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Lecture 11 RHUBARB.

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1 Lecture 11 RHUBARB

2 Botanical Description
Botanical Name : Rhubarb rhaponticum Family : Polygonaceace Ch. Number : 2n=22 Origin : Southern Siberia and China


4 AREA AND PRODUCTION Rhubarb is a native of the cooler areas of Asia, probably Siberia but it is grown in Europe and England and used as a tilling for tarts and pie. A Maine grower who obtained seeds or rootstalks from Europe Jrew rhubarb in the United States as early as 1800. It is commercially cultivated in the Massachusetts.

5 Rhubarb can be grown as an outdoor plant and as a forcing plant.
Varieties: Rhubarb can be grown as an outdoor plant and as a forcing plant. Cultivars of rhubarb may also be chosen according to the cooler to their petioles.

6 The cultivar MacDonald has large red stalks.
For outdoor production: The cultivar MacDonald has large red stalks. It is vigorous and upright growing. Valentine is another red stalked cultivar that is popular for growing in home gardens.

7 For forcing : Timperley, Early Victoria, Crimson Red and Sutton are
used. Green-stalked cultivar : Victoria, is a heavy producer and excellent for commercial purposes. Pink- stalked cultivar : Sutton

8 Land Requirement Before planting this polygonaceae crop, consider the following important factors: No polygoneous crop (Sorrel) or related weed (dock plants) has been present in the Held for at least 2 years,4 years preferable. Polygoneus crop like Buckwheat. Also, polygoneous crops waste should not have been dumped on these fields.

9 Soil It should be well drained.
Rhubarb prefers deep, fertile loams and does best in slightly to moderately acid soil.

10 CLIMATE Rhubarb is a cool-season, herbaceous, perennial crop . It grows best when mean summer temperatures are below 75° F or when winter mean temperatures are below 40° F. Grown in the northern tier of the United States in a region extending from Maine south to Illinois and west to Washington.

11 The plant requires temperatures below 50° F to break dormancy.
Rhubarb is not easily grown in the southern United States because high temperatures disrupt growth. Cultivars that exhibit good pink or red petiole colour during the cool season usually becomes very green when temperatures remain above 85° F. The vegetative parts of the plant are killed at 26° or 27° F.

12 PLANTING Rhubarb is usually propagated by dividing the crowns formed during the previous season. Crowns are divided in late fall or early spring. Plants must be divided and reset every 4 years to keep the bed in vigorous condition. Plants not divided may become large and stalks may become more numerous than desired. Seed stalks should be removed as they appear.

13 Typical spacing for commercial rhubarb planting is rows 4 ft apart with plants 4 ft apart in row.
Trenches are dug prior to planting, generally 6 inch deep. Crown pieces are placed 2 inches below the surface of the soil in the trench. Soil is pulled over the soil and firmed. Good drainage is essential for growing rhubarb.

14 Irrigation The rhubarb plant responds well to moisture, although reliable yields can be obtained with minimal watering. Irrigate prior to harvest to increase crop yield and delay irrigation after harvest until plant injuries have healed.

15 Mulching Straw may be applied in late fall or during the winter as a mulch to keep down weeds and ensure a cleaner harvest environment from soil. Straw mulch may also be used to surface burn a held to control diseases and insects (especially potato stem borer). 

16 The first growing season –
Culture and Care The first growing season – Plant only in fields that are as clean as possible from perennial weeds. Cultivation should be shallow and throughout the growing season. Some hand hoeing will be required: contact herbicides may be sprayed between the rows with the crop shielded. Flower stalks should be cut off as soon as they appear.

17 One or two side dressings of nitrogen may be necessary.
No crop should be harvested the first season. In the fall, well rotted manure and/or straw should be applied to the soil surface. Following years – Cultivate occasionally to keep weeds in check but be careful not to cultivate too deep or close to the crown and fleshy roots.

18 Rhubarb grown for seed production is planted in a field for 2 years in which the stalks and petioles are not harvested. After 2 years of growth the roots are ready to be dug for seed production. It should be exposed to the low temperature to break the dormancy.

19 The crown and roots used for seed production must be dug before the soil freezes, taken storage, and held where dehydration and water loss are at a minimum until it used for planting. When ready for planting, the crowns are packed together on 4-5 ft wide beds with soil and water added to initiate growth, and then placed in the dark.

Rhubarb grows best in soils with a pH in the range of 6 to 6.8. The crop has a high demand for calcium and magnesium. Rhubarb is a heavy feeder, therefore will do best on sandy loam to loam soil with a good organic matter level. To achieve early field production, plantings need to be made on light soils with a southerly exposure. The site should also be sheltered.

