Pummelo Farming


Pummelo (Citrus maxima), Suha or Lukban or Pomelo is one of the most popular species of the Citrus family. It has a long shelf life that it can be transported to distant markets.

The pummelo/pomelo tree grows from 5-15 meters in height and has low spreading branches with a canopy size ranging from 500-900 centimeters. Its leaves are ovate to oblong with leaf size ranging from 5 cm x 12 cm to 8 cm x 20 cm wide when fully expanded.

The flowers are located either in the axial or terminal point, raceme type of inflorescence and fruit is yellowish green in color, nearly round to pear-shaped. It matures five to six months after flowering. The juice vesicles are either white, light pink or red, depending on the variety. Seeds are few to nil ridged, deltoid to globous in shape and mono embryonic.


Uses:

a. The fresh juicy pulp vesicles are eaten fresh out of the hand or in the fruit salad and sometimes the juice is extracted for beverage.

b. The white inner part of the peel can be candied after the outer peel containing oil glands have been removed.

c. In Vietnam, the aromatic flowers are used in making perfumes.
The wood is used for tool handles and firewood while leaves, flowers, fruits and seeds are sometime used as herbal medicine to treat cough, fevers and gastric disorders.

Properties:

The edible segments form only a small fraction of the thick-skinned fruit. A 100g edible portion is composed of the following:

Water (g) 89.00
Protein (g) 0.50
Fat (g) 0.40
Carbohydrates (g) 9.30
Vitamin A (IU) 49.00
Vitamin B1 (mg) 0.07
Vitamin B2 (mg) 0.02
Niacin (mg) 0.40
Vitamin C (mg) 44.00

Recommended Pummelo Cultivars

Magallanes

Origin Davao City
Yield (No of fruits /tree 227.00
Weight of fruit (g) 859.03
Edible portion (%) 44.20
Total soluble solids (%) 9.00
Flesh color Pink

Amoy

Origin Canton, China
Mantan Yield (No of fruits /tree 203.00
Weight of fruit (g) 814.83
Edible portion (%) 52.85
Total soluble solids (%) 9.22
Flesh color Pink

Siamese

Origin Thailand
Yield (No of fruits /tree 252.00
Weight of fruit (g) 1050.91
Edible portion (%) 51.07
Total soluble solids (%) 9.41
Flesh color White

Dela Cruz Pinl

Origin Lubongan, Toril, Davao City
Yield (No of fruits /tree 347.00
Weight of fruit (g) 784.76
Edible portion (%) 57.57
Total soluble solids (%) 9.67
Flesh color Pink

Soil and Climatic Requirements

1. Soil Requirement

a. Adapted to a wide range of soil types provided, they are reasonably deep, well-drained and aerated with high moisture retention.
b. Optimum pH range from 5.5-6.5.
c. Liming to increase pH when it is below 5 (acidic).
d. Water logged soils, sticky heavy soils, wet soils and those underlain with hardpan should not be used.

2. Climatic Requirement

a. Grows in lowland tropics in elevation up to 400 meters above sea level with optimum temperatures of 23-300C.
b. Optimum light requirement of 32.3-86.1 klux
c. Annual rainfall requirement of 1500-1800 millimeters.

Production of Seedlings for Rootstocks:

1. Select fully developed seeds from mature/ripe fruits of Calamandarin (bleieved to be a hybrid of calamondin and mandarin)

2. Seeds should be selected from fruit trees that are free from Citrus Canker (Xanthomanas Citri) to avoid contamination on the seed.

3. Fruit that dropped or fall on the ground should not be picked up and use as seedlings for rootstock.

4. Disinfect the seeds with CHLOROX at 5% solution, rinsed with tap water and air dry before sowing.

5. Seed beds (nursery) should be isolated from existing citrus orchard to prevent possible contamination through insect vectors.

6. Soil media should be light type (sandy loam) and free from any soil borne insect pests like root grubs and nematodes.

7. Sterilize the soil media.

8. Extracted seeds should be sown immediately to avoid drying.

Care of Seedlings for Rootstock

-Water the seedbed to facilitate germination.
-When seeds started to germinate, exposed the seedbed to sunlight. Do not put shades. Shades provide a microclimate which favors the growth of dumping-off pathogen. Seedlings that grow without shades are hardy and free from dumping-off disease.
-Seedlings do not need too much water. Too much water on poor drained beds predisposes the seedlings to dumping-off disease.
-Spray chemicals to protect young seedlings from pests and diseases.
-Recommended minimum dosage should be used to prevent leaf burn.

