Detailed Explanation of New Techniques for High-Quality and High-Yield Cultivation of Bitter Gourd

I. Overview
Bitter gourd (Momordica charantia L.), also known as balsam pear, bitter melon, and cool melon, among other names. It is named bitter gourd because its fruit has a unique bitter taste. It is a cultivated species in the genus Momordica of the Cucurbitaceae family, an annual climbing herbaceous plant.
Bitter gourd originated in tropical regions and is widely distributed in tropical, subtropical, and temperate zones. India, Japan, and Southeast Asia have a long history of cultivation. It was introduced to China around the early Ming Dynasty, and by the mid-Ming Dynasty it was already commonly cultivated in southern China. It is now grown throughout the country.
Bitter gourd is mainly consumed for its tender fruit, and the tender shoots, leaves, and flowers are also edible. The tender fruit is tender and crisp in texture, with a slightly bitter yet refreshing and pleasant taste. This unique flavor and mouthfeel has the effect of stimulating appetite. Ripe fruit has reduced bitterness and increased sugar content, but the flesh becomes soft and mealy, with somewhat inferior flavor. The blood-red pulp inside the ripe fruit has a bitter taste and delicate fragrance, is rich in nutrients, and is also edible. Bitter gourd is nutritious. According to nutritional analysis data, every 100 grams of fresh fruit flesh contains 0.08 mg of vitamin A, 0.07 mg of vitamin B1, 0.04 mg of vitamin B2, 84 mg of vitamin C, 0.3 mg of niacin, 0.9 g of protein, 0.2 g of fat, 3.2 g of carbohydrates, 0.6 g of inorganic salts, 18 mg of calcium, 29 mg of phosphorus, 0.6 mg of iron, 1.1 g of crude fiber, and 75.3 kilojoules of calories. Its vitamin C content is particularly prominent among cucurbit vegetables, being 14 times that of cucumber, 5 times that of winter melon, and 7 times that of tomato.
Bitter gourd is not only nutritious but also has high medicinal value. According to relevant sources, the roots, stems, leaves, flowers, fruits, and seeds of bitter gourd can all be used as medicine. It is cold in nature and bitter in taste, and clears summer heat, relieves inflammation, improves eyesight, and detoxifies. Pharmacological tests have shown that the physiologically active protein in bitter gourd can effectively enhance human immunity. The anti-cancer substances contained in bitter gourd have cancer-preventing and anti-cancer effects. The most medicinally valuable component of bitter gourd is a substance with a structure similar to insulin, which has effects similar to insulin and can lower blood sugar levels in the human body, making it an ideal health food for diabetic patients.
In China, the cultivation and consumption of bitter gourd are relatively common in Guangdong, Guangxi, Fujian, Taiwan, China, Hainan, Hunan, Jiangxi, Sichuan, Hubei, Yunnan, Guizhou, and other provinces and regions. In South China, it is planted in spring, summer, and autumn. In Hainan Province, production can be carried out year-round.
II. Growth and Development and Requirements for Environmental Conditions
1. Growth and Development
Seed germination stage: From seed germination to cotyledon unfolding, it takes 7 to 10 days at a temperature of 30 to 35 degrees C.
Seedling stage: From the first true leaf breaking through the heart to the appearance of tendrils (about 5 to 6 true leaves). At the optimum temperature of 20 to 25 degrees C, it takes about 25 days. In production, attention should be paid to preventing excessive vegetative growth of seedlings caused by high temperatures and excessive moisture. Flower bud differentiation has already begun during the seedling stage.
Vine elongation stage: From the emergence of tendrils from the seedling to the appearance of flower buds on the plant. The stems and vines begin to change from upright to prostrate growth. At temperatures above 20 degrees C, it takes about 15 to 20 days. At this time, flower buds differentiate and develop rapidly.
Flowering and fruiting stage: From the appearance of flower buds on the plant to the completion of harvest, it takes about 50 to 70 days or more.
2. Requirements for Environmental Conditions
Temperature: The optimum temperature for the seed germination stage is 30 to 35 degrees C; below 20 degrees C, germination is slow. The optimum growth temperature for the seedling stage is 20 to 25 degrees C; below 15 degrees C, growth is slow. The optimum temperature for the vine elongation stage and the flowering and fruiting stage is 20 to 30 degrees C; during this period, it can tolerate high temperatures of 35 to 40 degrees C. In the late flowering and fruiting stage, it can tolerate low temperatures of 10 to 15 degrees C. Different maturity varieties of bitter gourd have different temperature tolerances. Generally, early-maturing varieties are more tolerant of low temperatures, while mid- and late-maturing varieties are more tolerant of high temperatures.
Light: Sufficient light is required throughout the entire growth period, especially during the flowering and fruiting stage. With sufficient light, the fruit-setting rate is high, fruit development is fast, and quality is good.
Water: Bitter gourd requires a lot of water, especially during the flowering and fruiting stage, when stem and leaf growth and flowering and fruiting growth are rapid. If the water supply is insufficient, plant growth will be poor. However, bitter gourd is a crop that likes moisture but is not tolerant of waterlogging. After rain or irrigation, drainage should be carried out promptly.