21 Rhubarb can remove upwards of 220 kg/ha of nitrogen from the soil.
The nitrogen should be replaced in 2-3 applications with the first application at bud break. The remaining applications should be made after harvest. Try to avoid putting nitrogen fertilizer to close to the roots as it can burn the small feeder roots.

22 All additions of lime and fertilizer or manures should be based on recommendations from a soil test.
When test results are not available the general requirements from Tables 1-4 of the soil and water management section of this guide may be followed. Phosporus is not very mobile so select a planting site that is high in phosphorus. If additional phosphorus is required it can broadcasted with nitrogen and potassium early in the spring and mixed into the soil with a light cultivation between the rows.

23 Rhubarb grows well in a highly fertile soil high in organic matter and well drained.
A green manure crop is desirable the year before planting. Also in the fall 45 tonnes of manure per hectare may be added. (An annual fall application of manure would be beneficial).

24 Lime Is applied to maintain the soil pH in the range 6.0 to 6.8 (rhubarb will tolerate soil acidity as low as 5.0 but yields and fertilizer efficiency will suffer). As with all crops the calcium level should be 3000 kg/ha to be in line with current soil testing methods.

25 Nitrogen Rhubarb has a high requirement for nitrogen. Apply only as necessary in the establishment year. Otherwise apply nitrogen at bud break along with the phosphorus and potash requirements. Apply one or two side dressing of nitrogen after harvest ( delay until good regrowth has began) or on crop to be used for forcing. Application of manure will supply part of the nitrogen requirement of this crop.

26 Is the most important in the establishment year.
Phosphorus Is the most important in the establishment year. Field selected for rhubarb should be high in phosphorus. Potash Is the only added if soil level are not adequate but is usually required if high yields are being taken and manure is not being used.

27 Magnesium & /or Sulfur May be needed on sandy soils low in organic matter. Foliar sprays of epsom salts or the use of gypsum and dolomitic limestone may be considered. Micronutrients Boron may be necessary for the health of buds and roots. It may be applied in the fertililzer , as soil drenches and / or foliar sprays.

28 Apply 1 to 2 kg per hectare per year of actual boron.
Be careful not to burn foliage or roots in the establishment year. Application method – Broadcast N, P & K in the spring and apply manure in the fall. Sidedress or broadcast nitrogen or apply it through an irrigation system. Cultivation between the rows will mix some of the broadcast fertilizer into the soil and control some weeds.

29 Use of Growth Regulators
Gibberellic acid is useful in rhubarb forcing to assist in breaking dormancy to permit early production. This may allow time to force two crops in the house. Gibberellic acid also tends to increase yields.

30   Roguing:  Timely and regular interval rouging for off type, diseased plants affected by crown rot. Viral diseases infected plants are important also, weed like dock plant removed at regular interval.

31 Seed Production

32 Method of Seed Production
There are three major methods used to produce seeds in Brussels sprout. seed to seed method root to seed method Out of these three methods, root to seed method is commercially used for production of seeds.

33 A. Mother Knots/Crowns production stage:
Seed Certification Standards:   I. Field Inspection: A. Mother Knots/Crowns production stage: Minimum two inspections arc required to produce quality seeds.   The first inspection is done after days of the sowing in order to determine isolation, volunteer plants, out crosses, off types and other relevant factors.

34 The second inspection is done after the mother roots have been lifted to verify the true characteristics of roots. B. Seed production stage: A minimum of one inspection is done during flowering to check isolation, off types and other relevant factors.

35 Minimum distance(meters)
II. Field Standards:  A. General Requirement: Isolation: Contaminants Minimum distance(meters) Mother root production stage Seed production stage FS CS Fields of the other varieties of the same species 5 1600 1000 Fields with same variety not confirming to varietals purity requirements

36 B. Specific requirement:
Factors Maximum permitted (per cent) FS CS Off type Plant affected by seed born diseases 0.10 0.20 0.50

37 III.SEED STANDARDS Factors FS CS Pure seed (min.) Inert matter (max)
Other crop seeds (max) Weed seeds (max) Germination (min) Moisture (max) For vapour proof container (max) 98% 2% 5/kg 10/kg 60% 7-9% 5% 20/kg

38 Weed Management Control weeds well before planting.
Start cultivation early in the spring. Cultivation should be shallow to avoid injury to roots and can continue as late in the season as possible without damaging the plants.  Contact herbicides are registered for use but the crop must be well shielded.

39 Various types of mulch may be used between the plants and in the rows (most commonly straw).
Grass weeds can be controlled with glyphosate or round-up or with Grammaxone or Paraquat.

