Introduction
Okra (Abelmoschus esculentus) or lady’s finger is considered an important vegetable crop of the tropical and sub-tropical regions of the world. It is popular in India, Nigeria, Pakistan, Cameroon, Iraq, and Ghana. India ranks first in the world with a production of 5.78 Mt (72% of the total world production) of okra from over 0.498 m ha land. Okra is available in India throughout the year and its products can be tailored according to the demand. After the onion, okra has the major share in revenue generation through the export of fresh vegetables. Andhra Pradesh, West Bengal, Bihar, Gujarat, Odisha, Jharkhand, and Maharashtra are the leading okra-producing states in India.
The edible fruit is valuable for a very good supplement of proteins, vitamins, and minerals in diets of people from the developing countries, where they depend on cereals crops, which are lacking them. Dry seeds of okra contain 18 to 20% of oil and 20 to 30% crude protein. Roasted and ground seeds find their use as a coffee substitute.
Climate and soil Requirement for Okra Cultivation
Okra is a warm-season vegetable crop mostly grown in a tropical and sub-tropical climate. It requires a long growing period of about 4 to 6 months with high temperature, humidity, and light intensity depending upon climatic conditions. Hot and humid weather is suitable for the growth of okra. It is most sensitive to frost and requires long frost-free periods for seed production. The seed does not germinate below 17°C. The optimum temperature requirement for growth, flowering, and fruiting are 24 to 28°C. Temperature higher than 42°C may cause flower drop. On the other hand, high night temperature can increase plant height in the majority of the present cultivars. Most of the okra cultivars require short photoperiod for floral bud initiation, however, day-neutral and long-day genotypes are also available. During summer, it is always desirable to maintain a temperature range of 30 to 35°C for improved pollination and subsequent seed setting. Adjustment of climatic factors helps in taking at least one (summer) crop in hills, 2 or even 3 (summer, Kharif, and late Kharif) crops in the east, west, and north Indian plains and almost year-round cultivation under moderate climate in south India.
The okra can be grown in varied types of soils but it, perform, better in friable and lighter soils ranging from sandy loam to loam. It gives good crops in heavier soils too with efficient drainage facilities during the rainy season. Sandy-loam to loam soils rich in organic matter and fair in water retention capacity is best suited during summer. A pH of 6.0 to 6.8 is ideally suited. However, the okra variety Pusa Sawani has some tolerance to salts. All soils need to be pulverized, moistened, and enriched with organic matter before sowing.
Varieties of Okra
Important commercially cultivated varieties in different parts of the country are described here.
Arka Abhay: Plants and fruits resemble Arka Anamika in appearance. Tolerant to fruit-borer. May suit pruning to tame the plant for a ratoon crop.
Arka Anamika: Plants upright (100-105 cm), Resistant to yellow vein mosaic virus, and open and slightly pigmented on stems, petioles, and lower leaves. Fruits are dark green with 5 prominent ridges and a comparatively less smooth surface. Takes 50 days (6th node) to first flowering and 55 days to first pick of tender marketable fruits. An excellent yielder in the south but with a lower performance in north India. It is resistant to yellow vein mosaic, yielding 125 q/ha.
Azad Kranti: Plants fast-growing, occasionally branched, and with sparse pigmentation. Fruits green, smooth, shiny, long, 5 ridged with a long beak, leaves are green, normally lobed. Tolerant to yellow vein mosaic virus. The yield potential is 125 q/ha. It is suitable for cultivation in spring, summer.
Co 1: Plants tall with 6-8 branches. Leaves are light green, medium-sized, and deeply lobed. Petioles are longer (around 24 cm). Fruiting starts from the 5th node. Fruits glossy, slender, 5 ridged, scarlet red color, non-persistent on cooking, an average 20 fruit/plant. Has field tolerance to yellow vein mosaic virus but is susceptible to fruit borer and powdery mildew.
Gujarat Bhindi 1: Plants grow to 60 cm in spring-summer and 90 cm in Kharif. With purple tinge on stem Leaves broad, dark green, with purple tinge on veins. Takes 55-60 days to first pick. Fruiting starts from a 4th-5th node. Fruits 5 ridged, tender, 14-15 cm long, and 6-7 cm in girth. Yield 70q/ha.