Soil and nutrition: Bitter gourd is not strict about soil requirements, but its roots are afraid of waterlogging, so sandy loam soil with good drainage performance should be selected for cultivation. Bitter gourd has a long growth period and vigorous growth, and requires a large amount of fertilizer. Only by ensuring the application of sufficient nitrogen, phosphorus, and potassium fertilizers can a good harvest be achieved. In production, while applying sufficient base fertilizer, attention should be paid to topdressing at different growth stages. If fertilizer is insufficient, the fruit-setting rate will be low, stems and leaves will be weak, and the fruit will be small and of poor quality.
III. Types and Varieties of Bitter Gourd
(I) Types of Bitter Gourd
Bitter gourd types can be divided by fruit skin color into two types: green (dark green) skin bitter gourd and white skin bitter gourd. By fruit shape, there are 3 types: short conical, long conical, and long cylindrical. By fruit size, there are two types: large bitter gourd and small bitter gourd.
At present, most bitter gourd varieties cultivated in open fields belong to the large bitter gourd type. Courtyard cultivation and ornamental cultivation mostly use the small bitter gourd type. The main characteristics of large bitter gourd: the fruit is cylindrical, slightly pointed at both ends, generally 16 to 49 cm long and 5 to 8 cm in transverse diameter. The fruit contains relatively few seeds, mainly concentrated in the middle and lower parts of the fruit. When the fruit matures, it easily cracks open, and after cracking, the seeds fall out. The wart-like protrusions on the fruit surface are fine, dense, and attractive. The fruit color changes with different stages of fruit development and maturity. Generally, young fruit is dark green, at commercial maturity it becomes green, light green, or white, and at physiological maturity it all becomes red-yellow. Characteristics of small bitter gourd: the fruit is short spindle-shaped or round hammer-shaped, generally 6 to 12 cm long and about 5 cm in transverse diameter. The fruit skin color is either green-white or white. At physiological maturity, it is golden yellow. The flesh is relatively thin, the fruit contains more seeds, the bitterness is strong, and the yield is not high.
(II) Main Cultivated Varieties of Bitter Gourd
Bitter gourd is relatively commonly cultivated in Guangdong, Guangxi, Fujian, Taiwan, China, Jiangxi, Hainan, Sichuan, Hunan, and other provinces and autonomous regions south of the Yangtze River, and variety resources are abundant. In recent years, cultivation in the north has also increased. Through mutual introduction, domestication, and breeding, local varieties have been formed in various places.
1. Reyan No. 1 Youlü Bitter Gourd
A variety newly bred in 2005 by the Institute of Crop Germplasm Resources, Chinese Academy of Tropical Agricultural Sciences. Reyan No. 1 Youlü Bitter Gourd has vigorous plant growth and strong branching ability. The fruit is long conical, with a longitudinal diameter of 24 to 27 cm, a transverse diameter of 7.0 to 7.5 cm, and a flesh thickness of 1.2 cm. The flesh is sweet and crisp, with a slightly bitter taste. The single fruit weighs 400 to 500 g. The skin color is dark green and glossy. The fruit shape is attractive, with a flat shoulder and a bluntly rounded tip. The quality is excellent. The first female flower node is at nodes 10 to 16. The yield is 3000 to 4000 kg per mu. It has relatively strong cold tolerance, high resistance to powdery mildew, and moderate resistance to Fusarium wilt.
2. Reyan No. 2 Youlü Bitter Gourd
A variety newly bred in 2005 by the Institute of Crop Germplasm Resources, Chinese Academy of Tropical Agricultural Sciences. Reyan No. 2 Youlü Bitter Gourd has vigorous plant growth and strong branching ability. The fruit is long conical, 26 to 32 cm long, with a transverse diameter of 6.0 to 6.5 cm and a flesh thickness of 1.1 cm. The flesh is sweet and crisp, with a slightly bitter taste. The single fruit weighs 450 to 500 g. The skin color is dark green and glossy. The fruit shape is attractive, and the quality is excellent. The first female flower node is at nodes 10 to 15. The yield is 3000 to 4000 kg per mu. It is relatively resistant to powdery mildew and moderately resistant to Phytophthora blight.
3. Changbai Bitter Gourd
Also known as Zhuzhou No. 1 Bitter Gourd, bred by the Zhuzhou City Agricultural Science Research Institute, and cultivated throughout Hunan Province. The plant is vining, with strong growth vigor and strong branching ability. The leaves are palmately 5-lobed. The first female flower is borne at about node 17, after which 1 female flower appears in 2 to 3 consecutive nodes or every 3 to 4 nodes. The fruit is long cylindrical, 70 to 80 cm long, with a transverse diameter of 5.4 to 6.5 cm. The outer skin is green-white, densely covered with wart-like protrusions. The single fruit weighs 0.6 to 1.1 kg. The flesh is 0.8 to 1 cm thick, crisp and tender, slightly bitter, and of good quality. It is mid-maturing. It is heat-tolerant, fertilizer-tolerant, and strongly disease-resistant. It is suitable for open-field cultivation in spring and summer. The yield per mu is 3000 to 3500 kg.
