Dr. M. Irfan Ashraf1, Shoukat Sajad1, Rashid Iqbal1, CH. M. Sadique2
1Institute of Horticultural Sciences, University of Agriculture, Faisalabad.
2Deputy Director Fruit and Vegetable, Ayub Agriculture Research Institute
Introduction :- Bitter gourd(Momordica charantia L.) belongs to the family cucurbitaceae and is also known as bitter melon, bitter cucumber, balsam pear and African cucumber (Heiser,1979). The origin of Memordica charantia domestication likely lies in Asia, South China or possibly in Eastern India (Miniraj et al., 1993). The literature shows that it was cultivated early in India, as mentioned in Ayurvedic text written in Indian Sanskrit (Decker-Walters 1999). Both the putative wild and domesticated bitter gourd belongs to floras of India, Asia, Tropical Africa as well as New World tropics. It first came in Brazil through slave’s trade from Africa and spread into Central America (Marr et al., 2004). It is grown in Asia, Africa and Caribbean for edible purpose. It is herbaceous vine and can grow up to five meter long. The immature vine and fruit are used for many culinary purposes. The plant produces yellow color flowers, while male and female flowers are produced separately. The shape of the fruit is oblong, the center is filled with flesh and seed cavity is filled with pith and seeds. The bitterness in bitter gourd is due to cucurbitacins (Walters, 1999). The compound that creates the bitterness in bitter gourd is triterpene glycoside cucurbitacins like alkaloids momordicoside K and L (Jeffrey, 1980). Bitter gourd is a good source of carbohydrates, protein, zinc, phosphorous, calcium, iron, magnesium and vitamin C. It is used by diabetes patients for decreasing the blood glucose level. The ethno medical report shows that it is used in different folkloric medicines for various treatments of diabetes, ulcers, and infections (Beloin et al., 2005). Likewise, the juice extracted from fruits, leaves and whole plant is used for the treatment of infections, wounds, hepatitis, fevers and measles (Behera et al., 2008). The immature fruits and tender vine tips are used in a variety of culinary preparations. The fruits and shoots are soaked in salt water to remove some of their bitterness and then boiled, fried or pickled.
Plant description: This vine has a slender hairy stem with numerous branches and dense foliage. The plant grows up to 6 feet tall and develops small, yellow flowers both male and female, on the same plant. The fruits are green usually oblong, has an irregular surface with warts and 8-10 vertical ridges. When ripe, the fruits turn yellowish orange in colour.
Climate and soil: Bitter gourd is a warm season crop with wide adaptability. Ideal temperature for its growth and flowering is 25-30oC. Crop can be grown even in places of slightly lower temperature and high rainfall areas. Production of female flowers, fruit set and growth of plant are seen affected above 35oC and will be susceptible to viral infections. As seeds have a hard seed coat, germination is affected below 10oC. Well drained and fertile sandy loam or silt loam is ideal for the crop.
Preparing the field: Thorough land preparation and a well-prepared bed is required. Prepare a finely pulverized nursery bed of 1 m wide, 15-20 cm high and convenient length. Form 20 cm high beds during the dry season and 30 cm or higher during the wet season.
Planting: Direct seeding is the most common method of planting. In cooler climates, it may be necessary to start the seedlings in a greenhouse to ensure good germination.
Direct seedling: Optimum plant density differs with variety and usually ranges from 6500 to 11,000 plants per ha. In some intensively managed plantings, a closer spacing of 50 X 50 cm is used resulting in 40,000 plants per ha. On raised beds, sow two or three seeds per hole at a depth of 2 cm. Space holes 40-60 cm apart in rows spaced 1.2-1.5 m apart. Plants density using this spacing will range from 13,600 to 17,300 plants per hectare. When planted in warm soil, seedlings will emerge in a week or less. Thin to one seedling when they have four true leaves.
Transplanting: Sow seeds in small plastic pots or containers using a potting mix that has good water holding capacity and good drainage such as peat moss, commercial potting soil, or a potting mix prepared from soil, compost, rice hull and vermiculite or sand. Plant two or three seeds per container and thin to a single seedling when they have four to six true leaves. Water the seedlings thoroughly every morning to maintain a moist but not wet soil. Seedlings are ready for transplanting 15-20 days after sowing or when they are 10-15 cm tall. Bare-root plants will not survive so pull seedlings with their root balls intact before transplanting. Transplant seedlings into the field at spacing similar to those used for the direct seeding method.