Potting and Transplanting of Seedlings

-Seedlings are ready for potting 21-28 days after germination in "7 x 12" x .003 polyethylene plastic bags containing garden soil and place them in the nursery.
-Avoid transplanting seedlings with deformed root system (goose-neck root)
-Calamandarin seeds are polyembryonic thus from 1 seed, 2-3 seedlings germinate. One of the seedlings that germinate is an off-type. This seedlings are characterized by their stunted growth, weak and the leaves produced are smaller that other seedlings. These seedlings should be eliminated.
-Water immediately the newly potted plants.
-Fertilize the seedlings when signs of new shoots or growth have developed.

Asexual Propagation and Care of Budded Seedlings

-Rootstocks are ready for budding in 6-8 months; or at least pencil-sized in stem diameter.
-Apply nitrogenous fertilizer at 5-10 grams per plant 2-3 weeks before budding.
-A round bud-stick give more good buds that angular bud-stick.
-Budding should be done at a height of 6-8 inches above the ground level.
-Do not fertilize newly budded plants; unless the bud eye have shown signs of growth.
-Remove the wrap of bud 3 weeks after budding.
-To hasten growth of bud-eyes, "lopping" or "cripping" the top of the seedlings 2-3 inches above the bud is recommended.
-When bud-eyes started to germinate; decapitate the rootstock 1-3 inches above the bud-eye union to force the growth of the bud-eye or scion.
-Weeding should not be done when the scion are succulent and tender, thus are susceptible to breakage when touch.
-Budded plants are ready for planting at 8 months old.

Orchard Establishment

Land Preparation

Clear/remove all stumps and grasses
Plow twice and harrow thrice to loosen the soil.
If the soil is acidic, incorporate dolomite lime during plowing and harrowing
Get soil sample for analysis.

Field Layout and Distance of Planting

The field layout should be either square or quincunx method depending on the topography of the orchard.

Distance of Planting

10 m x 10 m = 100 seedlings/hectare
8 m x 10 m = 125 seedlings/hectare
6 m x 8 m = 208 seedlings/hectare
8 m x 8 m = 156 seedlings/hectare
Preparation of Holes and Planting

-Dig a cubical hole measuring 50 cm. Wide and 50 cm deep. The hole will be filled up with a mixture of 50% decomposed measure, 50% top soil and 2 tablespoon of nematicide.
-Remove the plastic bag and plant the seedling into the prepared hole without breaking the ball of soil. Prune the roots to enhance root branching.
-Plant young plants at their dormant stage.
-Cover the hole with the soil-manure and press gently.
-Plant during the rainy season.

Care of the newly planted seedlings

1. Water the plants immediately after planting to assure close contact between soil and roots and prevent wilting.
2. Apply fertilizer when the newly planted trees started to developed new growth.
3. Weed control - weeds compete with the seedlings for nutrients, sunlight and water.
4. Mulching the trees with grasses, rice straw, rice hull and banana pseudostem will conserve soil moisture during dry period, prevent the growth of weeds and as source of organic matter after decomposition.
5. Wounds on the bark and branches should always be painted with water repellant paints.
6. Plowing and planting of intercrops should be 1-2 meters away from the rows or hills of the trees to avoid injury on the trunk, branches and roots
7. Prune the young pummelo tree and leave three main framework branches. The lowest branch should be 40-60 cm. off the ground.

Care and management of non-bearing and bearing trees:

Weeding. Weeds compete with the seedlings for nutrients, sunlight and water. Weeds must therefore be removed regularly or as the need arises. Avoid covercrops to creep around the base of the tree.

Mulching. Mulching prevents the growth of weeds, and help conserve soil moisture and serve as source of organic matter when decomposed.
During rainy season, however, mulch should not be placed to close to the tree because it is conducive to fungus.

Intercropping. Intercropping is done to maximize land use. Banana (lakatan, latundan) intercrop can serve as windbreak, shade and source of early income.

Irrigation. For sustained fruit production, it is important to water the pummelo before flowering and until after harvest to supplement rain.
Pummelo plants are moisture sensitive during flushes of new growth, flowering, fruit setting, and fruit enlargement. As a practical guide for irrigation, watering should be done when 20-30 cm of the top soil is dry.A matured pummelo requires 100-200 liters of water per day especially during flowering, fruit setting and enlargement to a month before harvest.

Pruning. Diseased and non-productive branches and water sprout using bolo, pruning shear or pruning saw must be pruned. All pruned surface must be painted to minimize entrance of micro-organisms and enhance healing. It is preferably done after harvesting.