4. Texuan Zhuzhou Changbai Bitter Gourd
Bred by the Hunan Provincial Vegetable Research Institute. Mid-maturing, high-yielding type. The plant grows vigorously and has strong branching ability. Both the main vine and side vines can bear fruit. The first female flower on the main vine is borne at nodes 10 to 12, after which 1 female flower is borne every 3 to 4 leaf nodes. The fruit is long strip-shaped, straw-white in color, about 60 cm long, with a transverse diameter of 6 cm. The single fruit weighs 0.6 to 0.8 kg. The flesh is crisp and tender, refreshing, and slightly bitter. It is heat-tolerant, fertilizer-loving, and moisture-tolerant. The yield per mu is 3800 to 4000 kg.
5. Dabai Bitter Gourd
Bred by the Horticulture Research Institute, Hunan Academy of Agricultural Sciences. It is cultivated throughout the south and has also been introduced in the north. The plant climbs and grows, with strong growth vigor. The fruit is long cylindrical, 60 to 65 cm long, with a transverse diameter of about 5 cm. The outer skin is white, with irregular fine and dense wart-like protrusions, and thick flesh. It has few seeds and excellent quality. The single fruit weighs 500 to 600 g. It is mid-maturing. It is heat-tolerant, moisture-tolerant, and disease-resistant. It is suitable for spring and summer cultivation.
6. Lanshan Dabai Bitter Gourd,
A local excellent variety bred in Lanshan City, Hunan Province. It has strong growth vigor and strong branching ability. The leaves are dark green and palmately 5-lobed. The first female flower is borne at nodes 10 to 12 on the main vine. The fruit is long cylindrical, 50 to 70 cm long, with a maximum length of up to 90 cm, and a transverse diameter of 7 to 8 cm. The outer skin is milky white, with large and dense wart-like protrusions on the surface, and glossy. The flesh is relatively thick, white, crisp and tender, and slightly bitter. The single fruit weighs 0.75 to 1.75 kg, with a maximum of more than 2.5 kg. It is mid-maturing. It is heat-tolerant and very strongly disease-resistant. It has wide adaptability and high yield.
7. Texuan Lanshan Dabai Bitter Gourd
A new variety bred in 1993 by the Hunan Provincial Vegetable Research Institute. Mid-maturing, high-yielding type. The plant has vigorous growth vigor and strong branching ability. Both the main vine and side vines can bear fruit. The main vine can reach 5 m in length. There are many female flowers and continuous fruit setting. The first female flower on the main vine is borne at nodes 10 to 12 of the main vine. The fruit is thick and long strip-shaped, light green-white, 50 to 60 cm long, with a transverse diameter of 7 to 8 cm. The single fruit weighs 0.7 to 1.5 kg. The flesh is crisp and tender, refreshing, and slightly bitter. It is heat-tolerant, moisture-loving, moisture-loving, moderately resistant to Fusarium wilt, and resistant to high-temperature and rainy weather. Generally, the yield per mu is 4000 kg.
8. Jiangmen Dading
A farm variety from Jiangmen City, Guangdong Province, famous for its large top, thick flesh, and sweetness amid bitterness. The plant is vining, with strong growth vigor and branching ability. The leaves are palmately 5- to 7-cleft. The first female flower is borne at nodes 8 to 14 on the main vine, after which 1 female flower is borne every 3 to 5 nodes. The fruit is short conical, about 20 cm long, with a shoulder width of about 11 cm. The outer skin is green, with relatively large wart-like protrusions. The flesh is about 1.3 cm thick, mildly bitter, and of excellent quality. The single fruit weighs 300 to 600 g. It is heat-tolerant, fertilizer-tolerant, and highly adaptable, but not waterlogging-tolerant. It can be planted in spring, summer, and autumn. The yield per mu is 1500 to 2000 kg, and generally spring cultivation gives higher yields.
9. Huashen Bitter Gourd
A local variety in Guangzhou City. The stems are vining, with strong branching ability. The leaves are nearly round and palmately 5- to 7-lobed. The first female flower is borne at nodes 6 to 12 on the main vine, after which 1 female flower is borne every 3 to 6 leaf nodes. The fruit is long conical, about 24 cm long, with a shoulder width of about 7 cm. The fruit surface has neat longitudinal groove stripes and alternating wart-like protrusions. The outer skin is green and glossy. The flesh is about 1.2 cm thick, mildly bitter, and of good quality. The single fruit weighs 250 to 300 g. It is relatively heat-tolerant and highly adaptable. The fruit is relatively firm and suitable for transport. The yield per mu is 1000 to 1500 kg.
10. Penang Bitter Gourd. A variety introduced from Thailand. The plant has strong growth vigor. The first female flower begins to be borne at about nodes 9 to 23 on the main vine, after which 1 female flower is borne every 3 to 6 nodes. The fruit is long conical, 20 cm long, with a shoulder width of 8 cm. The single fruit weighs 400 to 500 g. The fruit surface has neat longitudinal grooves, stripes, and alternating wart-like protrusions. The skin color is green and glossy. The flesh is fine and slightly bitter. This variety is heat-tolerant, disease-tolerant, delicately fragrant and slightly bitter, crisp and tender, and after stir-frying or boiling it has a sea cucumber flavor, with a unique flavor.
