Originating in Africa, watermelons (Citrullus lanatus) were first cultivated in Egypt where testaments to their legacy were recorded in hieroglyphics painted on building walls. The fruit was held in such regard that it was placed in the tombs of many Egyptian kings. Watermelons were brought to China around the 10th century and then to the Western Hemisphere shortly after the discovery of the New World. Now, much of the commercial supply of watermelons is grown in Russia. In addition to Russia, the leading commercial growers of watermelon include China, Turkey, Iran and the United States.
Watermelon is a warm season crop, which requires dry weather with abundant sunshine for quality fruit production. The crop can be grown on well drained sandy, sandy loam or alluvial soils. A pH range of 6.0-7.0 and temperature range of 24-27° C are considered optimum for the growth of the vines. 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.
Arka Manik: Improved variety released from the Indian Institute of Horticultural Research (IIHR), Bangalore. Fruits are oval, light green rind with dark green stripes. Fruits are very sweet with pleasant aroma; and deep crimson coloured flesh with granular texture. Average fruit weight is 6 kg. Resistant to powdery mildew, downy mildew and anthracnose. Duration is 110-115 days. Yield is 60 t/ha.
Sugar Baby: Released from the Indian Agricultural Research Institute, New Delhi. The fruits are slightly small in size; round shaped having bluish black rind and deep pink flesh with small seeds. Average weight is 3-5 kg. The fruits ripen in 85 days.
Arka Jyoti: Released from the IIHR, Bangalore. Mid season variety; fruits are round; rind colour is light green with dark green stripes and crimson coloured flesh. Average fruit weight is 6-8 kg.
Durgapura Meetha: A late maturing variety released from the Agricultural Research Station (ARS), Durgapura, Rajasthan. Fruits are round, rind is thick and light green in colour. Flesh sweet and dark red in colour, good keeping quality, average fruit weight is 6-8 kg. The fruit ripens in 125 days.
Durgapura Kesar: A late maturing variety released from the ARS, Durgapura. Rind is green in colour with stripes; flesh yellow coloured, moderately sweet with large seeds. Average fruit weight is 4-5 kg.
Propagation & Planting
Approximately 1.0-1.5 kg of seeds are required for cultivating one hectare of land. To improve germination percentage, soak the seeds over night in water, drain and keep wrapped in wet gunny bags.
December-April is the ideal seasons for growing watermelon. Prepare the soil to a fine tilth by ploughing and harrowing. Various systems of sowing can been adopted.
a) Pit method: Pits of 60 cm diameter and 30-45 cm depth are taken at a distance of 3.0x2.0 m apart. Well rotten FYM and fertilizers are mixed with topsoil in the pit and four or five seeds are sown in a pit. Remove unhealthy plants after two weeks and retain two or three plants per pit.
b) Furrow method: Furrows are opened at a distance of 2-3 m apart. Sowing is done on either sides of furrows and the vines are allowed to trail on the ground. Dibble 3-4 seeds at a distance of 60-90 cm along the furrow.
c) Hill method: While planting in riverbeds, pits of size 30 x 30 x 30 cm are dug at a distance of 1-1.5 m. The pits are filled with equal quantities of soil and FYM. The soil is piled up in the form of a hill and two seeds are planted on each hill.
Gap filling and thinning
Under ideal conditions, the seeds germinate within 8-10 days after sowing. Two to three healthy seedlings are retained at each spot while the rest are removed or used for gap filling.
Apply FYM @ 20-25 t/ha as basal dose along with half dose of N (35 kg) and full dose of P2O5 (25 kg) and K2O (25 kg/ha). The remaining dose of N (35 kg) can be applied in two equal split doses at the time of vining and at the time of full blooming. A fertilizer dose of 70:25:25 kg N:P2O5:K2O / ha in several splits is recommended in Onattukara region. The fertilizer dose per pit would be 28:10:10 g N:P2O5:K2O.
Irrigate at three or four days interval during the initial stages of growth. Irrigation should be given on alternate days during flowering and fruiting. When fruits are mature, the frequency of irrigation may be reduced. Application of water should be restricted to the base of the plant or root zone to avoid wetting of the vines or vegetative parts, as it will promote diseases and rotting of fruits. Mulching will also help to reduce moisture loss.
For trailing the watermelon, spread dried twigs on the ground.
Spraying NAA @100 ppm at two leaf stage and repeating the same after 6-7 days is effective for increasing the percentage of female flowers.
To allow the side shoots to grow, remove apical shoots when the vines are 1m. This practice gives significantly higher fruit yield. At the initial stages of fruit setting, malformed, diseased and damaged fruits are removed and only 2-3 fruits per vine are retained. This results in increased fruit size and yield.
Conduct 2-3 weeding operations; the first being done at 20-25 days after sowing while subsequent weedings are done at an interval of one month. When the vines start spreading, weeding in between the rows, or ridges, becomes unnecessary since vine growth can smother the weeds.
Watermelons can be profitably intercropped in newly planted orchards during the initial years provided there are sufficient irrigation facilities.
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.
Control: Spraying carbaryl (4g/litre) during the seedling stage effectively controls the pest.
Aphids: Aphis sp.
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.
Control: The aphids can be easily controlled by spraying malathion (0.1 %) or rogor (0.1-0.2 %) sufficiently early before the attack becomes severe.
Fruit fly: Dacus cucurbitae and D. dorsalis
The fruit fly maggots causes 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 summer rains when the humidity is high.
Control: 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 carbaryl or malathion 0.15% suspension containing sugar/jaggery @ 10g per litre water at the time of flowering partially check the fly incidence.
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.
Control: Acaricides like dicofol (0.05 %) and wettable sulphur (0.3 %) gives effective control of mites. Cutting and burning of severely infested plant parts reduces further multiplication of mites.
Powdery mildew: Sphaerotheca fuliginea
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 shrivelled; and defoliation may occur. Fruits of the affected plants do not develop fully and remain small.
Control: Carbendazim (1ml/litre) or karathane (0.5 ml/litre) is sprayed immediately after the appearance of the disease. Repeat the spray 2-3 times at an interval of 15 days.
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.
Control: Repeated sprayings at 5-7 days interval with dithane M 45 (0.2 %) effectively controls the disease.
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.
Control: Three sprays of karathane (6g/10 litres) or bavistin (1g/litre) 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.
Control: Excellent control of this disease can be achieved with ridomil (1.5 g/litre of water), which must always be used simultaneously with a protectant fungicide such as mancozeb (0.2%) to prevent the development of resistant strains.
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. Maturity indices of watermelon are withering of tendril and change in belly colour. The mature fruits on thumping give dull sound as against metallic sound of unripe fruits, which is also a good indication. Fruits should be harvested from the vines with the help of a knife.
The yield of watermelon varies between 20-25 t/ha according to variety, season, etc. 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. 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 flavor to watermelons.