Introduction
Ash gourd (Benincasa hispida) belongs to a monotypic genus Benincasa of the Cucurbitaceae family with the single cultivated species hispida synonym cerifera. The local names are wax gourd, white gourd, white pumpkin, hairy melon, Chinese preserving melon, winter melon, and petha kaddu (Indian). Ash gourd is normally grown in South-East Asia, and India up to an altitude of 1,500 m. In India, it is grown in Punjab, Uttar Pradesh, Bihar, West Bengal, northeastern hill states, Odisha, Kerala, Andhra Pradesh, Karnataka, Maharastra, and Tamil Nadu on a commercial scale. Mature fruits of ash gourd are used in making confectionery, i.e. candy, preserves, sweets, and pickles, and immature fruit (young) as a culinary vegetable in West Bengal, Odisha, Kerala, Tamil Nadu, and NEH Region of India. Fruit juice is used for treating a range of ailments, including epilepsy. It is also considered good for people suffering from nervousness and debility. The Chinese used this for a range of medicinal purposes. In Ayurveda literature, it is mentioned that the fruits contain tonic, nutritive and medicinal properties. The fruits are fleshy, succulent, and densely hairy at the immature stage but thickly deposited with a white easily removable waxy layer, of triterpenol acetate at maturity.
Table of content (toc)
Climate and Soil
Ash gourd requires a relatively stable high temperature, long days, and moderate humid climate for good growth. The most optimum temperature range for its growth is from 24-30°C. The development of more pistillate flowers is stimulated by low night temperature, short days, and humid climate, while male flower production is encouraged by high temperature, long days, and dry climate. High temperature and long day length are the important environmental factors that delay flowering in ash gourd but relative humidity and rainfall have little influence. Plants are sensitive to cold but can tolerate drought.
The crop can be grown on a variety of soils, ranging from sandy loam to clay loam rich in organic matter with good drainage. The soils with lighter textures that warm quickly are good for raising early crops of ash gourd. It can be grown in soils with a pH range from 5.0-7.5 but the most optimum pH range is 6-7. This can be grown in the soils that maintain the temperature in the range of 15.5-33.5°C with an optimum of 21.1°C. The soil moisture should be at least 10 to 15% above the permanent wilting point for its successful cultivation.
Varieties
CO 1: This variety was developed at TNAU, Coimbatore, through selection from a local collection. Fruits globular (35 cm long and 22 cm in girth), large with an average weight of about 6.8 kg. First harvesting is done about 100 days after sowing with an average yield of 20-25 tonnes/ha.
CO 2: This variety was developed at TNAU, Coimbatore. Fruits are spherical, small-long, and with an average weight of 3 kg. It has a yield potential of 23-25 tonnes/ha in 120 days of crop duration.
Indu: This variety was developed at the College of Horticulture, Vellanikkara, through selection from an indigenous collection. Fruits are round, 24.3 cm long, and 23.78 cm in breadth with an average weight of 4.8 kg. It gives an average yield of 24.5 tonnes/ha.
Kashi Dhawal: This variety has been developed through selection from a local germplasm collection. Fruits oblong, each weighing 11-12 kg. The flesh is white with 8.5-8.7 cm thickness and the seed arrangement is linear. Crop duration is 120 days and yields a potential of 58 to 60 tonnes/ha. This variety is suitable for the preparation of petha sweets due to high flesh recovery. It is recommended for cultivation in the states of eastern India.
Kashi Surbhi: This variety has been developed at IIVR, Varanasi, through selection. Fruits oblong fruit, medium in size (9.5-10 kg), flesh white with 8.5-8.7 cm thickness, 2.5-3.0 fruits/plant, high flesh recovery, yield potential of 70-75 tonnes/ha. suitable for the preparation of petha sweets. It is recommended for cultivation in Uttar Pradesh, Bihar, and Jharkhand.