Hisar Unnat: Its first picking may be taken in 46-47 days. It is a high-yielding (120-130q/ha green fruits) variety. Plants are medium tall with short internodes, producing 3-4 branches. The petal base is pigmented from the inner side only. Fruits green, attractive, 5 ridged, 15-16 cm long on full maturity. Suitable for growing during summer as well as the rainy season.
Kashi Kranti: An early, medium-tall (100-115 cm) variety with short internodal length. First flowering 38-42 days after sowing. Each plant has 18 to 20 fruits of dark green color. The length and diameter of the fruit are 8 to 10 cm and 1.8 cm, respectively, at the marketable stage. Fruits available 45 to 95 days after sowing, yield 140-150 q/ha.
Kashi Lila (IIVR 11): Plants of medium height (110) to 130 cm). Flowering starts 30 to 34 days after sowing. Suitable for cultivation during the rainy season and summer as an early crop due to low-temperature tolerance. Fruits have five ridges, green and 13 to 15 cm long. It gives a yield of 150 to 170 q/ha.
Kashi Pragati (VRO 6): Plants tall (130-175 cm), with 1-2 effective branches, flowering appears between 36 and 38 days after sowing on 4th node during the rainy season and 3rd node during summer. Fruits 8 to 10 cm in length at the marketable stage, 23 to 25/plant. Yield 150 – 160 q/ha in the rainy season and 130-140 q/ha in the summer.
Kashi Satdhari (IIVR 10): Plant height 130-150 cm with 2-3 effective branches. Flowering starts between 42 and 43 days after sowing at 3rd to 4th nodes. Each plant bears 18-25 fruits with seven ridges, length 13 to 15 cm at the marketable stage. Yield 110-140 q/ha.
Kashi Vibhuti (VRO 5): Plants dwarf, 60 to 70 cm during rainy and 45 to 50 cm during summer. Bears 2 to 3 branches with short internodal length. Flowering starts on 4th to 5th nodes 38 to 40 days after sowing. Each plant bears 18 to 22 fruits of 8 to 10 cm length at marketable stages. Yield 170 to 180 q/ha.
Parbhani Kranti: Plants tall, single-stemmed with dark green foliage. Leaves are deeply lobed appearing like cut leaves towards the plant’s apex. The first flush becomes ready 55 days after sowing. Fruits smooth, dark green, tender, slender, 5-ridged with a long beak. Average green fruit yield varies from 85-90 q/ha during spring-summer to 115 q/ha during the rainy season.
Punjab 7: Plants medium tall with splashes of purple pigmentation present on the stem. Leaves deeply lobed up to the base of the petiole and margins less serrated. The basal portion of the petiole is deeply pigmented. Leaves, stems, and petiole are sparsely hairy. Fruits are medium long, green tender, and five ridged. Fruit tip slightly furrowed and blunt. Average yield 125 q/ha. It can be sown from February to March as well as in June-July.
Punjab 8: Plants medium tall with splashes of purple pigmentation present on the stem. Leaves deeply lobed and less serrated. Leaves, stems, and petioles are less hairy. Fruits thin, long, dark green, and five ridged. Resistant to yellow vein mosaic virus and tolerant. to jassid and borer. Suitable for processing. The average marketable yield is 140 q/ha. Suitable for February March as well as June-July sowing.
Punjab Padmini: Plants are taller than those of Pusa Sawani and with a purple tinge on the stem and petiole, leaves deeply lobed and hairy, fruits quick-growing, dark-green, thin, long, five ridged and remain tender for a longer period. The low intensity of virus symptoms appears only on the new shoot growth quite late in the season. Ready for first picking in 60 days. High yielding with an average yield of 125 q/ha. Suitable for sowing in the spring and rainy seasons.
Pusa A 4: Plants dark green with sparse pigmentation (occasional) on stems and petioles with a usually single stem having short internodes (2-4 cm). Leaves broad, medium lobed. Fruits 5 ridged, attractive, dark green, 12-15 cm long having excellent shelf-life. Resistant or tolerant to aphids and jassids and least preferred by shoot and fruit borer. In summer yield 100-120 q/ha, Kharif and late Kharif crop 175 q/ha.
