Unit –6
Cultivation Practices of Citrus
1.Mandarin (Citrus reticulata)
IntroductionCitrus is the collective generic term which comprises a number of species and varieties
of fruits, known to world over for their characteristics flavour and attractive range of colours. The attractive evergreen foliage and flowers as well as extraordinary fragrance added aesthetic value of citrus trees. Besides it, Mandarin is highly appreciated for their excellent quality fruit. Balanced ratios and specific blends of acidity and sweetness enriched with vitamins and other nutritive values constitute the citrus juice an excellent food source.
Origin and distribution
Mandarin oranges are native to the tropical and sub-tropical regions of Asia such as
southern Asia and the Philippines. It is most abundantly grown in Japan, southern
China, India, and the East Indies, and is esteemed for home consumption in Australia.
The commercial cultivation of mandarin oranges in the United States has developed mostly in Alabama, Florida and Mississippi and, to a lesser extent, in Texas, Georgia And California. Citrus, particularly the mandarin is the most important commercial fruit crop in the mid hills of Nepal. The area under mandarin is 65.16 per cent of the citrus fruits and 26.3 per cent of the total area covered by fruits in the country.
Variety
1. Pokhara beauty
2. Kamala
3. Coorg
4. Nagpur
5. Sutsuma
6. Khoku Local
2.Sweet Orange
(Citrus sinensis)Introduction
Sweet orange is tight skinned with solid control core pulp juicy and sour sweet. Seeds
are with whitish cotyledons. This is of great importance for its excellent quality and
its rootstock value is limited to some extent.
Origin and distribution
The orange is unknown in the wild state; is assumed to have originated in Southeast
Asia, Northeast India, and Southeast China. Sweet orange is commonly known as
Junar in Nepali, is successfully grown in 47 out of 75 districts of Nepal
Variety
1. Mausambi
2. Satgudi
3. Hamlin
4. Pineapple
5. Valencia
6. Novel orange
7. Jaffa
8. Malta blood red
3.LIME
(Citrus aurantifolia)Introduction
Limes are oval or round in shape having a diameter of one to two inches with green
flesh and skin. They can be either sour or sweet depending on the variety. Sour limes
contain citric acid giving them an acidic and tart taste, while sweet limes lack citric
acid and are sweeter in flavor.
Origin and distribution
Lime is believed to have originated in northern India and adjoining parts of Myanmar,or in northern Malaysia. The lime is now cultivated throughout the tropics and in warm subtropical areas. Acid lime is cultivated in terai, mid hill and high hill districts of Nepal.
Acid lime group
1. Citron (Citrus medica): monoembryonic seed
2. Acid lime (Citrus aurantifolia): Sour lime, Mexican lime, Key lime, West Indian
lime) or Kagzi lime
3. Tahiti (Persian) lime (Citrus latifolia)
4. Rangapur lime (Citrus limonia): Mainly used for root stock. It is considered to
be hybrid between mandarin and lemon like fruit.
5. Sweet lime (C. limettioides)
6. Rough lemon (C. Jambhiri): It is indigenously found in Nepal. It is mainly used for making concentrated Nibu juice. An important root stock.
7. Grapefruit (C. paradisi): Closely related to pomelo. As the fruits are borne in
cluster (upto 12) like grapes.
Varieties:
i. Tehrathum local
ii. Rampur-01
iii. Rampur-10
iv. Maxican
v. Banaras local
4. LEMON
(Citrus limon)
Introduction
Lemons are oval in shape and feature a yellow, texturized outer peel. Like other Citrus fruits, their inner flesh is encased in eight to ten segments.
Origin and distribution
The lemon, Citrus limon (L.) is a species of small evergreen tree in the flowering plant
family Rutaceae, native to South Asia, primarily North eastern India. Lime and lemon are extensively distributed throughout the mid hills stretching from Illam district in the east to Darchula district in the far west of the country.
Variety
1. Sunkagati 1
2. Sunkagati 2
3. Nepali amilo
4. Assam amilo
5. Suraka round
6. Eureka
7. Libson lemon
8. Lucknow seedless
5.PUMMELO
(Citrus maxima)
Introduction
Pummelo belongs to citrus race and are closely related to Grape fruit. It is a very large,round to pear-shaped, yellowish orange fruit with very thick skin.
The fruit can weight upto 10 kg. The texture is fleshy and has more membrane than
many other types of citrus fruit.
Origin and distribution
Pomelo is native plant of Malayu Island and East of India. It is wide spread in China,
Japan, Philipines, Indonesia, USA and Thailand.