11. Cuilü No. 1. A first-generation hybrid bitter gourd bred by the Vegetable Research Institute, Guangdong Academy of Agricultural Sciences. The fruit is medium conical, 16 to 18 cm long, with a shoulder width of 8 to 10 cm and a flesh thickness of 1.2 cm. The single fruit weighs 0.4 kg. The wart ridges are thick and straight, and the fruit color is emerald green and glossy. The fruit has an attractive appearance and good marketability. This variety is early-maturing, relatively cold-resistant, shade-tolerant, and resistant to powdery mildew and downy mildew. The yield is relatively high, generally 30000 kg per hectare.
12. Xingshu Chunyu Bitter Gourd. Main vine fruiting is dominant. The first female flower node is at nodes 8 to 10, with good node-setting. The fruit is 28 to 30 cm long, about 5 to 6 cm thick, with a flesh thickness of 1.1 cm. It is oil-green, with a rod-shaped fruit and protruding warts. It has good marketability. The single fruit weighs about 300 g. It is slightly bitter and widely adaptable. Main vine fruiting is dominant. The first female flower node is at nodes 8 to 10, with good node-setting. The fruit is 28 to 30 cm long, about 5 to 6 cm thick, with a flesh thickness of 1.1 cm. It is oil-green, with a rod-shaped fruit and protruding warts. It has good marketability. The single fruit weighs about 300 g. It is slightly bitter and widely adaptable.
13. Xingshu Chunyan Bitter Gourd. Main vine fruiting is dominant. The first female flower node is at nodes 7 to 9, with good node-setting. The fruit is 30 cm long, about 4 to 5 cm thick, with a flesh thickness of 1.0 cm. It is green, with a rod-shaped fruit and protruding warts. It has good marketability. The single fruit weighs about 420 g. It is slightly bitter and widely adaptable.
14. Suixin No. 2 Bitter Gourd. Suixin No. 2 has vigorous growth vigor and strong branching ability, with good heat tolerance. It can be planted in summer and autumn in various parts of Guangdong, Guangxi, Fujian, and elsewhere, and its economic traits are superior to the currently produced varieties Dalang, Xialei, Yingyin, and others. In addition to being suitable for local sales, the product can also be sold to Hong Kong, China, Macao, China, and other places in summer and autumn. It performs as follows: the fruit skin color is green and glossy; the wart-like protrusions on the fruit surface are in thick stripe form; the fruit shape is long conical and attractive, 15 to 20 cm long; the fruit shoulder width is 5 to 7.5 cm; the flesh thickness is more than 1 cm; the sweet-bitter taste is moderate; the flesh is crisp and tender with a good mouthfeel; the single fruit weighs 300 to 500 g; and it is relatively early-maturing. When planted in summer and autumn, it takes 45 to 50 days from sowing to first harvest. The first female flower node is borne at leaf nodes 15 to 20 on the main vine. Both the main vine and side vines can set fruit, and it has good yielding ability. When planted in summer and autumn, the yield per mu is 1100 to 2000 kg.
　　
IV. High-Yield Cultivation Techniques for Bitter Gourd
1. Cultivation season: Bitter gourd can be cultivated year-round in Hainan Province. If grown as off-season cultivation, sowing from September to December is appropriate.
2. Raising strong seedlings: Generally, the seed rate per mu is half a jin. Bitter gourd roots are prone to suberization and have weak regeneration ability, so nutrient pots or paper bags are generally used for seedling raising, and transplanting is done when the seedlings have 3 to 4 true leaves. If the field seedling method is used, transplant as early as possible when the seedlings have 1 to 2 true leaves. If transplanting is too late, many roots are damaged, and the seedlings are not easy to survive after transplanting. The main seedling-raising methods are as follows:
Seed treatment: The seed coat of bitter gourd is relatively thick and hard in texture, making germination difficult. To make bitter gourd germinate as quickly as possible, you can gently crack a small opening at the seed germination pore, then scald the seeds with warm water at 55 degrees C while stirring constantly. When the water temperature drops to 30 degrees C, soak the seeds for 10 to 12 hours. After removing them, wrap them in a clean wet towel or gauze and place them under conditions of 30 to 35 degrees C for germination. Generally, they will sprout in 2 to 3 days. Once most seeds have sprouted, they can be sown.
Preparation of nutrient soil: Generally, use 6 parts field soil that has not grown vegetables and 4 parts fully decomposed horse manure, pig manure, and wheat or rice straw.
Sowing: Fill the nutrient pots with nutrient soil and arrange them neatly in the seedbed. Water thoroughly. After the water seeps down, place the germinated seeds flat in the center of the nutrient pots and cover with soil to a thickness of 1 cm. After sowing, cover the seedbed with a layer of plastic film to help increase temperature and retain moisture in the seedbed. Remove the film promptly after seedlings emerge.
Seedbed management: During the seed germination stage, the daytime temperature should be maintained at 30 to 35 degrees C, and the nighttime temperature at above 20 degrees C. When the plant grows to 2 to 3 true leaves, flower bud differentiation begins. Low temperature and short-day conditions during the seedling stage are favorable for female flower differentiation. In particular, low nighttime temperatures result in more female flowers and can lower the node at which the first female flower appears. During the seedling stage, when the surface soil is slightly dry, water on sunny days to prevent the surface soil from drying out. To make the seedlings sturdy, during the seedling stage you can spray a 0.3% potassium dihydrogen phosphate or urea aqueous solution every 7 to 10 days, for 2 to 3 consecutive sprays. About 7 days before transplanting, stop watering and harden the seedlings. Generally, the standard for strong seedlings is: seedling height 20 cm, 4 leaves and 1 heart, cotyledons intact, leaves thick, color deep green, stems thick and strong, root system white and well developed, and no pests or diseases.
