Transcript L-11_Rhubarb.ppsx

Lecture 11
RHUBARB
Botanical Description
Botanical Name :
Rhubarb rhaponticum
Family
:
Polygonaceace
Ch. Number
:
2n=22
Origin
:
Southern Siberia and China
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.
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.
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.
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
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.
Soil
• It should be well drained.
• Rhubarb prefers deep, fertile loams and
does best in slightly to moderately acid soil.
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.
 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.
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.
 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.
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.
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).
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.
 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.
 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.
 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.
MANURES AND FERTILIZER:
 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.
 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.
 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.
• 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).
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.
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.
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.
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.
 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.
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.
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.
Seed Production
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.
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 20-30 days of the
sowing in order to determine isolation, volunteer
plants, out crosses, off types and other relevant
factors.
• 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.
II. Field Standards:
A. General Requirement:
Isolation:
Contaminants
Minimum distance(meters)
Mother root production
stage
Seed production stage
FS
CS
FS
CS
Fields of the other
varieties of the same
species
5
5
1600
1000
Fields with same variety
not confirming to varietals
purity requirements
5
5
1600
1000
B. Specific requirement:
Factors
Maximum permitted (per cent)
FS
CS
Off type
0.10
0.20
Plant affected by
seed born diseases
0.10
0.50
III.SEED STANDARDS
Factors
FS
CS
Pure seed (min.)
98%
98%
Inert matter (max)
2%
2%
Other crop seeds (max)
5/kg
10/kg
Weed seeds (max)
10/kg
20/kg
Germination (min)
60%
60%
Moisture (max)
7-9%
7-9%
For vapour proof
container (max)
5%
5%
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.
• 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
Grammaxone or Paraquat.
or
with
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.
 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.
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.
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.
• 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.
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.
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.
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.
• 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.
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.
Control:
• Remove and destroy leaves following the
first heavy frost.
• During harvest, remove stems with spotted
leaves first. Apply fungicide used for
Botrytis control.
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.
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.
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.
• They may be introduced in infected
planting stock.
Control:
• Obtain and plant healthy nursery stock.
• Avoid planting virus free crowns near
virus contaminated crowns
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
• Field yields can vary depending on the age and
vigor of the stand.
• Yields can range between 15.000 and 40,000 kg per
ha (13.500 and 36.000 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
 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 5- 10
years.
 Seed crop start to harvesting from three years age
onwards.
 Seed yield varies between 250-400 kg/ha.
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.
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.
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