40 Insect Management Potato stem borer Characteristics The potato stem borer is a caterpillar, which when fully grown is about 3.5 in length and pinkish-white in colour. The first stages of the insect attack only weeds, couch grass in particular. Later they move into plants with thicker stems, such as rhubarb.

41 They may move from stem to stem, boring into the centre of the stalk.
The adult moths lay their eggs on the stem of grasses in August. The eggs do not hatch until the following spring. Damage can be expected in June and early July. Serious infestation can lead to an unmarketable crop.

42 Control: This pest is not a problem when couch grass and other weeds are controlled in and around the rhubarb plantation. Weeds should be controlled to make the field less attractive for egg laying by the adult moth. Early spring burning of affected fields or field margins will effectively control this pest.

43 Tarnished plant bug Characteristics: Adult tarnished plant bugs are light brown to reddish brown in colour and about 5-6 mm in length. They occur throughout the season. They are very active and quick moving. They can damage rhubarb by feeding on young leaves.

44 They pierce the stalk with their mouthparts and cause wilting and distortion of the leaves.
Tarnished plant bugs are mainly a pest of new plantings. Control Keep plantings and adjacent areas weed free. Avoid planting adjacent to legumes.

45 Slugs Characteristics: Slugs may be a problem in plantings with heavy soils, poor drainage and in weedy situations. Slugs fed at night, by rasping the surface of stems, leaving unsightly scars, which reduce the sale ability of the stem.

46 Prevention: Provide good soil drainage. Keep weeds under control.
Remove leaves and trash from the field when harvesting. Do not use manure and/or mulches in areas of field prone to slug damage.

47 Other Insect Pests Black bean aphid (Aphis fahae) : caused problems on occasion. Large infestations may cause curling or wilting of leaves. There is also potential for the spread of virus by aphids.

48 Flea beetles - can cause damage to new plantings by their feeding activity on the leaves.
They are especially active during periods of hot dry weather.   Control: Provide good weed control. There are no products registered for either of these pests.

49 Diseases Management:   Leaf Spots and Ascochyta leaf spot These fungi cause circular, or angular spots, variable in size having beige centers surrounded by a red zone. When affected tissue dies, it may drop out. leaving large ragged holes in the foliage. Fungi overwinter in infected plant debris and in infected propagation stock.

50 Control: Remove and destroy leaves following the first heavy frost. During harvest, remove stems with spotted leaves first. Apply fungicide used for Botrytis control.

51   Botrytis Rot (fungus) May cause a leaf, stem and crown rot of forced rhubarb. Disease intensifies where there is poor air circulation and high humidity. Control: Practice strict sanitation. Apply recommended fungicide at first sign of disease and at 7 day intervals.

52 Root and Crown rots (fungi and bacteria)
Characteristics: Plants become unthrifty. Leaves may turn yellow to red and collapse. The Crowns, Sectioned, exhibit a brown-black lesions present.

53 Virus Characteristics: Several viruses are known to occur in rhubarb. Reports from British Columbia and the U.K. indicate that turnip mosaic , arabis mosaic. and cherry leaf roll virus are the most common. These viruses have wide host ranges and cause mottling and ring spotting of leaves.  

54 They may be introduced in infected planting stock.
  Control: Obtain and plant healthy nursery stock. Avoid planting virus free crowns near virus contaminated crowns

55 Red varieties tend to yield about half of the green varieties
Harvesting and Yield   The best time to harvest a seed crop is at stage when the highest yield of best quality seeds will be obtained. Seed crops are harvested when plant start drying in the field and seed are usually dried on the plant before harvesting. Plants are manually harvested cutting with ground level or whole plant pulls up and threshed to remove the seeds. Red varieties tend to yield about half of the green varieties

56 Field yields can vary depending on the age and vigor of the stand.
Yields can range between and 40,000 kg per ha ( and lbs/acre) in a single cutting harvest season. Harvest begins in late May or early June depending on location and can last for 8 to 10 weeks. Rhubarb is harvested by hand. The stalks are pulled rather than cut

57 The leaves are removed in the field and only the stalks are marketed.
Harvesting the year following planting is possible but has been found to reduce productivity in the long run. Second year harvests are preferred. A healthy stand should remain productive for years. Seed crop start to harvesting from three years age onwards. Seed yield varies between kg/ha.

58 Seed Package   Well dried Seeds are packed in the plastic bags, tin cans, cloth bags etc. packing or bagging consists of following operations. Filling of seed bags to an exact weight. Placing leaflets in the seed bags regarding improved cultivation practices. Attaching labels, certification tags on the seed bags and sewing of the bags.

59 Seed Storage Seed can be store at 0 2°C and a relative humidity of 95 to 100%. Under these conditions, seed can be stored 1-2 years. Good air circulation is also essential.

60 Thanks

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