Pusa Makhmali: Plants hairy, tall, erect, less branched with palmate and hairy leaves. A 5-ridged cultivar with excellent quality fruit. Fruits light green, tapered, attractive, and 12 to 15 cm long, the yield potential 80 to 100 q/ha. It is suited for cultivation in hills and virus-free regions (spring-summer in north India and rainy season in south India).
Pusa Sawani: It needs 45 to 50 days from sowing to first picking. The first fruit is borne on the 6th to 8th node. Upper leaves are deeply lobed. It is suitable for cultivation in both spring to summer Kharif day-neutral and less sensitive to temperature fluctuations. It has very wide adaptability. In hills, it can be sown from April to May depending upon the altitude, while in plains, a virus-free period is better suited (spring-summer in the north). It yields is 120-125 q/ha.
Shitla Uphar: Plants medium tall, height 110 to 130 cm, flowering starts 38 to 40 days after sowing at 4 to 5 nodes. Fruits green, 11 to 13 cm long at the marketable stage, and yield 150 to 170 q/ha.
Varsha Uphar: Plants medium tall with short internodes. Take 46-47 days to first pick. Fruits are smooth, dark green, attractive with long tapering tips measuring 18-20 cm on full maturity. Owing to the fast growth of fruits, harvesting on alternative days is recommended. Prolific bearer with an average fruit yield of 100 q/ha. Resistance to yellow vein mosaic virus and field tolerance to leafhoppers.
Hybrids
JNDOH 02-2: Plants 155-160 cm in height. First flowering appears 42-43 days after sowing. Each plant has 23 to 25 fruits; fruits being 11 to 12 cm in length and 13 to 14 g in weight. This hybrid is very popular in Gujarat.
JOH 05-9: Plants medium-tall (120-130 cm) and short internodal length. First flowering appears 40 to 41 days after sowing. Each plant has 19 to 20 fruit; fruits being 11 to 12 cm in length and 14-15 g in weight.
Kashi Bhairav: Plants medium tall with 2-3 branches; fruits dark green with 10 to 12 cm length at the marketable stage; yield 200 to 220 q/ha. This is resistant to yellow vein mosaic virus (YVMV) and okra leaf curl virus (OLCV) under field conditions.
Shitla Jyoti: Plants are medium tall, height 110 to 150 cm, flowering starts on 30 to 40 days after sowing at 4 to 5 nodes. Fruit is green, 12 cm to 14 cm long at the marketable stage, yielding 180-200 q/ha. Suitable for warm humid climate with relatively long day length.
TN Hybrid 8: Plants branched type, having sparse pigmentation except on fruits, green foliage. Green, 5-ridged, medium-long fruits. It is also a high yielder even under north Indian conditions. Resistant to yellow vein mosaic virus.
Cultivation Practices of Okra
Sowing
Sowing time depends upon the optimum temperature required for seed germination, growth, flowering, and fruiting. Spring/summer crop is sown between February and March while the rainy season crop can be grown in June and July throughout India. In southern India, it could be grown year-round. In north Indian hills, it is sown between April and June while in eastern and western India, summer crop sowing is done between January and February. In West Bengal, sowing continues from February to June.
Seed rates depend on sowing time and spacing. During summer the vegetative growth is relatively less hence row x row distance is kept 45 cm apart and plants are spaced about 20 cm apart. It requires 16 to 18 kg seeds/ha. Higher seed rate and lower spacing could also be opted for summer crops to lower the field temperature and keep fruiting going on under frequent light irrigation. Comparatively wide spacing (60 cm x 30 cm) is recommended for the rainy season which requires 8 to 10 kg seed/ha.
Chemical seed treatment with Carbendazim and Mancozeb @ 3g/kg seed protects seed from soil-borne diseases. Seed treatment with imidachlorpid 70 [email protected] 2.5 g/kg of seed protects the crop from whiteflies up to 25 to 30 days of sowing. Soil treatment with Furadon @ 2 kg ai/ha (20 kg to 22 kg product) helps protect plants from root-knot nematodes and other pests during the initial 4 to 5 weeks. Soaking seeds for 24 hr in water before sowing will enhance germination.