3. Field transplanting
Land preparation: Bitter gourd has a long growth period and a large fertilizer requirement, so sufficient base fertilizer should be applied while preparing the land. Generally, after the land is fully plowed, harrowed fine, and leveled, beds are made with a height of 20 to 30 cm. Apply 2000 to 3000 kg per mu of fully decomposed high-quality farmyard manure (pig, cattle, and sheep manure, human waste, etc.), plus 30 kg of superphosphate and 30 to 50 kg of compound fertilizer.
Planting density: For high-density cultivation, plant about 900 to 1200 plants per mu; for low-density cultivation, plant 300 to 400 plants per mu. To increase early yield, high-density cultivation can be used, with thinning of plants in the middle and late stages, planted in single rows or double rows.
Transplanting: When planting seedlings, break up the soil around the planting hole finely, then remove the bag from the seedling and place the seedling with its soil ball into the hole. Cover with soil and press lightly. The soil covering height should be such that the cotyledons are exposed above the ground. After transplanting, water thoroughly to settle the roots.
Trellising: The main cultivation methods for bitter gourd include hedge trellis, net shed trellis, arched shed trellis, flat shed trellis, and hedge-shed trellis.
Hedge trellis. Hedge trellises are divided into A-shaped hedge trellises and net hedge trellises. A-shaped hedge trellises were used more in the past and are used less now. Every 3 to 4 m, set 1 post with a height of 2 to 2.5 m, and stretch fishing net between the posts, with a mesh side length of 30 to 40 cm. The characteristics of this method are that the trellis is simple to build, management is convenient, and the vines grow well, basically requiring no vine guiding. However, after entering the peak growth period, ventilation is poor. It is suitable for high-density cultivation.
Net shed trellis. On both sides of the shed, set 1 post every 3 to 4 m with a height of 2.5 m. Stretch iron wire between the tops of the posts, lay the fishing net on top, and tie it to the iron wire. The mesh side length is required to be about 30 to 40 cm. If too small, it easily traps fruits and leaves; if too large, the vines cannot climb well. Each seedling also needs a string to guide the vine upward. In Yacheng, Sanya, Hainan, growers mostly use this kind of trellis for cultivation. The cost of this trellis is relatively high.
Arched shed trellis. Tied with thin bamboo strips, with a shed top height of about 2.5 m. In Tunchang, Hainan, this kind of trellis is mostly used. The characteristics of this trellis are that it is sturdy, has good ventilation, and has the best lighting, but it requires more labor.
Flat shed trellis. The height is between 2.0 and 2.5 m. This kind of shed has relatively good ventilation and lighting, but it is not as convenient to operate as the arched shed trellis and is not as sturdy as the arched shed trellis.
House-shaped shed trellis. This method is used more in Baoting, Hainan, such as in Jiamao Town, Shiling Town, Nanmao Farm, and others. The shed width is 3.5 to 4.0 m, and the plant spacing is 0.8 to 1.0 m. In the middle and late stages, thin out 1 of every 2 plants.
After bitter gourd vines fall over, vine guiding, vine tying, and pruning of branches should be carried out promptly. For low-density cultivation, leave 2 to 3 strong side vines at the base and remove the rest. For high-density cultivation, remove all side vines below 1 m. In principle, retain side vines above 1 m, but appropriately thin them according to the situation.
4. Field management:
Intertillage and weed control: After transplanting and survival, carry out the first intertillage to a depth of 7 to 10 cm. After half a month, carry out the second intertillage to a depth of about 5 cm. Intertillage can loosen the soil layer, facilitate drainage during the rainy season, and also control weeds. After trellising, it is not suitable for operation, so no more intertillage is done, and mainly hand weeding is carried out. On the one hand, this improves field ventilation and light transmission conditions, and it can also prevent weeds from competing with bitter gourd for water and fertilizer. The base of bitter gourd near the ground easily grows adventitious roots when the soil is moist. To increase the absorption area of the bitter gourd root system, each intertillage should be combined with hilling.
Water management: Bitter gourd has a large growth volume and a very large water requirement. After planting, water as appropriate. If sunny and high-temperature weather occurs after planting, in order to lower soil temperature, reduce leaf evaporation of seedlings, and keep the soil moist, water in the early morning or evening. After the seedlings survive, the amount of watering can be reduced, but the soil should still be kept moist. When entering the full fruiting stage, if it is sunny with no rain, irrigate once every 3 to 4 days. Irrigation time should be before 8 a.m. or after 4 p.m. Generally, furrow irrigation is used. After irrigation, drain promptly, and it is appropriate for the bed surface to be moist. After rain, pay attention to promptly cleaning the furrows and draining water. Prevent water accumulation.
