CITRUS CULTIVATION IN NEPAL

Writer: Jiwan bdr karki

Adress: Duhan R.M-3 Darchula       

Study: Bsc ag 1st sem,valley krishi campus                 

                   

INTRODUCTION:

Citrus are believed to be native of tropical and sub-tropical region of  South East Asia. It belongs to the family Rutaceae.Citrus includes oranges, lemons, limes, pummeloand grape fruit etc. There is strong possibility that some of the citrus species originated from Nepal, particularly the lemon and lime. More than 62 districts of Nepal grows citrus, more than 42 istricts have commercial cultivation. Mandarin covers about 62% of the total production followed by Junar 22%, Lime 12%, lemon 3%, others 1%. Almost all the cultivated species, varieties and forms of citrus, fortunella and poincirus are diploid, the monoploid nummer of chromosome being 9. i.e. 2n=18.

USES:

Fruits are used as squash, juice, marmalade, fresh fruits, lemonade etc.

The rind of citrus fruit contains pectin and essential oils. The outer rind is called  flavedo and inner portion as albedo.

Usually used as fresh fruit

Orange marmalade, bottling and canning

Lemon and oranges are most important citrus oils used for flavoring purpose.

CLIMATE AND SOIL:

Citrus trees are evergreen, subtropical climates of the world although in tropical regions of the world. The best climatic condition suitable for Mandarin and sweet orange is 1000-1400 MASL with annual average temperature of 19°C.Lime can be cultivated successfully 500-1400 MASL and Lemon 500-1000 MASL. Citrus fruits grow best between a tempt. range of 13°C to 37°C.Soil tempt. around 25°C seems to be optimum for root growth.Increase in altitude, the fruit of mandarin and orange becomes smaller, more acidic with thick skin. While in relatively lower altitude; the fruit become sweeter with proper color development. Low humidity favor seed color and external appearance but high humidity favors thin skinned juicy fruits. Annual rainfall of 1250-1850 mm.

Citrus can grow well in a wide range of soils. For good performance, deep (2-3m). Well drained, free of excess salt (i.e less < 1000 ppm) with fair humus content is considered good. The soil having PH value 5.5- 6 is the best.

CULTIVARS (VARIETIES):

1)Mandarin( Citrus reticulata): Pokhara local, Dhankuta local, Decopon, Murcott, Okichu, Imamura wase, Nagpuri, Khasi, Kinnow etc.

2)Sweet orange(Citrus sinensis): Junar, Valencia, pineapple, Malta blood red, Rubi, Vanila, Washington Navel, Thompson, Yoshida Navel, Morita etc.

3)Lime(Citrus aurantifolia): Sun kagati, Kagzi lime, Persian lime, Mexican lime etc.

4)Lemon(Citrus limon): Eureka Round, Eureka oblong, Nepali oblong, Libson, pant-1 etc.

PROPAGATION:

Citrus tree are propagated both by seed and vegetative methods like grafting, budding and layering.

1)SEED:

Sandy loam soil is best for raising citrus nurseries.

The seeds should be shown soon after extraction within three days; otherwise it is likely to lose viability.

Sowing of seeds is done during spring (Feb - March)

The time taken for germination may vary from 2-3 weeks.

6 to 9 months or one year after sowing, the seedlings are transplanted in a nursery bed for hardening them.

The seedlings are transplanting into a nursery beds at the spacing of 45-60 * 20-30 cm. 

2)VEGETATIVE:

Budding is universally practiced in case of sweet orange, grape fruit, air layering and even cutting in lemon and sweet lime.

The seedlings becomes ready for budding an about a year.

Budding is generally done either in Spring or in August- September.

PLANTATION:

Wider spacing is recommended for vigorous growing citrus species like sweet orange, grape fruits, mandarin orange etc, while acid lime are set as closer spacing. Similarly, the citrus tree on dwarfing root stock like trifoliate, citrange are planted at wider distance.In general, 4-6m spacing is recommended. A pit of 1m3 size is suitable for planting.

#Mandarin: Normal spacing is 6m*6m

# Sweet orange: Normal spacing is 5m*5m

# Limes/lemons: Normal spacing is 6m*6m/5m*5m

PLANTING SEASON:- Monsoon and Spring

WEED CONTROL:-

Eradication of weed is essential at any time of year.

For Nepalease condition, cutting, burning, hand and mechanical weeding, raising intercrop and chemical control can be practiced.

The most commonly used herbicides in citrtus is MOnuron, Diuron, Simazine, Bromacil.

INTERCROPPING :

Should be shallow rooted, short duration, should have good canopy cover to protect soil from erosion, profit yielding

Early years of the orchard establishement

Crop like onion, chilli,potato, soyabean, cabbage, can be grown as safe intercroping.

IRRIGATION:

In the condition of the loss of moisture in soil we should apply irrigation to the plants.We can use ring basin method for irrigate the fruit plants.

TRAINING AND PRUNING:

The training is to give a desirable shape and strong framework and aids in securing good quality fruits over a long period of time. The training should start right from the time of scion-bud sprouts and should be complicated within 3 years of planting. Modified center leader is well suited for citrus trees. 

Pruning so as to maintain the framework and to secure higher yields of better quality each year of bearing tree is essential. Removal of water shoots, stock sprouts dead, dried and disease wood is necessary regularly. All the criss crossing branches in the centre of the tree should be removed. The best for pruning the bearing tree is after the harvesting of the fruits, during late winter or early spring when they are in dominant stage.