Variety
1. Chandler
2. Webber
3. Ichang
4. Red Shaddock
5. Reinking
Composition and uses of citrus
Citrus are rich source of vitamin C and minerals. They are rich in citric acid. Ripe
fruits are consumed as fresh and also used to prepare jam, jelly, candy etc.
Climate and soil of citrus
Citrus are sub-tropical fruits. They can be cultivated up to an altitude of 700-1500
masl. The ideal temperature is 15-250
C. They require 1200-1500mm annual rainfall.
They can be cultivated in loam and sandy loam. The pH should be 5-6.5.
Propagation and rootstocks in citrus
BuddingThe most common methods of budding citrus are shield or T-budding. Budding should preferably be done at 20 to 30 cm height on the stock.
Rootstocks
A good citrus rootstock should have high degree of polyembryony, compatibility with
the scion, adaptability to various soils, tolerance to cold, drought and wind, tolerance to viruses, fungal diseases and nematodes. Some of used rootstocks are: Sour Orange,Sweet Orange, Rough Lemon, Trifoliate Orange etc.
Planting of citrus
In citrus, square and rectangular system of planting are generally practiced. The
planting density usually varies from 200 to 400 plants per hectare but density planting
is also followed using modified agro-techniques. In square system, spacing of 5 m x 5m (400 plants/ha) and in rectangular system the spacing of 3 m x 5 m (667 plants/ha)can be maintained. In a well prepared land, sapling should be planted in a pit size of 1m x 1m x 1m.
Irrigation in citrus
Irrigation is required during flowering and fruiting stage. Sudden heavy irrigation
during flowering and fruiting may cause flower and fruit drop. It requires irrigation at 7-10 days interval in summer and 15-20 days interval in winter.
Manure and fertilizer in citrus
50 kg FYM/plant/yr.
870g Nitrogen/plant/yr.
540g Phosphorus/plant/yr.
830g potassium/plant/yr.
Training and pruning in citrus
An ideal citrus tree should be low headed with a roof like crown. This can be achieved
by pruning young trees. Modified center leader is best suited for citrus trees. Trees are trained to single stem with 4-6 well spaced branches for making the basic
framework. The lowermost branches should be allowed not to grow below the height
of 75 cm from the soil surface. The bearing trees require little or no pruning. Pruning
of bearing trees though differs with variety but chiefly consists of removal of dead,
diseased, criss-cross and weak branches. Removal of water sprouts and sucker of rootstock is also highly essential. Pruning of non-bearing trees can be done at any time
of the year. But for bearing trees the best time is after harvesting, during late winter or early spring when these are in somewhat dormant stage.
Intercropping in citrus
Interspaces in a young orchard can be economically utilized by growing short duration crops till the citrus plants come into bearing. Selection of intercrop is essential to
improve the soil fertility. The intercrop should be of short duration, shallow rooted,
non-exhaustive and preferably of leguminous type.
Intercultural operations in citrus
Major weeds can be controlled by hand pulling, hoeing, burning and tillage. However, frequent tillage may destroy the surface structure of soil, thus lowering the water holding capacity and permeability of soil. So, better way to eradicate weeds is use of weedicides. Pre emergence application of Diuron (5kg /ha) or Terbacil (4.5 kg/ha) or
post emergence application of Atrazine (5-6 kg/ha) controls weeds significantly. Further, Bromocil (6kg/ ha) is most effective in controlling both monocot and dicot weeds. Glyphosate (5 liters/ ha) is most effective in controlling perennial grasses. Simazine (5 kg/ha) is also highly effective.
Pollination in citrus
Pollination is greatly aided by insects, in particular honey bees. Citrus pollen is heavy
and sticky and is not blown by wind.
Flowering and fruit set in citrus
Flower takes place in the month of Jestha-Ashar. The fruitlets develop in the month of
Bhadra-Ashoj. Hot winds and excessive heat during flowering and fruit set are highly
detrimental for fruit bearing and cause fruit drop and sunburn of the fruit. Low
humidity favors colour development, whereas plants not having adequate sunlight
produce low yields of poor quality fruits.
Bearing habits in citrus
Some citrus groves tend to have a bearing habit with alternating high and low yields.
A heavy crop of fruit tends to deplete carbohydrates and results in a small crop and increased vegetative growth in the following year. Pruning after a light crop and before an expected heavy crop should help reduce alternate bearing. The orientation of branches in space has a marked effect on growth and fruiting.