Topdressing: In the early stage, bitter gourd has a small growth volume, so topdressing should be light. In the later stage, vines, leaves, flowers, and fruits grow simultaneously, requiring a large amount of fertilizer, so the topdressing concentration should also be increased. After direct seeding and emergence or after transplanting and survival, begin topdressing combined with watering using 10% human manure and urine or a 0.3% urea aqueous solution to promote root growth. After 6 to 7 days, apply a 0.3% urea aqueous solution to promote vine elongation. Before trellising, apply another 0.3% urea aqueous solution. After trellising, apply 10 kg of compound fertilizer and 5 kg of urea per mu. After mixing the fertilizers evenly, apply them in spots 10 to 15 cm from the base of the plants. When the first female flower opens, topdress with about 20% human manure and urine or a 0.3% urea aqueous solution to promote young fruit growth. After fruit setting, alternate topdressing and watering, keeping topdressing once a week, with a concentration of about 30% decomposed human manure and urine being appropriate. After the first batch of fruits is harvested, apply 5 kg of urea and 10 kg of compound fertilizer per mu in spots 12 to 15 cm from the base of the plants. In the middle and late stages of flowering and fruiting, combined with irrigation, apply 15 to 20 kg of compound fertilizer per mu in spots to promote vine and leaf growth and extend the harvest period. At the same time, carry out foliar topdressing. On sunny evenings, spray the leaves with a 0.2% urea and 0.3% potassium dihydrogen phosphate aqueous solution.
Plant adjustment: After the vines begin to climb, guide the vines onto the trellis promptly, and at the same time tie the vines. Tie the first time when the vine is 30 cm long, and thereafter tie once every 4 to 5 nodes. Vine tying should be done after 9 a.m. to prevent vine breakage. Combined with vine tying, pruning can be carried out. For off-season bitter gourd, the main vine should be the main bearer of fruit. Generally, under the trellis, select and retain only 1 to 2 healthy side branches and let them grow, and remove other side vines promptly.
In the late fruiting stage, the middle and lower leaves begin to age and gradually turn yellow. To improve ventilation and light transmission conditions and reduce pest and disease damage, remove the aged yellow leaves in the middle and lower parts.
5. Harvesting: For off-season bitter gourd, it takes about 50 to 55 days from sowing to first harvest. From flowering to maturity takes about 10 to 16 days. Harvest timing should be grasped well. It is appropriate to harvest when the wart-like protrusions on the fruit have expanded and the top of the fruit begins to shine. If harvested too tender, the bitterness is strong, quality is poor, and yield is also low. If harvested too ripe, the flesh becomes soft and is not resistant to storage and transport. Because bitter gourd flowers and sets fruit multiple times, harvesting should be frequent. During the full fruiting stage, harvest once every 2 to 3 days; otherwise, it will affect the growth and development of the lower fruits. Harvesting should preferably be done before the sun comes out, cutting from the base with scissors. Harvesting at noon or in the afternoon is not appropriate; otherwise, the harvested bitter gourd easily turns yellow and is not resistant to storage and transport. During harvesting, handle gently and place gently to prevent mechanical damage.
V. Pest and Disease Control of Bitter Gourd
(I) Bitter Gourd Diseases and Their Control
1. Powdery mildew:
Symptoms of damage: Mainly damages leaves. At the early stage of the disease, nearly round small white powdery spots appear on the front or back of the leaves, mostly on the back of the leaves. Later, the lesions gradually expand and become large white powdery areas with indistinct edges. In severe cases, the leaves become yellow, withered, and brittle, but generally do not fall off. The white powdery substance gradually turns gray-white, and finally the entire leaf becomes yellow-brown and dried up. The disease mostly starts from the middle and lower leaves and gradually spreads to the upper leaves.
Disease conditions: The pathogen of this disease is an ascomycete, an obligate parasite. The diseased seedlings overwinter as mycelium or cleistothecia on the host or on diseased residues, and can also overwinter on crops such as greenhouse cucumber. The pathogen is mainly spread by air and flowing water. The epidemic temperature of this disease in the field is 16 to 24 degrees C. It has a wide range of adaptation to relative humidity. When the air humidity is 45% to 75%, the disease develops quickly. When it exceeds 95%, disease development is clearly inhibited. Generally, in years with relatively low rainfall, the disease is mild. When there are continuous cloudy days and muggy weather, the disease develops rapidly. Excessive vegetative growth of plants, overly dense vines and leaves, and poor ventilation and light transmission easily lead to large outbreaks of powdery mildew.
Control measures: (1) Strengthen cultivation management. Attach importance to raising strong seedlings, practice reasonable dense planting, prune branches and leaves in time, improve ventilation and light transmission conditions, make plants grow vigorously, and improve disease resistance. Base fertilizer should be supplemented with phosphorus and potassium fertilizers, and excessive application of nitrogen fertilizer should be prevented during the growth period.
(2) Physical control. Use 27% higher fatty alcohol emulsion at 80 to 100 times dilution, spray on leaves at the early stage of disease to form a thin film, which can not only prevent pathogen invasion but also create oxygen-deficient conditions to kill powdery mildew fungi. Generally, spray once every 5 to 6 days, for 3 to 4 consecutive sprays.
(3) Biological control. Spray 2% agricultural antibiotic 120 aqueous solution, then spray again every 6 to 7 days, with a control effect of more than 90%.