Fertilizer Application and Management

1. Soil and Tissue Analysis

Soil and tissue should be collected and analyzed to determine the amount of fertilizer that will be applied. It is the most reliable way to determine the fertilizer requirements of pummelo.

Concentration of minerals found in branches, leaves and fruits of pummelo.

1. Elements Plant Parts

Fruits Leaves Branches
Nitrogen 2.0% 2.6% 1.2%
Phosphorous 0.2% 0.18% 0.17%
Potassium 2.0% 1.00% 0.75%
Calcium 0.8% 4.2% 1.8%
Magnesium 0.15% 0.25% 0.28%

2. Kinds of fertilizer

a.) Organic fertilizer

Fertilizer materials that came from living things. It can be animal manures or decomposed plant and animal bodies. This fertilizer material can:

Improve soil structure and non-toxic to the root
Improve soil aeration that encourage root elongation.

Contain less nutrients

b) Inorganic fertilizer

-materials from weathered rocks plus the nitrogen coming from the atmosphere.
granular from that contain on inert material called carrier.
-It contributes 80% I the soil mass
-Crop response in noticeable after a week
-Less bulky and easy to apply but expensive
-Makes the soil acidic, especially N fertilizers
-Toxic to the roots if applied in very high rates

3. Time of Fertilizer Application:

Apply fertilizer when there is a sign of shoot growth.

The recommended fertilizer levels should be applied in 2-3 installments; at the onset of rainy season, middle of rainy season, and towards the end of the rainy season

Fertilizer are applied by digging holes around the tree within the area covered by the canopy.

Fertilizers applied should be covered with soil to minimize surface evaporation and to prevent soil erosion.

Maximum efficient utilization of fertilizer was found in 20-30 cm deep and 100-150 cm from the trunk of matured pummelo trees.

Foliar fertilizer can be applied to supplement the soil applied fertilizers.
It was found that Potassium applied on foliage increases fruit size and sugar content of the fruit.

Foliar fertilizer are applied at 40 days after fruit set (DAFS); 60 DAFS; and 90 DAFS

4. Nutrient Deficiency Symptoms

1. Nitrogen (N)

retards enzymatic activities and vegetative growth
Yellowing of foliage
Twig die-back

2. Phosphorus (P)

Retard fruit development
leaf and fruit abscission
rough fruits
thicker rind

3. Potassium (K)

small fruit size
immature fruit splitting (rind disorder)
low sugar and acid content

4. Calcium (Ca)

Breaking of branch
short shelf life of fruits

5. Magnesium (Mg)

yellowing of foliage
reduce photosynthesis (low yield)

6. Zinc (Zinc)

Smaller leaves
chlorotic leaf spot
twig die-back
small size of fruits

7. Manganese and Iron (Mn and Fe)

Small size leaves
yellow color of leaves
low fruit setting
small size fruits

Harvesting

-Pummelo trees bear fruit 3-5 years from planting and can be harvested after 5-6 months flowering.
-Change in color - (green to yellow with 50% color change)
-Acid ratio is 10:1 with 9% Total Soluble Solids.
-Oil glands in the skin becomes more prominent and shiny.
-Juice content of 50% be weight
-Harvest pummelo fruits either by pulling or clipping from the fruiting branches
-The best time to harvest is around 8:00 am to 3:00 pm (with sunlight) to reduce fruit injuries on the peel of pummelo.
-Do not harvest pummelo fruits when the rind are still wet dry it before packaging.

Post harvest Handling and Management

Sorting. After harvest, the fruits must be brought to a shaded area. Sort the fruits according to size, color, and rind quality. Discard fruits that are injured, bruised, and misshapen.

Packaging. The fruits must be placed in kaing or wooden crates lined with newspaper or other suitable materials to prevent abrasions and punctures. Size of the containers depend upon the transportation system available

Storing. For longer shelf life, pummelo fruits can be stored for 12-14 weeks at a temperature of 120C and 85-90% relative humidity. Under ambient conditions, the fruits have a shelf life of 5-14 days.

Post-harvest treatment. For longer storage life, it is recommended to dip the fruits in thiabenzadole, benomyl or 2 amino butane at the rate of 500-1000 ppm. This will sustantially prevent the spread of post-harvest diseases and reduce losses.

Pests and Diseases and their Control

Insect Pests

1. Rind borer (Prays endolemma)

Plant Part Damage: Newly opened flowers and young fruits.
Control Measures: Apply pre and post bloom sprays with the use of either Cymbush, Gusathion, Decis at recommended dosage; Collect and burn or bury infested fruits.

