant to develop a single stem that grows vertically up to about 5 - 8 m from the ground level. All lateral branches below this height are cut off and only the top branches are allowed to spread laterally to provide the necessary shade for the coffee plants.

Disease Control
In the Philippines, no serious diseases are apparently attacking jak. However, inflorescence rot, (Rhizopus nigricans), pink disease (C. salmonicolor) and rhizoctonia thread blight (Rhizoctonia koleroga) are common diseases. These diseases may be controlled by removing and burning the diseased parts and spraying the trees with cupravit or Bordeaux mixture at recommended dosages.

Insect Pest Control
Two major insect pests are always a threat to successful jak production in the Philippines. These are the cerambycid bark borer, Batocera rubus L., and the nangka fruitfly, Dacus unbrosus Fabr. The larvae of the former pest bore into the bark, impairing the growth and causing the plant to wither. Infestation by the borers may be reduced by removing and burning the affected branches where the eggs are laid.

The fruitfly causes considerable damage to the jak fruits. The eggs are laid in or under the fruit skin and are hatched after 5-6 days. The larvae feed on tissues and work their way inside the fruit. They produce holes and cause rotting. Generally, a fruit becomes 50 percent or more rotten if it does not fall before maturity, becomes unfit for commercial purpose, and only partly fit for home consumption. Nine days after hatching, the larvae come out of the fruit and fall off to the ground to pupate in the soil. The fruitflies emerge after 12 days. The adults mate 3 or 4 days after emergence and the female adults lay eggs 4 days or more after mating. Oviposition usually takes place late in the afternoon, the female adult laying about 100 eggs in a cluster in one oviposition. The flies are most abundant in December to February and least abundant in May to June.

To reduce fruitfly infestation, the attacked fruits should be collected and burned. If the fruits are covered while still young, they can reach maturity without being attacked by the insects. Wrapping materials commonly used are gunny sacks, used cement bags, coconut leaves, rice straws, dried banana bracts and similar materials. Newsprint, it has been found, can also be used and can give 100 percent protection. The newsprint is not destroyed by rain even as alternate wetting and drying make it tougher. However, rain and strong winds can destroy the material. When this happens, the newsprint covering should be replaced within a day or two, otherwise the fruit is prone to infestation. Spraying young fruits with sevin or malathion at recommended dosages may also reduce fruitfly damage.

Harvesting
Seedling trees start to bear fruits 6-8 or more years after planting. Grafts bear fruits in about 4-5 years. In India, it is a common practice to injure or inflict wounds on the bark of the trunk and branches at intervals with a bolo to induce profuse fruiting, especially on shy-bearing trees.

The flowering and fruiting season of the jak varies in different locations. In general, flowering takes place almost continuously throughout the year so that the fruits may be found in all stages of development on a tree. In the Philippines, the fruiting season is March to August. Yield varies greatly from 20-500 fruits among seedling trees. A mature tree that bears 100 fruits annually is considered a heavy bearer. Fruit weight varies considerably and may be as much as 50 kg, although the average is around 20 kg or less.

Determining the right time to harvest the jak fruit may be a problem to the inexperienced. Some of the indicators used locally to determine fruit maturity and harvest time are (a) the sound given off by the fruits when tapped with the fingers, (b) the change in the color of the skin, (c) the distance between the spines, and (d) emission of the characteristic aromatic odor. A mature fruit produces a dull, hollow sound when tapped. This index of maturity is also followed in India. The mature fruit also forms widely spaced spines which yield to moderate pressure. The skin changes its color from light green to greenish or brownish-yellow. One or more of these 3 indices may be used for fruits for the market. For home use, the emission of the characteristic aroma of the jak fruit may be used as index of its maturity.

In harvesting, the fruit stalk is cut from the branch with a sharp instrument, such as a pruning shear, knife or bolo. For very large fruits, a second person is necessary to hold the fruits so that they will not fall to the ground. To harvest fruits from tall trees or fruits located at the top of the tree, the fruits are placed in a sack tied around the stalk with a rope and slowly lowered to the ground.

Marketing and Grading
After harvesting, the jak fruits are brought to the markets in jeep or truck. They are sold whole or sliced into pieces. Sometimes, the pulp is extracted and sold by weight.

The Philippine Trade Standard promulgated in 1970 PTS No.051-09.00 for the grading and classification of mature jak fruits. The fruit is considered mature when it emits its characteristic aromatic odor and when its spines are set far apart and are well-developed. The fruits are classified according to size as follows: Large when they weigh 15 kg or more, medium when they weigh 8 kg to less than 15 kg, and small when they weigh less than 5-8 kg.