Kashi Ujawal: This variety has been developed at IIVR, Varanasi through selection. Fruits are globular, each weighing 10-12 kg and less-seeded; yield potential of 40-50 tonnes/ha in 130-140 days of crop duration. This variety is suitable for the preparation of petha sweets. It is recommended for cultivation in the states of Punjab, Uttar Pradesh, Bihar, Jharkhand, Karnataka, Tamil Nadu, and Kerala.
KAU Local: This variety was developed at KAU, Vellanikkara, through selection. Fruits oval to oblong with green color at tender immature stage and white at full maturity. The fruits are 45-55 cm long and the length: breadth ratio is 2.05 with an average weight of 6-8 kg. Flesh thickness is 5.1-6.2 cm. It gives an average yield of 28 tonnes/ha in crop duration of 105-120 days for mature fruit production, however, harvesting at the tender stage is advisable for better yield and culinary purposes.
Mudliar: This variety was also developed at TNAU, Coimbatore. Fruits are big and pale green in color. Recommended for cultivation in Tamil Nadu.
PAG 3: This variety was developed at PAU, Ludhiana, and released at the state level. Fruits globular, medium size with an average weight of 8-10 kg. Fruit color green at an immature stage and covered with a white shiny coat at maturity. It yields 70-75 tonnes/ha in a crop duration of about 145 days.
Pusa Ujjwal: This variety has been developed at IARI, New Delhi. Fruits oblong, ellipsoid, rind greenish-white, flesh white with an average fruit weight of 7 kg. Yield potential of 48-50 tonnes/ha (Kharif season) and 41-42 tonnes/ha (summer season). Its fruits are ideal for long-distance transportation. It is recommended for cultivation in Karnataka, Tamil Nadu, and Kerala.
Other varieties, i.e. KAG 1 (developed by CSUAT, Kanpur), PAG 72 (developed by GBPUAT, Pantnagar), and hybrids DAGH 14 and DAGH 16 (developed by IARI, New Delhi) have been recommended by the All India Coordinated Research Project on Vegetable Crops for release.
Cultivation
Planting
The recommended plant spacing for ash gourd is 3 m x 60 to 90 cm. The plant population varies between 5,000-6,000 plants/ha. The seeds are generally sown either on a raised beds or in pits. In the ridge and furrow method, the ridges are prepared manually or mechanically keeping a 3 m distance between two rows with a channel width of 40-50 cm. The seeds are sown on the edges of raised beds after mixing the recommended dose of fertilizers and insecticide thoroughly. Generally, three to four seeds are sown in each pit. The seed should be sown 2 cm deep in a vertical orientation. Seed takes 7 to 8 days for normal germination at a temperature range of 25-30°C.
Sowing time
In northern plains of India, the best time of sowing for rainy season crop is June-July in northern and north-western India and June to August in south India, while suitable time for summer crop is the second fortnight of February although, in southern India, the crop can be grown around the year. Suitable sowing time in hills of northern India is April-May. In northern plains, if an irrigation facility is available sowing may be done in April and crop should be raised at bower but the height of bower should not be more than 1.2 m, otherwise, the fruit may detach from the vine due to load.
Seed rate and seed treatment
The seed rate depends upon the variety, growing season, soil type, agro-climatic condition of the growing region, seed size, and sowing distance between rows and plants. The 1,000 seed weight of ash gourd varies between 62-75 g. If four seeds per pit with 60% germination are sown, the seed rate would be about 2.5-3.0 kg/ha at recommended plant spacing, keeping population density of 5,000 6,000 plants/ha and leaving 10% land area used in irrigation channel and path. Raising seedlings in polybags and then planting in pits prepared in the main field gives good yield. Two healthy seedlings can be planted in each pit. By transplanting, the seed rate can be reduced to 1.5 kg/ha. Seed treatment is done with carbendazim 2.5 g/kg of seed.