(4) Chemical control. The agents that can be sprayed alternately include: 15% triadimefon wettable powder at 1500 times dilution, 30% triflumizole wettable powder at 1500 to 2000 times dilution, 40% sulfur·carbendazim suspension concentrate at 500 to 600 times dilution, 50% sulfur suspension concentrate at 250 to 300 times dilution, 50% amobam aqueous solution at 1000 times dilution, 47% kasugamycin plus copper wettable powder at 600 to 800 times dilution, and 77% copper hydroxide wettable powder at 500 to 700 times dilution. In protected cultivation, fumigation with chlorothalonil or sulfur smoke agents can control both downy mildew and powdery mildew.
The technical points of chemical control are: early prevention, thorough spraying, and large water volume. When spraying, spray evenly on the middle and lower old leaves and the undersides of leaves. At the early stage of disease, spray once every 7 to 10 days, for 2 to 3 consecutive sprays, which can achieve relatively good control effects.
2. Phytophthora blight
Symptoms of damage: Bitter gourd Phytophthora blight mostly shows symptoms before flowering. Both stems and fruits can be infected. When leaves are infected, they first lose luster. At the early stage, the lesions are dark green water-soaked spots, irregular in shape, with indistinct edges. When humidity is high, a very thin layer of white mold can be seen growing on the diseased area; when dry, it appears blue-white and easily breaks. Petioles and vine nodes show dark green water-soaked soft rot, and the affected parts easily constrict. When fruits are damaged, dark green sunken lesions appear. When humidity is high, the fruits quickly become soft and rot, and sparse white mold grows on the affected area, with a foul odor.
Disease conditions: It is a fungal disease caused by Phytophthora. The pathogen overwinters in the soil as mycelium, chlamydospores, and oospores along with diseased plant residues. The pathogen on the lesions spreads through watering, rain splash, and air movement. The optimum temperature for the pathogen to cause disease is 27 to 31 degrees C, with a maximum of 37 degrees C and a minimum of 5 degrees C. The release of zoospores from sporangia requires water. Low temperature and continuous rain or high temperature and high humidity are both favorable for pathogen infection and disease development, and the incubation period is short, only 3 to 4 days. It usually occurs in August and September. Drought followed by rain, or heavy irrigation as fruits enter the growth stage, causing a sudden increase in soil water content, easily causes disease. The disease is severe in low-lying fields, fields with poor drainage, and continuous cropping fields.
Control measures
(1) Agricultural control: Implement crop rotation of more than 3 years. Use plastic film mulching and high-ridge (bed) cultivation to reduce pathogen splash from the ground. Irrigate reasonably and control field humidity. Appropriately control watering during the rainy season, drain water promptly after rain, and ensure the ground dries after rain. Water promptly in case of drought. When watering, strictly prohibit flood irrigation, and it should be done on sunny afternoons or evenings. Apply more organic fertilizer to promote vigorous plant growth, deep roots, and luxuriant leaves, and improve resistance. Carry out plant adjustment in time to prevent overly dense growth and poor ventilation and light transmission. Remove diseased leaves at any time and burn them.
(2) Chemical control: Select 25% metalaxyl wettable powder at 800 to 1000 times dilution, 80% zineb wettable powder at 600 to 800 times dilution, 64% oxadixyl plus mancozeb wettable powder at 500 to 600 times dilution, 40% fosetyl-aluminum wettable powder at 300 to 400 times dilution, 80% mancozeb wettable powder at 500 to 600 times dilution, 72.2% propamocarb aqueous solution at 400 to 600 times dilution, 50% copper potassium phosphite wettable powder at 600 times dilution, and other agents for alternate spraying, once every 5 to 10 days, for 3 to 4 consecutive times. Spraying should be thorough and meticulous, and all leaves, fruits, and nearby ground should be sprayed.
3. Downy mildew. Both the seedling stage and adult plant stage can be damaged. It mainly damages leaves, stems, tendrils, and flower stalks. When disease occurs at the seedling stage, irregular chlorotic yellow withered spots appear on the upper side of the cotyledons. When moist, a gray-black mold layer appears on the underside of the leaves. In severe cases, the cotyledons turn yellow and dry up. When disease occurs at the adult plant stage, it mostly starts from the lower leaves and gradually spreads upward. At the beginning of the disease, water-soaked light green or yellow small spots appear on the upper side of the leaves, then gradually expand, changing from yellow to light brown, and are limited by leaf veins to form polygonal lesions. On the underside of the leaves at the lesion sites, a purple-gray mold layer is produced. Under moist conditions, the mold layer thickens and appears black. In severe cases, the lesions connect into patches, the entire leaf becomes yellow-brown, dries up and curls, and all plant leaves die.
Chemical control. At the early stage of disease, use 25% metalaxyl wettable powder at 800 to 1000 times dilution; or 40% fosetyl-aluminum wettable powder at 300 times dilution; or 75% chlorothalonil wettable powder at 600 to 800 times dilution; or 65% zineb wettable powder at 400 to 500 times dilution; or 58% metalaxyl plus mancozeb at 600 times dilution; or 64% oxadixyl plus mancozeb at 400 times dilution. Use one of the above agents, once every 7 to 10 days, for 3 to 6 consecutive sprays.