FLOWERING AND FRUITING:

The main blooming period for all the commercial species of the citrus in sub tropical climate is spring( March/April- after dominancy) when soil moisture and temperature are favorable. Sweet orange blooms 2 weeks earlier than mandarin.Citrus fruit develop very slowly and in a pattern of sigmoid curve. In Nepal it was observed that mandarin, sweet orange, lime, ureka lemon, rough lemon, fruits take about 32 weeks, 34 weeks, 22 weeks, 20-24 weeks and 32 weeks respectively.

HARVESTING:

Being non-climetric the citrus fruits fail to ripen and improve in taste after harvest. So, the fruits should be harvested only when they are fully ripe. A maturity index includes;

1-Minimum colors break on fruit surface

2-Balanced ratio between sugar and acid contents and sugar at its best.

3-Development of characteristics flavor and taste of the variety

YIELD:

Sweet orange/ Mandarin: 1000-1500 Fruits /Tree

Lemon: 500-700 fruits / tree

Lime: about 1000 fruits/tree

Pummelo: 100 fruits / tree

Grapefruit: 300-1000 fruits /tree

STORAGE:

While citrus fruits will keep for a couple of days at room temperature, the best way to store it is in the refrigerator. If you can find the space, the vegetable drawer is the best spot. It should keep there for several weeks. Don’t keep the fruit in a plastic bag or an airtight container, which can make it get moldy or soft faster. Mesh bags that let air circulate are fine. Look through the fruit regularly and use the ones that are getting soft.

MAJOR PROBLEM IN CITRICULTURE:

1-Citrus decline/Dieback

     Causes:

Soil factor 

Nutritional factors

Orchard management

Insect pests

Nematodes

Diseases

2-Granulation

It is the physiological disorder of the juice sacs of citrus fruits where they become comparatively hard, assumes a grayish color and become some what enlarged.

Factors affecting granulation

Climate: Humid climate

Species and cultivars: Sweet orange

Mineral nutrition: Boron and zinc deficiency

Enzymes and plant growth regulator: Higher level of auxins. Cytokines and abscissic acid and low gibbrellins.

Crop load: Heavy load

Control: Three spray of 25 ppm Boric acid, 1% potassium nitrate and 2% calcium hydroxide at monthly intervals starting from 10 september reduced granulation.

3- Fruit drop

A heavy shedding of flowers and fruits, right from the flowering stage to harvesting time occurs in citrus. It is common observation that not more than 7-8 % of flowers develop into mature fruit.

Post setting drop: A drop after fruit set due to over population and lack of pollination and fertilization.

Summer or June drop: This occurs in late spring or early summer when the temperature is high and air and soil air dry.

Pre-harvest drop: Drop of mature fruit due to auxins and gibbrellins deficiency.

Physiological cause of fruit drop:

Lack of pollination and fertilization.

Hormonal imbalance 

A very hot or dry speel for a long period.

Lack of adequate moisture in a soil.

Insects pests like citrus bud mite, mealybug, fruit flies and disease.

Control: Spray 10 ppm of 2,4-D IN September about 2 months before harvesting.

INSECT PESTS:

1)Citrus psylla( Diaphorina citri)

Damage is caused by the nymphs and adults which suck sap from buds and tender leaves

It also acts as a vector of greening disease

     Control:

Prune affected shoots and destroy.

Spray Monocrotophos(0.05%) or Dimethoate (0.05%) or phosaline (0.05%)

First spray should coincide with emergence of new flush. Repeat once or twice at 10-12 days intervals.

2)Leaf miner( Phyllocnists citrella)

Adults moths are small white 

The eggs are laid on tender leaves.

The larvae feed on the epidermis of tender leaves making serpentine mines which are silvery in color.

      Control:

Prune affected shoots and burn.

Spray Monocrotophos(0.045%) or Dimethoate ( 0.03%) during initation of new flush.

3)Whiteflies(Dialeurodes citri)

Nymphs and adults suck sap from ventral side of the tender leaves, excrete honeydew and encourage the development of sooty mould.

      Control: 

Avoid dense planting and stress on the plants.

Destroy infected plants part

Spray Phosphamidon( 0.05 %) or Dimethoate (0.045%).If required spray once or twice at 10-12 days interval.

4)Lemon butterfly(Papilio demolius)

The caterpillars which are brownish black at initial stage and green at mature stage feed on tender leaves and defoliate the entire trees.Young plants in nursery are seriously affected.

       Control: Clip-off the affected leaves with cate rpillars and destroy. Spray 0.1% carbaryl.

5)Fruit Flies( Dacus dorsalis)

Fruit flies puncture the rind of the fruit at the pre harvest stage and lays eggs inside the fruit.

         Control: Collection and destruction of infested fruit reduces the insect population.

DISEASES:

1)Foot rot or Gummosis

The disease is caused by a soil- inhabiting fungus( Phytopthora spp) which attacks the trunk of the tree. 

The symptoms appear as yellowing of leaves, followed by cracking of bark and profuse gumming on the surface.

This causes the bark to rot and the eventual die back of the tree.

2)Citrus canker 

Bacterial disease caused by Xanthomonas axonopodis pv citri.

Citrus canker is mainly a leaf spotting and rind blemishing disease.

Pruning of affected twigs before the onset of monsoon and spraying with 1% of Bordeaux mixture at periodical intervals can check this disease.

3)Citrus tristeza virus

The most efficient vector is T.citricida( the brown citrus aphid).

Common symptoms include reduced fruit size, leaf vein clearing, yellowing and cupping of leaves and stem pitting.

 

4)Sooty moulds

Caused by Capnodium citris. Black colored sooty mass can be seen covering the leaf surface and sometimes on young stems and fruits surfaces.

Spraying systemic insecticides like to manage the insects population can also help in avoiding or reducing sooty mould.

5)Mosaic( Transimitted by grafting)

Affected leaves and fruits with yellow and green patches.

Use virus free planting material.

Control aphid vector through insecticides.