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WATER MELON (CITRULUS LANATUS)
Watermelon belongs to the family Cucurbitaceae. It is related to the cantaloupe, squash and pumpkin, and other plants that also grow on vines on the ground.
Watermelons can be round, oblong or spherical in shape and feature thick green rinds that are often spotted or striped.
Water melon plant
Ecological Requirements
Altitude
Water melons can grow at altitudes of up to 1500m. Elevations of up to 1000m are ideal. Best growing areas are the lowland areas with high temperatures and relatively low rainfall, where irrigation is necessary.
Rainfall
Best results are obtained in low to medium rainfall areas, with additional irrigation. Optimum rainfall requirement per cropping season is 600mm, but 400 mm is considered minimum. Excessive humidity may cause leaf diseases and also affect flowering.
Temperature
Watermelon is a warm season crop, which requires dry weather with abundant sunshine for quality fruit production. They grow best under hot temperatures. Water melons do well at optimum temperatures of 22-280C. Cool nights and warm days are ideal for accumulation of sugars in the fruits. The seed germinates best when temperatures are higher than 20° C. High humidity at the time of vegetative growth renders the crop susceptible to various fungal diseases. Stagnation of growth occurs at temperatures less than 150C.
Soils
The crop grows best on well-drained sandy, sandy loam or alluvial soils. Well drained heavy soils can also be utilized. The soils should be rich in organic matter. Soil pH range of 6 to 7.5 is preferable.
Varieties
| Varieties | Description | Remarks |
| CharlestonGray
|
The fruit is oblong shaped; rind is light green with light stripes and flesh is red. Matures in 90 days | Require relatively long hot seasons for good development. Grows well wide range of well drained soils. |
| Sugar baby | The fruit is round with dark green rind; flesh is deep red, crisp and sweet tasting. Matures in 80 days | Require relatively long hot seasons for good development. Grows well wide range of well drained soils. |
| Crimsonsweet | Produces melon with sweet red flesh, high sugar content, thin rinds and very disease resistant. Matures in 85 days | Resistant to anthracnose and fusarium wilt. |
| Congo | Has a firm, rough andOblong in shape. The skin is dark green with faint green stripes. Maturity period in 90 days | Shows resistance to anthracnose |
| Fairfax | Fruit has thin rind with light and dark green stripes. Flesh is bright red and has higher sugar content than the above varieties. | Shows resistance to anthracnoseThe yields are lower than above varieties |
Other varieties include:
Chilean Black, Tiffany Hybrid, Honeydew, Cresso F1
Land preparation
Soils should be well cultivated and ridges or mounds formed on which seeds are later planted. If soils do not have enough organic matter, apply up to 10 tons of manure.
Planting
Water melons are grown throughout the year in lowland areas but peaks of rainy season should be avoided. At higher elevations, cultivation should be done only during the warmer period of the year.
The seed rate is about 3 kg/ ha.
The seeds are sown directly on ridges or mounds. If sown on ridges, 2-3 are planted at a spacing of 1.5-2m x 80 cm and thinned to one after emerging. On mounds, 5-6 seeds are planted per mound at a spacing of 2 m x 2 m and later thinned to 2-3 plants. At 25-30 cm high (2-3 weeks after thinning), earthing up around the plant bases is recommended to prevent exposure to the sun.
Fertilizer and manure application
Spread 20 ton/ha or more of manure depending on the soil condition, and work it into the soil. Apply 10-12g (1 tea spoonful) of phosphate fertilizer with 46% P2O5 as TSP per hill before planting. 100-200kg/ha will be required.
Apply 1 teaspoonful (10g) CAN after thinning and a similar amount just before flowering. 200-250 kg CAN 26% is required for top dressing
Mulching
It keeps the moisture in the soil and protects fruits from dirt and excessive moisture. Straw is suitable as mulching material.