Training and pruning
Training and pruning at proper stage(s) are required for maintaining a balance between vegetative and reproductive growth. In ash gourd, prune all secondary shoots and leaves up to 0.9 m of the vine from the base. Vines are generally not trained in ash gourd. However, staking of plants particularly in April sown crop is helpful in checking the rotting of fruits as it will be ready in the rainy season.
Weeding
At the initial stages of crop growth, the weeds compete with crops for nutrients, moisture, light, and space causing huge yield reduction. First-hand weeding may be done about 15-20 days after sowing followed by shallow hoeing. A total of 2-3 weedings are needed in cropping duration. Herbicides can also be used for weed control in ash gourd. Pre-emergence application of pendimethalin or alachlor (1 kg/ha) may solve the problem of weeds up to 30-35 days after sowing. If weeds appear later in the season, they may be controlled by hand weeding.
Mulching
Organic mulches, which protect the root of the plant from heat, conserve soil moisture, reduce weed infestation and modify the soil and air microclimate, are successfully used in ash gourd. Mulch also improves the quality of fruits by avoiding their direct contact with soil.
Irrigation
Ash gourd has an extensive root system and responds well to irrigation. In a rainy season crop, no irrigation is required unless there is a long break in the rain, however, in a summer season crop, light irrigation is given just after seed sowing/planting to facilitate germination and establishment of the plant, and subsequent irrigations are given at 8-10 days interval. There should be sufficient soil moisture during flowering and fruit development. Over irrigation causes excessive vegetative growth, while waterlogging causes severe damage to crops. Irrigation is given in channels in ridge sown crops and flood irrigation is given during summer to create the microclimate, which will favor the growth, flowering, and fruiting. In ash gourd, initial vegetative growth, flowering and fruit enlarging are the critical stages for irrigation. Any moisture stress at these stages will reduce the crop yield and fruit quality.
Nutrition
A basal dose of farmyard manure (20 tonnes/ha) is recommended. In general, 50-100 kg nitrogen, 50 kg phosphorus, and 50-60 kg potash are recommended in different states.
The total amount of phosphorus and potash and amount of nitrogen is mixed and applied as basal dressing near the expected root zone at the time of furrow or pit preparations while the remaining % amount of nitrogen is given as top dressing in two equal splits about 20 days (start of vine growth) and 40 days (flower initiation) after seed sowing followed by hoeing and earthing up.
Diseases and pests
Diseases
Anthracnose: This disease is caused by Colletotrichum orbiculare or C. lagenarium. Symptoms are found on all above-ground plants parts. Light brown circular spots appear on the leaf, which later turns to deep brown. Elongated lesions observed on stem and circular to oval sunken lesions appear on the fruit and subsequently, fruits shrivel, darken and finally dry up.
Fruit rots: The decaying of fruits is a major problem during storage and is caused by Fusarium solani, Fusarium moniliforme, Verticillium dahliae, Sclerotium rolfsii, and Phomopsis cucurbitacearum. Rotting starts from the lower fruit portion that had been in contact with soil. White fungal growth, which later on turned into brown circular scelerotia, is observed on the fruit surface. This is more common in fields having high moisture during September-October. The infected fruits contain completely rotten seeds, which turn white, become hollow, and fail to germinate.
Fusarium wilt: This disease is more common in sandy soil and is caused by Fusarium oxysporum f. sp. benincasae. The symptom is characterized by yellowing of lower leaves, which gradually progresses on upper leaves. The plant soon after infection starts drooping followed by wilting, and later on wilting becomes permanent. The characteristic symptom was observed after splitting of roots and lower portion of stem as vascular browning. The severity of the disease is more if the soil is infected with the root-knot nematode.
Downy mildew: This disease is caused by Pseudoperonospora cubensis. Generally, at initial stage small, irregular, yellowish lesions appear on leaves. Old lesions become necrotic and are clearly demarcated with light yellow areas. In high humid weather, faint, white downy fungus growth is observed on the lower surface of the leaves.
Powdery mildew: This disease is caused by Erysiphe cichoracearum. White long patches or coating appear first on the undersurface of the leaves, which later spread to both surfaces, stem, petiole, and other succulent plant parts.