Favouring horizontal branches over upright ones should result in better growth control and more fruit production.
Insect pest of citrus
1. Aphid (Toxoptera citricida, Myzus percicae, Aphis gossipi)
The adult and nymph suck the sap from tender parts of the plant, leaves,
flowers and fruits.
It causes the stunted growth of plant and reduction in yield.
Control:
Adopt clean cultivation
Spray Dimethoate 30% EC @ 1-2 ml/l or Imidachloprid 17.8% SC 0.3ml per litre of water.
Use lady bird beetle to control the population of aphid.
2. Scale insect (Aonidiella auriantii, A. citrina)
They suck the sap from tender parts of the plant, leaves, flower and fruit.
The affected part gets damage which result premature fruit drop and
defoliation.
Control:
Adopt clean cultivation.
Spray the Dimethoate 30%EC @ 1-2ml/l of water.
3. Citrus Psylla (Diaphorina citri)
They suck the sap from the tender parts of the plant, leaves, flowers and
fruits.
They create honey dew on the leaves in which shooty mould is developed.
Control:
Establish nursery about 1300masl.
Destroy the secondary host i.e. Kamini flower of this insect.
Spray Dimethoate 30%EC @ 2-3ml/l of water.
4. Leaf Miner (Phyllocnistis citrella)
Very small larva bore in the tissue of the leaves and make zig-zag tunnel.
Feed on the chlorophyll internally due to which the tunnel looks silver colour.
Control:
Spray tobacco based pesticide.
e.g. Soak 250 tobacco in 400 liter of water and mix with 30g surf. Keep
it whole night and filter it. Now add one part of this solution in a पत्त of water and spray at 10 days interval.
Apply 0.06% solution of Thiamethoxam 25 WG
5. Stem Borer (Inderbela spp)
The larva feed on the stem and trunk of the plant.
They make tunnel internally.
Leaves fall on severe condition.
Control:
Adopt clean cultivation.
Use wire to kill the insects inside the tunnel.
Use malathion soaked cotton to plug the tunnels.
6. Lemon butterfly (Papilio demoleus)
Female lays eggs on the fruit.
After hatching larva feed on the pulp of the fruit causing rooting and dropping
of fruits.
Control:
Collect and destroy the affected and falling fruits.
Destroy the larva and eggs of the insect.
Spray Cypermethrin 10% EC @ 2ml/l of water.
Disease of citrus
1. Die-Back
C/O: Fungus
S.N: Colletotrichum gloeosporioides
Symptoms:
The leaves become yellow in initial stage and turn into dark colour and start
to fall with beginning of summer.
Die-back of twig starts leading to dry and finally the plant dies.
Control:
Remove dead twigs or affected part from the plant.
Spray Carbendazim @ 1g + 2 g kaucho/l of water.
Bordeaux mixture 2:2:250 in April, July-August and September spray.
2. Phytophthora rot (Root rot, Crown rot, gummosis)
C/O: Fungus
S.N: Phytophthora parasitica
P. citrophthora
Symptoms:
Dark discolouration of bark is developed, water soaked spots developed
which cause stem rot, rootlet rot and finally defoliation.
In advance stage bark cracking and oozing of gums takes place.
Control:
Avoid water logging condition at the base of the plant.
Scrap the affected part.
3. Citrus Canker
C/O: Bacteria
S.N: Xanthomonas citri
Symptoms:
It is a serious disease in citrus fruits.
It affects the quality of fruit and reduces market value.
Water soaked with round spots are seen on the leaves and stems as well as in
fruits.
The spots increases slowly and turn into brownish on the leaves, stems and
fruits.
Control:
Remove and destroy the infected part of the plant.
Spray Bordeaux mixture @ 1% on cut portion.
Streptocyclin @ 1g/l of water initially.
4. Greening
C/O: Bacteria
S.N.: Libribacter asiaticus
Symptoms:
Initially vein and veinlet turns yellow and then interveinal cholorosis is observed.
Leaves become leathery, small, pair in mass and bend downward of seasonal
flowering.
Die-back symptom is another major symptom of this disease.
Division of cloves are not in equal proportion and seeds are not viable.
It is transmitted by citrus phyla.
Control:
The infected parts are destroyed.
Spray Diemethoade @ 2-3ml/l of water to control the vector citrus
phyla.
Apply Bordo pest in cut portion.
Spry Streptocylin @1g/l of water after pruning.