2. Scale Insects

a. Snow scale ((Pinnaspis sp)

Plant Part damage: Trunks and twigs
Control Measures: Apply Dimethoate and oil-based materials

b. Black scale (Saissetia kemisphaerica)

Plant Part Damage: Trunks, twigs, and leaves
Control Measures: Spray malathion and recommended dosage.

3. Mites

Plant Parts Damage: Leaves and fruits
Control Measures: Spray Dicarzol, Kelthane, Malathion, Dimethoate

B. Bacterial and Fungal Disease

1. Citrus canker (Xanthomonas citri)

Symptoms: Lesion on both sides of the leaf and fruit ridges on the fruit
Transmission: Contaminated budwood, man, animals, tools, and wind
Management:: Burn severely infected trees or eradication; Spray any copper-based fungicide

2. Foot Rot (Phytophtora sp) Gummosis

Symptoms: Sap oozing from small cracks on the bark; lesions spread around the trunk

Management:: Use resistant rootstock; avoid deep planting; water management; aeration around the crown; surgical treatment; treat with copper-based fungicide

3. Pink Disease (Corticium salmonicolor)

Symptoms: White fan-shaped coating of mycelia growth becomes pink; Bark is destroyed, girdled and die

Management: Remove affected barks of trunks and prune diseased parts; disinfect by spraying copper fungicide or lime sulfur mixture

4. Fruit Rot (Diplodia natalens)

Management: Burn rotten fruits to prevent spread of the spores

5. Scab (Sphaceloma faucetti)

Symptoms: Disease starts as small, pale orange, circular spots on young fruits. As disease advances and fruits start to mature, several lesions coalesce and form irregularly shaped spots.

Management: Spray copper fungicides at the time when new flushes of growth appear or at time of blooming when two-thirds of petals have fallen. Successive sprays may follow two weeks thereafter up to the time when fruits are half matured.

C. Virus and Virus-like Diseases

1. Greening/Leafing mottling

Causal Organism: Fastidious bacteria
Carrier: Diplodia citri (Jumping plant lice)
Integrated Disease Management:
Eradicate infected plants
Use disease-free planting materials
Shoot tip grafting
Health indexing and spraying of insecticides (Dimethoate) on citrus trees at shooting stage
Biological control of psyllid vector (Octoparasites)

2. Triztesa (Virus)

Symptoms: Stem pitting
Most varieties of citrus are affected by stem pitting disease which develop large number of pits on trunks and stems

Carrier: Brown citrus aphids (Toxoptera citricidus)
Black citrus aphids (Toxoptera aurantii)
Melon aphid (Aphis gossipii)
Integrated Disease Management:
Use of resistant rootstocks
Mother trees where scions are obtained should be periodically examined and indexed

3. Exocortis (viroid)

Symptoms: Yellow stem blotches and dark splits; die-back; stunting; reduced yield
Carrier: Infected budwood, nursery tools
Integrated Disease management:
Selection and indexing test of non-infected budwood
Use of healthy budwood
Use shoot tip grafting to eliminate the pathogen
Disinfect tools used for budding and pruning with household chlorox.

4. Xyloporosis (viroid like)

Symptoms: Mild wood pitting to advance bark scaling; wood disorganization and impregnation of affected tissues with gums
Carrier: Infected budwood, nursery tools, and contaminated equipments
Integrated Disease management:
Selection and indexing test of non-infected budwood
Use of healthy budwood
Disinfect tools used for budding and pruning with household chlorox.

5. Psorosis (complex of viruses)

Symptoms: Chlorotic blotching in young and mature leaves; bark scaling of branches and trunks

Carrier: Infected budwood
Integrated Disease management:
Use of indexed budwood and seeds free of psorosis
Scions should be cut only from indexed trees known to be free from Taller leaf virus

6. Tatter leaf virus

Symptoms: Stunted growth

Carrier: Infected budwood and sap transmissible
Integrated Disease Management:
Infected materials can be made virus-free by combination of heat treatment and shoot tip grafting (STG)

Source: www.usm.edu.ph References:

CARRDEC Techno-Series, May 2005

Loquias, VL. And RT. Serapio. 1998. Technology advances in the commercial production of pummelo. A paper presented during the on-site techno-demo training on the cultural management of high value fruits. Naomi's Botanical Garden,

Banadero, Ozamis City. April 2-3, 1998. 24 pp.
Plant resources of South-East Asia. 1992. Edible fruits and nuts. E. W. M. Verheij and R. E. Coronel (Editors). Prosea Foundation. Bogor, Indonesia. 444 pp.

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