Pests
| Pests | Damage/ symptoms | Control |
| Red pumpkin beetle: (Aulacophora foveicollis) | Pumpkin beetles attack the watermelon at the seedling stage by making holes in cotyledonary leaves. As a result the seedlings in the young stage die. | Spraying with insecticides e.g. Pesthrin, Neemroc, Achook during the seedling stage effectively controls the pest. |
| Melon lady bird: (Epilachna spp) | Beetlees feed on leaves leaving a skeleton of veins | Use insecticide such as Karate, Decis, Bulldock star |
| Aphids: (Aphis spp) | Aphids damage the plants by sucking the leaf sap. In young stage, cotyledonary leaves crinkle and in severe cases the plants wither. The leaves of fully-grown vines turn yellow and plant loses its vigour. | The aphids can be easily controlled by spraying Desis, Karate, Bulldock early before the attack becomes severe. |
| Melon fly🙁Dacus cucurbitae and D. dorsalis )
|
The fruit fly maggots cause severe damage to young developing fruits. The adult fly lays eggs in the flowers. The eggs hatch into maggots, which feed inside the fruits and causes rotting. The fly attack is severe, especially after rains when the humidity is high. | There is no direct control of maggots because they are inside the developing fruits. The affected fruits should be regularly pinched off and buried in a pit. Spraying e.g. Pesthrin, Neemro, Achook at the time of flowering partially checks the fly incidence. |
| Two spotted spider mite (Tetranychus urticae) | Nymphs and adult mites suck cell sap. White patches appear on affected leaves, which become mottled, turn brown and fall. The pest attains serious proportions during summer. Different stages of mite are found in colonies covered by white-silky webs on lower surface of leaves. | Cutting and burning of severely infested plant parts reduces further multiplication of mites Use miticides e.g. Keltahne, Omite, Mitac |
Diseases
| Diseases | Symptoms | Control |
| Powdery mildew: (Erysiphe cichoracearum) | Symptoms start as white powdery residue on the upper leaf surface.On the lower surface of the leaves, circular patches or spots appear.
In severe cases, these spread, coalesce and cover both the surfaces of the leaves and spread also to the petioles, stem, etc. Severely attacked leaves become brown and shriveled; and defoliation may occur. Fruits of the affected plants do not develop fully and remain small. |
Chemical control e.g., Bayleton WP 25, Milraz Rindomil gold mz 60 WG, Nimrod 25 EC. |
| Anthracnose: Colletotrichum sp. | High humidity and moist weather favour the development of the disease. Symptoms appear on the leaf as black spots, which later turn pink in colour. In case of severe infection, the disease spread to the developing fruit. | Repeated sprayings at 5-7 days interval with Dithane M 45 (0.2 %) effectively controls the diseaseUse of chemicals like Cuprocaffaro 2727WP, |
| Fusarium wilt: Fusarium oxysporum f. sp. niveum | Initially the plants show temporary wilting symptoms, which become permanent and progressive, affecting more vines.The leaves of the affected plants show yellowing, loose turgidity and show drooping symptoms.
Eventually, the plant dies. In older plants, leaves wilt suddenly and vascular bundles in the collar region become yellow or brown. |
Three sprays of Karathane or Bavistin immediately on appearance of initial symptoms at 5-6 days interval controls the disease. Leaves of fully-grown vines should be thoroughly drenched during spraying. |
| Downey mildew: (Pseudoperonospora cubensis) | The disease is first seen as yellow angular spots on the upper surface of the leaves. Under conditions of high humidity, whitish powdery growth appears on the lower surface of the leaves.The disease spreads rapidly killing the plant quickly through rapid defoliation. | Excellent control of this disease can be achieved with Ridomil which should always be used simultaneously with protective fungicides such as Mancozeb (0.2%) e.g. Milthane super or Propineb e.g., Milraz to prevent the development of resistant strains. |
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| Melon fly | Red pumpkin beetle | Dacus cucurbitae |
| Powdery mildew | Downey mildew |
Harvesting
Harvest the crop in about 75-100 days after sowing depending upon cultivar and season. Fruits should be harvested at full maturity for local markets; while for transporting to distant markets, harvest slightly earlier.
Signs of maturity are: -
- Tendrils opposite the fruit die
- Dull sound when fruit is tapped with a finger compared to metallic sound of unripe fruits
- Vegetative parts start drying
- Changed fruit colour.
Fruits should be harvested from the vines with the help of a knife. The fruit is cut from the plant leaving a short stem attached to fruit and the cut part sprayed with a fungicide to prevent stem-end rot.
Yields
The average yields are about 20-30 tons per hectare depending on variety.
Grading
Harvested melons are graded according to their size, external appearances, symmetry and uniformity in appearance. The surface should be waxy and bright in appearance; devoid of scars, sunburn, transit abrasions or other surface defects.
Storage
Watermelons can be stored for 14 days at 15°C. While transporting in truck, stack the fruits on dried grass to avoid bruising and damages. For short-term storage or transit to distant markets, fruits can be stored at 7.2°C with 85-90 % relative humidity. Extended holding at this temperature will induce chilling injury. Do not store watermelons with apples and bananas as the ethylene produced from these fruits hastens softening and development of off flavour to watermelons.
Utilization
The fruits are popular for fresh consumption, although they are commonly grouped into vegetables. The fruit is served fresh as slices, as chunks (often in fruit salad), as juice, and as edible seeds for the confectionary types. Watermelon has extremely high water content, approximately 92%, giving its flesh a crumbly and subtly crunchy texture and making it a favorite thirst-quenching fruit. The fruit is an excellent source of vitamin C. It is also a very good source of vitamin A and B6. In addition, watermelon is a good source of thiamin, potassium and magnesium.