If soil is heavy, sowing should be done on ridges. It helps in supplying water to the plants uniformly, saving water in dry periods, reducing weed problems, and draining out the excess water in the rainy season. In saline soils, sowing of seeds on the sides of ridges improves germination and growth of seedlings since regular irrigation in channels lowers down the concentration of salts at the base of ridges owing to the accumulation of salts on the top of the ridge during a process of evaporation. In flatbeds, seeds are sown in furrows. This method is useful in areas where the soil is light-textured, well-drained, normal in reaction, not predisposed to water stagnation, and has sufficient irrigation facilities. For raising commercial crops, a seed drill can also be used for sowing.
Nutrition
Okra is a heavy feeder crop. It is advantageous to add 15 to 20 tonne/ha well rotten farmyard manure (FYM) before field preparation. Besides, for average fertile soil, 100 to 120 kg nitrogen (N), 80 kg phosphorus (P₂O₂), and 80 kg potash (K₂O) are required. Full phosphorus, potash, and 1/3rd nitrogen are mixed and applied as basal dose. The rest of the nitrogen is applied in two splits, 30 and 45 days after sowing. Excess fertilization can reduce yield by enhancing vegetative growth. Phosphorus and potash should be placed at 10 or 15 cm depth below the seed in two bands on either side of the seed furrow. Adopting an integrated approach using oilseed cakes (groundnut and neem both at 5% w/w) and a fungal bioagent Trichoderma viride at 5 × 10 € alone or in combination improves plant growth.
Irrigation
There should be sufficient moisture in the soil at the seed sowing. First irrigation should be given after seed germination. Subsequent irrigation may be given at an interval of 4 to 5 days during summer and as per need during the rainy season. Moisture stress during flowering and fruit/seed set causes around 70% crop losses. The nutrient uptake is also at peak during fruit set and development stages. Water stress in the field during this period not only causes yield reductions but also affects the nutritional status of the fruits. Drip irrigation saves around 85% water requirement though it is not yet commercial in okra. Furrow system is better than flood system.
Aftercare
Since okra is grown almost during two seasons all over the country during the warm period of the year, quick-growing weeds can be a serious consideration. If weed spectrum in the early stages of crop growth is high enough, the yield loss ranges from 49.39% to 91%. Pre-emergence application of Pendimethalin 1.0 kg/ha or Alachlor 1.5 kg/ha or Fluchloralin 1.25 kg/ha along with one hand weeding 40-45 days after sowing keep crop weed free and is economical for okra production. Thin out the closely germinated plants at one true leaf stage. In okra, 3-4 hoeings followed by a light earthing proved to be beneficial to keep the weeds down. The first hoeing should be done two weeks after the emergence of seedlings and subsequent hoeings at fortnightly intervals are needed to keep crop weed free up to critical periods. After sufficient vegetative growth, weeds get suppressed by the smothering effects of the crop.
Diseases and pests in Okra
Insects pests
Some of the important insects pests are shoot and fruit borer, jassid, aphid, whiteflies and mites etc.
Okra shoot and fruit borer: The fore wings of Earias vittella are pale white, with the broad wedge-shaped horizontal green band in the middle, while in Earias. insulana are uniformly green. Full-grown larvae are stout, brownish with milky white markings. Larvae bore into the tender shoots tunneling downwards and the affected shoots wither and growing points are killed. The entrance hole is plugged with excreta. The caterpillars bore inside the developing buds, flowers, fruits and feed on inner tissues. Damaged buds and flowers fall while affected fruits are distorted.