Pollination: Bitter gourd needs insects to carry out the pollination process for setting fruits. If the insects are not available in the area, the pollination process can be done manually, by picking up male flowers and transferring pollens (face to face touching the central part of flowers)to female flowers. Female flowers have a fat section between the flower and vine system. This process should be carried out when flowering is active during the day time. If the pollination is successful, the fat portion will grow into full size fruit.
Staking and trellising: Bitter gourd grows very fast and vines elongate rapidly within two weeks after planting. Thereafter, The plant sends out lateral stems. Staking and trellising will increase fruit yield and size, reduce fruit rot and make spraying and harvesting easier. There are several methods of trellising bitter gourd, Bamboo poles, wood stakes, PVC pipes or other sturdy materials are used to provide support and keep the fruit and foliage off the ground. The trellis is arranged either in a lean to or tunnel structure. The trellis should be 1.8-2.0 m high, constructed from stakes 1.2-1.8 m apart which is almost similar to the plant row spacing. For the lean to type, the stakes are joined between two adjoining beds forming an A-shape structure. Horizontal stakes are installed at the top joining all other beds. The stakes support the climbing vines and lateral stems. Strings are used to secure adjoining stakes. Plantings are easier to manage and more productive when 2 m high rather than 1 m high string trellises are used. For the tunnel type, plants are grown inside an arch-shape structure made of either PVC or galvanized iron pipe. Plants are supported by bamboo stakes where vines freely climb and reach the top. The vines and lateral stems will then grow along the structure. Another type of trellising consists of a system of vertical strings running between top and bottom of horizontal wires or horizontal wires running across all directions on top.
Pruning: Bitter gourd develops many side branches that are not productive. To improve yield, remove lateral branches until the runner reaches the top of the trellis. Leave 4-6 laterals and cut the top of the main runner to induce early cropping. Removal of lateral branches in the first 10 nodes has a positive effect on total yield. Without pruning, most of the female flowers occur between the 10th and 40th nodes or at a height of 0.5-2.0 m.
Fertilizing: Bitter gourd requires a balance of nutrients from organic and chemical fertilizers. Fertilizer application rates depend on soil type, fertility level and soil organic matter. In sandy soils, fertilizer application consists of a basal application followed by four side dressings, providing a total of 184 kg N, 112 kg P2O5 and 124 kg K2O per ha. In clay or heavy texture soils, the entire amount of P and one third of N and K is applied before planting wither by broadcasting and tilling or by banding a few cm deep and to the side of the plant row in the bed. The balance of N and K is applied in two or more side dressings. No matter the soil type, the first side dressing is applied when plants have four to six true leaves. Subsequent side dressings are applied at two week intervals. Compost or manure can be used to satisfy the basal application of organic fertilizer.
Interculture: Being a shallow rooted crop, deep intercultural operations should be avoided. Land, particularly pits, should be kept weed-free by frequent hand weeding, hoeing and light earthing up along with application of fertilizers. Excess lateral branches, if any, may be pinched off for allowing plants to reach bower height at the earliest. Erect bower when plant starts vining. Plants may be trailed to bower by erecting small twigs in pits. Erection of bower is a costly operation and nearly 20% of cost of production is for making bower alone. Height of bower is adjusted as 2 m and is usually made of bamboo poles, G1 wire and thin coir or plastic wire. Bower once erected can be utilized for raising at least three crops.
Plant growth regulators: Application of several plant growth regulators like MH (50-150 ppm), CCC (50-100 ppm), Ethrel (150 ppm), silver nitrate (3-4 ppm), boron (3-4 mg/ha) at 2-leaf stage and 4 leaf stage increases the female flowers and yield in bitter gourd. Soaking of seeds with Ethrel or boron (3-4 mg/kg) also increases yield in bitter gourd.
Irrigation: Bitter gourd will not tolerate drought. Maintain good soil moisture in the upper 50 cm of soil where the majority of roots are located. Fields are furrow-irrigated every 10 days during the cool dry season and weekly during the hot dry season. During the rainy season, drainage is essential for plant survival and growth. In water limited environment, tickle or drop irrigation is an efficient method of supplying water and nutrients to bitter gourd crop.