5. Powdery Mildew
C/O: Fungus
S.N: Oidium tingtitatum
Symptoms:
White powdery mass appear on the twigs and a
Control:
Destroy the affected plant part.
Spray Bavistin @ 1-2g/l of water at 20 days interval but in severe
infection spray 8-10 days interval.
6. Tristeza Virus
Symptoms:
It is a serious disease of citrus family.
It cannot be controlled easily.
Initial symptoms are seen like development of small leaf like green in colour, small fruit with sour test.
At later stage, the plant wilts and dies.
Control:
Destroy infected plant part.
Spray Dimethoate 30% EC @ 2 ml/l of water to control sucking pest.
Physiological disorder in citrus
1. Fruit drop
In spite of very high initial flowering and fruiting, the ultimate yield is often low
primarily owing to heavy fruit drop. However, all fruits that fail to mature do not drop at one time but at different times. Fluctuating temperature, low atmospheric humidity, imbalance of soil moisture, lack of proper nutrition, hormonal imbalance, incidence of iinsect pests and diseases are some factors causing fruit drop. Accordingly,
maintenance of appropriate soil moisture level during fruit development can decrease
fruit drop problem. Application of growth regulators 2, 4-D (10 ppm), NAA (5ppm)
check fruit drop quite effectively.
2. Granulation
It is a physiological disorder of juice sacs of citrus including mandarins wherein they
become comparatively hard and become somewhat enlarged. Young, vigorous trees
are more likely to develop granulated fruits than older ones. Similarly, large fruits
have more granulation than small ones. Spraying of lime reduces the extent of
granulation. The applications of 2, 4-D (12ppm), zinc and copper reduces the
incidences of granulation considerably.
3. Decline
After fruitful production from about 15 years, citrus orchards start bearing little crop and become uneconomical. They show symptoms of ill health and decline. The
affected trees do not die completely but remain in state of decadence and
unproductiveness for a number of years. Initially, only a few limbs of the plants are
involved but later whole tree is affected. Plants show sparse foliage, stunted growth,
and sickly appearance and in leaves, mid-rib, lateral veins and intervenal area show
diffused yellow color leading to ultimate shedding of leaves. As a result of dieback,
twigs become short and bear only a few narrow leaves at their basal ends. Such plant are also characterized through excessive flowering and very poor fruit
set. Unfavourable soil conditions (presence of hard pan, high pH, poor drainage and
high salts), malnutrition, poor orchard management, indiscriminate use of fertilizers, intercropping, incidence of insect pests and diseases are major factors contributing to it. Good cultural practices, improvement in soil fertility and drainage, control of insect pests, nematodes and diseases may be useful to minimize its incidence. Use of resistant and compatible rootstocks and certified bud wood for propagation are strongly recommended for a healthy and productive mandarin orchard.
Stage of maturity
Picking of fruits at proper stage of maturity is paramount importance. Harvesting atright time not only maximizes profits but also helps build up the demand for quality
fruits. Unlike climate fruits, mandarins do not improve in taste after
harvesting. Therefore, fruits should be harvested when they attain full size, develop
attractive color with optimum sugar: acid blend
Harvesting methods
Harvesting should be done carefully without causing damage to the fruits. Slight
bruising or injury to the rind leads to quick decay of fruits. Harvesting can be done by
shaking the branches with a pole and also by hand using a ladder. Mechanical
harvesting systems consisting of abscission chemical and trunk shakers, pick up
machines and automatic robotic fruit picking are also available.
Yield
Generally, Citurs tree yields about 10-12 tones/ha.
Grading and packaging
Generally, citrus are graded according to their size and appearance. Fruits are usually
packed in wooden boxes for distant markets, while for local marketing baskets of split
bamboo and mulberry are used. Chopped straw and dry grasses are mostly used for
padding. The fruits should be cleaned and polished lightly with a piece of cloth, before
wrapping them in tissue paper or newspaper. Use of corrugated fibre board cartons in place of wooden boxes is highly beneficial.
Transport and storage
Citrus are generally transported by rail or road as ordinary cargos without refrigeration which often leads to heavy losses due to decay and fungal infection. Use of shrink films for moisture loss control can be useful. Storage life of mandarins is influenced by many pre and post harvest factors. Green or fully ripe citrus fruit can be stored successfully at 8-10`o
C with 85-90% relative humidity without impairing fruit quality. Similarly, Kinnow fruits can be stored at room temperature up to 3-4 weeks in perforated 100 gauge polythene bags having 0.5% ventilation area.
The end