Fruit borer: Earlier, it was a minor pest of okra, known as Helicoverpa armigera. However, now it has become a major pest. Adult moths are medium-size, pale brown, olive green to brown wings with dark brown circular spots in the center. The young larvae feed on tender foliage, while advanced stages attack the fruits, bore circular holes inside the fruit. Larvae move from one fruit to another and may destroy many fruits. External symptoms appear in the form of a bored hole. (i) Deep summer ploughing to expose the larvae and pupae to sunlight and predation by birds. (ii) June’s first week of sowing is the most ideal to avoid the damage of shoot and fruit borer in the rainy season. (iii) Regular monitoring by light/pheromone traps (10 traps/acre) for early pest detection. (iv) Field release of biological control agents (Trichogramma brasiliense/T. chilonis @50, 000/ha against Helicoverpa armigera and Earias spp.).
Jassids: The adults (Amrasca biguttula biguttula) are wedge-shaped (2 mm) pale green with a black spot on the posterior half of each of the fore wings. The female inserts about 15 yellow eggs into leaf veins on the underside. Nymphs and adults suck sap usually form the under surface of the leaves and inject toxins causing curling of leaf edges and leaves turn red or brown called as ‘Hopper Burn’. The leaves dry up and shed. On transformations into winged adults, they feed constantly on the plant juice.
Whiteflies: The insect Bemisia tabaci breeds throughout the year and the female lay stalked yellow spindle-shaped eggs singly on the lower surface of the leaf. Nymphs and adults suck the sap usually from the undersurface of leaves and excrete honeydew. Leaves appear sick and get coated with sooty mold. The whitefly serves as the vector for the spread of yellow vein mosaic disease causing damage to okra crop. Many weed plants harbour whiteflies, removal of weed hosts found to reduce both the incidence of whiteflies and associated viral diseases. Conserve natural enemies, parasitic wasps, and predatory insects including ladybird beetles, damsel bugs, lacewings, and hoverfly larvae are important in the natural control of pests.
Red spider mites: It is a minor and irregular non-insect pest of the crop. The nymphs and adults are red. Its infestation is severe in dry and warm atmospheres. The nymphs and adults suck the cell sap form under the surface of the leaf and ultimately cause defoliation. The dried leaf drops away in case of severe infestation. Colonies of red mites are found feeding on the ventral surface of leaves under the protective cover of fine silken webs, resulting in yellow spots on the dorsal surface of leaves.
The management of red spider mites is possible by the destruction of infested plant parts during the initial stage of the attack.
Root-knot nematodes: Okra is highly susceptible to root-knot nematodes, Meloidogyne species. The above-ground symptoms are similar to those described for root rot and wilt diseases. The only difference is the appearance of root galls/knots of different sizes, instead of root rotting. The infected roots also become enlarged and distorted. The root-knot nematode has a wide host range.. Weed management, crop rotation and intercropping or mix cropping or cover cropping with non-host is recommended.
The management of root-knot nematode is possible by use of tolerant/resistant varieties; rotating okra with onions, baby corn, maize, millet, sorghum, sesame or Sudan grass and monocots for at least two to three years; maintaining high levels of organic matter in the soil; mix crop with marigold (Tagetes spp.) or Indian mustard; removing crop debris, and incorporation of bio control agents i.e. Trichoderma, Paecilomyces and plant growth promoting rhizobacteria (PGPR).
Diseases
Yellow vein mosaic disease: This is the most important and devasting disease of okra the in Indian sub-continent caused by yellow vein mosaic virus. First visible symptoms appear in the form of vein clearing, followed by a homogenous interwoven yellow network enclosing islands of green tissues within. In severe cases, younger leaves are completely yellow except for a few small scattered green patches. Most of the affected plants show thickening of the veins of the lower sides, and hardly one or two fruits often deformed small, pale in color, and tough in texture are produced on infected plants. The virus is neither sap nor seed transmissible. In nature, the disease is transmitted by the whitefly vector (Bemisia tabaci). The losses range from 50 to 94% depending upon the stages of crop growth at which infection occurs.
To manage the yellow vein mosaic disease- do rouging of diseased plants as soon as they are noticed in the field; and uproot the host plant in the surrounding of the crop.
Okra enation leaf curl virus:Twisting of the main stem and lateral branches along with enations leaves become thick and leathery. In severe cases, newly emerging leaves also produce conspicuous enations, thickening and curling. Mild and bold enations are prominent on the under surface of the leaves. The infected plants either do not bear fruits or produced few small and deformed fruits. Okra enation leaf curl virus OELCV is transmitted by white fly (Bemisia tabaci Gen).