Harvesting and Handling: Bitter gourd requires close attention at harvest time. The fruits develop rapidly and must be harvested frequently to keep them from becoming too large or too bitter. Normally it takes 15-20 days after fruit set or 90 days from planting for fruit to reach marketable age, however, bitter gourd can be harvested at earlier stages depending on the purpose for which it will be used. Fruit should be light green, thick and juicy and the seeds should be soft and white. Harvest every 2-3 days using a pair of scissors or a sharp knife to cut the fruit stalk. If a fruit remains too long on the vine, it will turn spongy, sour yellow or orange and split open. Bitter gourd yield can vary depending on variety and crop management. Average marketable yields are 8-10 t/ha. Fruits of bitter gourd don not keep long and should be sold in the market immediate. Remove damaged and deformed fruits. Carefully arrange fruits in bamboo baskets or boxes and store in a cool place at 12-13oC with 85-90% relative humidity. Under this condition, fruit storage life can be extended 2-3 weeks. Bitter gourd is chilling sensitive and damage may occur if kept below 10oC. Do not store fruits at temperatures above 13oC, as this will result in fruits turning yellow and splitting open. Keep harvested fruits away from other fruits (such as banana, pineapple and apple) that release large amounts of ethylene, a ripening hormone.
Yield: 20-25 t/ha.
Seed Production: For seed purpose, fruits are harvested when fruits turn yellow in colour. Seeds along with red placenta are rubbed against a hard surface and washed in running water and dried under shade. Seed yield: 200-250 kg/ha.
Common Varieties: Local varieties are Local Selection, Faisalabad Long, Chawenda etc.
Some imported and hybrid varieties are Prachi, Palli, BG 034, BG 034A, Gul-F1 etc.
Diseases: A large number of diseases affect the bitter gourd at different stages of growth. The major diseases of bitter gourd are as follows:
Powdery Mildew: Causal Organism: Sphaerotheca fuliginea
Symptoms: White, fluffy somewhat circular patches or spots which appear on the under surface of the leaves. Severely attacked leaves become brown and defoliation may occur. Fruits of affected plants do not develop fully and remain small.
Control: Fortnight spray of Carbendazim (0.1%), Culixin (0.05%), Karathane (0.5%) and Sulfex(0.2%) have been found effective. Seed treatment and seed drenching with systemic fungicides also give protection to young seedlings.
Downy Mildew: Causal Organism: Pseudomonas cubensis
Symptoms: It is a disease affecting most of the bitter gourd like cucumber, muskmelon, ridge gourd etc. It is prevalent in areas of high humidity, especially when summer rains occur regularly. The disease is characterized by formation of yellow, more or less angular spots on the upper surface of leaves. The disease spreads rapidly killing the plants quickly through rapid defoliation.
Control: Disease can be effectively controlled with sprays of Dithane M-45 (0.2%), Topsin-M and Elliote. One spraying gives protection for nine days. Copper oxychloride spray has also given good control. The sprays of Dithane M – 45 if given early and repeated 2-3 times can control the disease effectively.
Anthracnose : Causal Organism: Colletotrichum sp.
Symptoms: This disease is very serious in watermelon, cucumber etc. The spots on the leaves of watermelon first appear as small, yellowish, water soaked areas, which enlarge in size, that later coalesce and turn brown to black in color. Distinct elongated necrotic lesions having pointed ends appear on petioles and stems, and they later show cracks along with partial girdling of branches. When fruit pedicels are infected, young fruits shrived, darken and finally dry up. Lesions on fruits are circular, water soaked, sunken, dark-brown to black, and variable in size depending upon the age of the plant and weather conditions.
Control: The disease is effectively controlled by sprays of systemic fungicides, such as Benomyl, Bavistin and Thiophanate M (0.1%). Also it can be controlled by repeated spraying at 5-7 days interval with Dithane M-45 (0.2%).
Fusarium Wilt: Causal Organism: Fusarium oxysporum
Symptoms: It is a common disease affecting several crops like watermelon, muskmelon etc. There are also reports that Fusarium solani is causing wilt in muskmelon. In young seedlings, cotyledons droop and wither. In older plants, leaves wilt suddenly and vascular bundles in the collar region become yellow or brown.
Control: The disease can be checked to some extent by drenching the soil with Confidor or Hexocap or Thiride 0.2-0.3 % solution. Use of disease free seed and cultivation of resistant varieties is the best way to control the disease incidence. It is brought down by seed treatment with Carbendazin or Benomyl. Hot water treatment @ 55°C for 15 minutes also helps in eliminating seed-borne infection.