4. Melon fruit fly. Melon fruit fly is also known as the “needle bee”, melon maggot, and so on. This insect belongs to the family Tephritidae of the order Diptera. It mainly damages with larvae. First, the adult inserts its ovipositor into the epidermis of young melons to lay eggs. After the larvae hatch, they bore into the fruit flesh to feed. The damaged melon first turns yellow locally, and then the whole melon rots and becomes foul-smelling. This causes the plant to drop a large number of fruits. Even if the melon does not rot, the puncture site has gummosis, is deformed and sunken, the fruit skin hardens, and the melon taste becomes bitter and astringent and the quality declines.
Control methods: First, promptly remove damaged melons, spray them with chemicals, and bury them deeply. Second, in severe cases, bag the young melons to prevent adults from laying eggs. For chemical control, during the peak adult occurrence period, use poisoned bait to trap and kill adults. You can use 40 parts banana peel + 0.5 part 90% trichlorfon crystal + 1 part essence, or use 1.8% abamectin oil paste at 1500 times dilution + lüshadan at 1500 times dilution (4.5 m EC) for control, spraying twice consecutively, which also gives relatively good results. Or spray plants with 50% dichlorvos emulsifiable concentrate at 1000 times dilution and 2.5% deltamethrin at 3000 times dilution, once every 3 to 5 days, for 2 to 3 consecutive sprays. This has a good effect on controlling adults. Bag young melons with paper bags for protection to prevent adults from laying eggs. Remove damaged melons and destroy them. Flypaper can also be hung between rows, which also has a certain effect.
5. Melon borer. This borer belongs to the family Pyralidae of the order Lepidoptera. It damages plants with larvae. In the early larval stage, it feeds on the leaf mesophyll on the underside of leaves, appearing as gray-white spots. After the third instar, it spins silk to join leaves or tender shoots together and hides inside to feed, causing leaves to have holes or notches. In severe infestation, only leaf veins remain. The larvae often bore into melons and feed on the flesh, affecting yield and quality.
Control methods: Clean the garden of residual plants and fallen leaves to eliminate overwintering pupae and reduce the source of insects. During the larval stage, spray plants with 20% fenvalerate at 3000 times dilution, or 50% malathion at 1000 times dilution, for high control effectiveness.
6. Cutworms. Cutworms belong to the family Noctuidae of the order Lepidoptera. There are many species of cutworms. Three are common in China: the black cutworm, the yellow cutworm, and the large cutworm. Among them, the black cutworm is a worldwide major pest and is the most widely distributed.
Poisonous grass bait trapping: Use 50 g of 90% trichlorfon, evenly mix with 30 to 40 kg of chopped fresh grass, add a small amount of water, and scatter near the vegetable field in the evening to trap and kill larvae.
Chemical control. For cutworm larvae before the third instar, you can use: 2.5% trichlorfon powder at 22.5 to 30 kg per hectare for dusting; or add 150 kg of fine soil to make poisonous soil and scatter it around the plants; or use 80% trichlorfon wettable powder at 1000 times dilution; or use 50% phoxim emulsifiable concentrate at 800 times dilution; or use 20% fenvalerate emulsifiable concentrate at 2000 times dilution for ground spraying. When the insect age is relatively large, you can use: 50% phoxim emulsifiable concentrate; or 80% dichlorvos emulsifiable concentrate at 1000 to 1500 times dilution for root irrigation to kill larvae in the soil.
7. Melon aphid. Melon aphid is also called cotton aphid, commonly known as honey insect, greasy insect, and so on. It belongs to the order Homoptera and the family Aphididae.
Adults and nymphs of the melon aphid parasitize the undersides of host leaves or tender shoots and use their mouthparts to pierce and suck sap. They especially like to gather on tender leaves and tender stems to feed, causing melon leaves to shrink, become deformed, and curl toward the underside. After plants are damaged, growth and development stagnate or slow down, reducing yield and quality. The melon aphid is also the main transmission vector of viral diseases. Viral diseases are currently one of the main diseases causing total crop failure and yield reduction in cucurbit vegetables. Therefore, melon aphid damage can cause reduced yield in mild cases and total crop failure in severe cases. Melon aphids also excrete honeydew, contaminating leaves and products and reducing product quality.
At present, aphid control is mainly chemical control. In chemical control, the principle of early prevention should be followed. Commonly used agents include: 50% pirimicarb wettable powder or water-dispersible granules at 2000 to 3000 times dilution. This agent has a special effect on vegetable aphids and does not harm natural enemies; or 40% dimethoate emulsifiable concentrate at 1000 to 1500 times dilution; or 70% menazon wettable powder at 2500 times dilution, and so on. Vegetable aphids easily develop resistance to pyrethroid pesticides, so they should be used with caution or mixed with other pesticides. Commonly used ones include: 2.5% deltamethrin emulsifiable concentrate at 3000 to 4000 times dilution; or 10% cypermethrin emulsifiable concentrate at 2000 to 6000 times dilution. Spray the above agents. You can also use 1.8% abamectin oil paste at 1500 times dilution plus 10% imidacloprid wettable powder at 1500 times dilution for control.