All the control measures mention for Yellow Vein Mosaic Virus are applicable to OELCV.
Cercospora blight: The disease is caused by Cercospora abelmoschi. The fungus causes no definite leaf spot but grow as sooty to dark olivaceous ectoparasite covering entire leaf lamina. Disease initiated as small isolated fungal growth on the lower side of the leaf but very soon it spreads on both sides without any definite area. Pathogen reduces severely the photosynthesis area. Infected leaves fall down very quickly after drooping rolling, wilt, and abscise and making fungicide coverage difficult for management. It causes severe loss in seed production crops as well as the late sown crop grown for green fruits. Sometimes light brown-color lesions are observed after washing out spores from leaves due to rainfall. Okra sowing should be completed in the first week of July and collect the defo ted leaves and bur in the field itself to reduce the inoculums at the source.
Powdery mildew: The infection occurs on all plant parts, i.e., leaves, stems, and fruits. The pathogen (Erysiphe cichoracearum) produces grayish powdery growth on both the upper and lower surface of the leaves with a white coating of mycelium. Infected leaves turn yellow, curl, dry up and are shed. It is manageable with azoxystrobin or stylet oil dry weather conditions favor disease development. The early infection has more effect on the yield and plant growth than late infection.
Wilt: The crop is prone to the attack of the pathogen, (Fusarium oxysporum f. sp vasinfectum at all stages of plant growth. Affected plant shows yellowing and stunting followed by wilting and death. Dark streaks develop inside the infected stem. Crop rotation and destruction of plant material are helpful in minimizing infection.
Damping off: As previously stated, okra growers in India have adopted a high seeding rate. Due to this practice, damping off caused by (Pythium sp., Rhizoctonia sp.) is more common in this area, also at the times when growers are trying to push the season by planting in soil that is too cold. If the stand is affected to a great extent, the grower may choose to replant.
Harvesting and post-harvest management
Harvesting and yield: The fruits become ready for harvest between 45 and 60 days after sowing depending on variety and season. They are picked when still immature (5-7 cm long), before the differentiation of fibers, and before the seeds are fully developed. Generally, fruits are ready for picking at marketable stage in about 5-6 days after anthesis. Frequent pickings are necessary so that fruits do not grow too long making it unfit for marketing. For export purpose dark green, 6 to 8 cm long pods should be harvested. In USA, okra that is 7.5 cm long or smaller is marketed as extra fancy, more than 7.5 cm is sold as fancy. In general, harvesting every alternate day is advisable. Cotton cloth hand gloves should be used to protect fingers from uneasiness in harvesting due to presence of trichomes on all plant parts. Harvesting in the morning when hairs on fruits are soft is convenient to freight for the market. For distant markets harvesting in the late evening and transporting the produce during the cool of nights is practiced. An average yield of 80 q/ ha during spring-summer and 125 q/ha during the rainy season is optimum. However, yield up to 200 q/ha can be achieved with good management practices.
After harvest, the fruits are graded. For the processing industry and fresh fruit export 6 to 8 cm long fruits are sorted out. Longer fruits are suitable for the fresh market. Grading is beneficial in securing premium prices. For local markets, fruits are cooled (preferably) and filled in jute bags or baskets, covered or stitched. One should try to moist the fruits continuously till it is disposed of. This helps in cooling as well as in turgidity of fruits which tightens the pack and saves product from bruises, blemishes, and blackening. In air-tight containers the fruits may turn pale during transit owing to heat generated by the fruits. For export, suitable size paper cartons are preferred packages (5 to 8 kg size) wherein pre-cooled fruits are packed and transported preferably in refrigerated vans.
The storage life of okra pods is 2 to 3 days under ambient conditions. It is extended up to 7 to 8 days at room temperatures by pre-packing in unventilated polyethylene bags (100 gauge) and extended up to 16 to 18 days by storing the pre-packaged pods at low temperature (50-52° F and 85-90% RH).