Alternaria Blight and Fruit Rot: Causal Organism: Fungal Disease
Symptom: Leaf blight has been recorded on muskmelon, watermelon and cucumber. Initial infection, small spots are noticed on the leaves, which rapidly increase in number and size. After coalescing of adjoining spots and on severely affected leaves, a burning effect or blight symptom is seen; especially in watermelon, concentric rings, typical of the pathogen arein variably present.
Control: Use of disease free seeds, its pre-treatment, crop rotation and proper drainage are effective means of controlling the disease. Borax wash (2.5%) at 45°C for 30 sec. or at 40°C for 2 min before packing of the fruits prevents fruit rot. Mancozeb and Ziram are effective at low temperatures.
Rhizoctonia Root Rot: Causal Organism: Fungal Disease
Symptom: The fungus is pathogenic to the bitter gourd, causing both pre- and post-emergence mortality. Older plants found to be less susceptible.
Control: Good control of the disease is obtained by seed treatment with Vitavax and Brassicol. Soil application of Brassicol and rotation with non-host crops are also recommended.
Virus Diseases: There are large numbers of viruses which cause much damage to bitter gourd. The leaves showing mosaic, crinkling, twisting and shortened internodes and flowering is adversely affected. Exact transmission has not been studied. There are some which are partially seed transmitted, some are transmitted through insect vectors like aphids and some are even mechanically transmitted. Chemical control of insect vectors by spraying Malathion at 5-7 days interval may partially check the spread. The complete control of virus disease has not been possible. One way of checking the spread is to dissuade the farmers not to collect seeds from virus infected plants, wherever the virus is transmitted through seeds. Some viruses are thermo-sensitive and get inactivated due to high temperature occurring in summer and sometimes virus affected plants do recover partially or temporarily. In the bitter gourd grown in rainy season, insect vectors like white fly spread the viruses rapidly. The only solution to control virus is the development of virus resistant cultivars. As far as possible the fields should be kept free of weeds, uncontaminated water should be used for irrigation as cucumber green mottle virus can be transmitted through water. For crops that are affected by CGMV, hygiene is important as the virus spreads easily by contact and contaminated tools. Avoidance of overlapped cropping will help to reduce the incidence of viruses transmitted by aphids or white flies. Use of mulches also reduces virus diseases incidence and helps in improving the yields. These should be tried in areas where virus disease is a problem.
The major pests of bitter gourd are as follows:
Red pumpkin beetle: The beetles attack most of the bitter gourd at seedling stage, especially at cotyledonary leaf stage. They make holes in cotyledonary leaves. Severe damage is caused at this stage, although they attack the vines in the grown up stage also. Muskmelon, pumpkin, cucumber and watermelon are attacked mostly with the exception of bitter gourd. Effective control can be done by spraying Carbaryl (sevin) 0.1-0.2 % or Rogor 0.1%.
Aphids: These small green insects (Aphis sp.) damage the plants by sucking the leaf sap. In young stage, cotyledonary leaves crinkle and in severe cases, the plants wither. In grown up vines, the leaves turn yellow and plant loses its vigor and yield. The aphids can be easily controlled by spraying Match, Imidacloprid, kararatay etc.
Fruit fly: This is the serious pest of bitter gourd. Maggots of the fly cause severe damage to young developing fruits. The fly attack is severe on muskmelon, bitter gourd, pointed gourd, watermelon etc. The fly attack is severe when the humidity is high. There is no direct control of maggots because they are inside the developing fruits. The adult flies can be controlled by using light-traps in the night and poison baits. Spray of Thiodan @ 6 ml per 4.5 liters of water also partially checks the fly incidence. Some newer chemicals like Methyl Eugenol is also effective. The affected fruits should be regularly pinched off and buried in a pit.
Mites: This pest is serious in muskmelon and watermelon, especially during severe summer weather. These tiny insects are seen on the undersurface of the leaves. Tiny spider-like creatures covered with fine self made webs colonize the ventral side of the leaves. Both nymphs and adults suck the sap, which results in yellowish specks on the upper surface of the leaves. The leaves gradually turns pale and then dry up. Spray of Diazinon 0.03 % or Lebaycid 0.05 % is effective.