Watermelon virus (WMV): Most of the cucurbits: and cowpea plants act as hosts for this virus. The leaves of diseased plants develop mosaic or mottling accompanied by green vein banding and reduction in leaf size. The petiole and internodes are also shortened. The mosaic in ash gourd was reported from Gorakhpur and the virus was identified as WMV.
Insect-pests
Red pumpkin beetle (Aulacophora foveicollis syn. Raphidopalpa foveicollis): The red pumpkin beetle is very destructive, particularly in summer when the plants have two to four leaves. Adults feed on the cotyledonary leaves, damaging the seedling and foliage by biting and making the holes.
Leaf miner (Liriomyza trifolii):Leaf miner attack is observed more in the early crops. Leaf miner makes mines in the leaves, especially in mature leaves. The larvae scrap the chlorophyll and leaf tissues.
Fruit fly (Bactrocera cucurbitae): Fruit fly is infecting ash gourd throughout India. The adult female lays eggs in/on the fruit surface using a conical ovipositor. After hatching, the maggots feed inside the fruits, causing rotting and premature dropping of fruits and also making them unsuitable for consumption. Mature fruits of ash gourd are damaged more than immature ones. The flies are most active after summer rain (June) and the rainy season (July-August) in northern India.
Root knot nematode: The root-knot nematode (Meloidogyne incognita) is very common in sandy soil. The symptoms are characterized as a stunted and unthrifty condition of the plant. Infected plants become pale to yellow. The plant canopy and fruiting capacity of the infected plants are reduced drastically. The characteristic symptoms are clearly observed after uprooting the plants as swelling and gall formation on roots and rootlets. Small, round, oblong to irregular galls are formed as a result of hypertrophy and hyperplasia of the cell.
Harvesting and post-harvest management
Harvesting
The crop matures in about 90-140 days after seed sowing. The yield depends on several factors such as variety, growing season, soil type, and climatic conditions of the growing region. In general, the average yield of open-pollinated varieties of ash gourd varies from 30-70 tonnes/ha, and of hybrid from 35-70 tonnes/ha. Small, solid, green, hairy, immature fruits, which are usually harvested after 10-12 days of anthesis, are best for culinary purposes. The immature fruit should have uniform color and size with partially developed seeds. The development of a thick layer of white wax is the index for judging the right stage for the harvesting of fruits at full maturity. Using a sharp knife, harvesting is done leaving a long peduncle attached with fruit. Fruits harvested at the fully mature stage have a good keeping quality than the fruits harvested at the immature stage and can be marketed to long distances since mature fruits are largely purchased by the confectioners who prepare candy, preserves, and bari.
Storage
Green immature fruits can be stored for 10 14 days at 10-12.5°C temperature and 85-90% relative humidity. However, the mature fruits having a thick layer of wax may be stored for up to 3 months at room temperature in a cool dry place. For prolonged shelf life the waxy surface should not be washed off unless it needs cleaning. During storage, dehydration may. induce sponginess, an unpleasant acidic flavor may induce and physical damage may occur. Other common defects during storage include small brown pits, seed germination, and change in flavor towards sourness. The green immature fruits can be packed into styrofoam ventilated trays or in wooden containers of 15 kg or more for long-distance transportation.
Quality improvement
Fully ripened or mature fruits are used for the preparation of petha (candy), sweet, or bari in Uttar Pradesh. In ash gourd, for petha preparation, big size (10-15 kg) oval to cylindrical fruits are required, while for household consumption small cylindrical cultivar (1-2 kg) is in demand. The quality requirement of ash gourd variety for petha processing is high pulp recovery, high content of dry matter, less crude fiber, high flesh diameter, and less seed with the linear arrangement in the fruit.
Value-addition
Several value-added products prepared from mature fruits are available in the market. In general, based on preparation techniques, petha is broadly classified as crystallized (plain petha) and preserved (Kashi Petha).
