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Citrus Area Under Cultivation Citrus is cultivated in the states of Maharashtra, Andhra Pradesh, Punjab, Himachal Pradesh, Uttar Pradesh, Madhya Pradesh, Karnataka, Jammu and Kashmir, Orissa, Gujarat, Assam, Meghalaya, Rajasthan, Sikkim and Tamil Nadu.

Botanical Name : Citrus sp. Family : Rutaceae Plant Discription : It is an evergreen medium to tall, erect tree .It grows to maximum height of 25m . Trees are thorny and bear flowers singly or in clusters which bear fruit generally round to oval in shape depending on the species.

Centre of Origin : Varied according to the variety Pollination System : Cross pollinated Chromosome No. : 2n=18 Nutritional Levels : Moisture (%)

Protein (%)

Fat (%)

Mineral matter (%)

Fibre (%)

Carbohydrate (%)

Calories (K Cal)

85

1

0.9

0.3

1.7

11.1

0

Phosphorus (mg/100g)

Potassium (mg/100g)

Calcium (mg/100g)

Magnesium (mg/100g)

Iron (mg/100g)

Sodium (mg/100g)

Copper (mg/100g)

10

270

70

0

0.26

0

0

Manganese (mg/100g)

Zinc (mg/100g)

Sulphur (mg/100g)

Chlorine (mg/100g)

Molybdium (mg/100g)

Cromium (mg/100g)

19

0.07

0

0

0

0.007

Carotene (mg/100g)

Thiamine (mg/100g)

Riboflavin (mg/100g)

Niacin (mg/100g)

Vitamin C (mg/100g)

Choline (mg/100g)

Folic acid-Free (mg/100g)

0

0.02

0.01

0.1

39

0

0

Minerals

Vitamins

Folic acid- Total (mg/100g) 0


Citrus Diseases Foot Rot or Gummosis (Phytophthora spp.) The symptoms appear as yellowing of leaves, followed by cracking of bark and profuse gumming on the surface. The main source of infection is infected planting material. As a result of severe gumming, the bark becomes completely rotten and the tree dries owing to girdling effect. Prior to death, the plant usually blossoms heavily and dies before the fruits mature. In such cases, the disease is called foot rot or collar-rot. Control : Preventive measures like selection of proper site with adequate drainage, use of resistant rootstocks and avoiding contact of water with the tree trunk by adopting ring method of irrigation are effective. Alternatively the disease portions are scraped-out with a sharp knife and the cut surface is disinfected with Mercuric chloride (0.1%) or Potassium permanganate solution (1%) using a swab of cotton. Painting 1 m of the stem above the ground level with Bordeaux helps in controlling the disease. Also spraying and drenching with Ridomil MZ 72@ 2.75 g/l or Aliette (2.5 g/l) is effective in controlling the disease.

Ganoderma Root-Rot (Ganoderma lucidum) The disease appears in the soil in one or more of the lateral roots. Whitish strands of fungus spread along the surface of the bark of the roots, which later turn dark. Gradually, the fungus spreads to the bottom of the main trunk. The affected tissues become very light, swollen and spongy due to water accumulation. During rainy season bracket-like fungal fructifications appears at the base of the trunk. Control : Removal of dead or decaying old stumps from the orchard, treating the basal portion of the stakes with a fungicide and periodical collection and destruction of brackets near the collar controls the disease. Isolation of infected trees by digging a trench all-round the tree to prevent the diseased roots from having contact with the healthy roots and mixing. 0.5 to 1 kg of powdered Sulphur with the soil in the trench helps in controlling the disease. Application of Aureofungin solution (1.5 g in 5 litres of water) and Vitavax (500 ppm) in plant basin is effective

Dry Root Rot (Macrophomina phaseoli, Fusarium spp. and Diplodia natalensis) It is characterized by moist decay of the bark in the early stages and a dry shredded condition of the bark with hard, dead wood underneath in later stages. The affected roots emit bad odour. Affected tree defoliates, and produces heavy crop of small-sized fruits. Control : If the taproot and crown are still in good condition and only one or two roots are affected, the diseased roots should be cut off and destroyed. The cut surface should be painted with Bordeaux paste.


Pink Disease (Pellicularia salmonicolour) Usually the disease appears during or just after monsoon rains. In the early stages branches and leaves wilt and die. The affected branches are covered with a fine silvery-white film of mycelium. From the characteristic pink colour produced by the fungus on the branches, the disease is aptly called the pink disease. When the bark is severely infected it gets shredded, and the wood is exposed. Longitudinal cracking and gumming of the branches may also take place. Control : All the diseased portions should be trimmed and the cut ends painted with Bordeaux paste. Spraying of Bordeaux mixture (5-5-50) mixed with crude oil emulsion destroys the mycelium in the crotches.

Leaf Fall and Fruit-Rot (Phytophthora palmivora ) Shedding of leaves starts from the lower branches of the tree. The affected leaves show water-soaked patches. By the time these lesions extend to the whole leaf, the affected leaves drop off. The fruits in different stages of development are also infected. In the beginning, water-soaked patches develop on the rind and later these fruits drop off and rot. Control : Spraying Bordeaux mixture (1%) can effectively control the disease. Two sprays, one before the onset of monsoon in June and the second one at the end of monsoon in August or September are effective.

Scab (Elsinoe fawcetti) The lesions in early stages appear on the underside of the leaves as small semi-translucent dots, which finally become sharply defined pustular elevations. In later stages, leaves often become distorted, wrinkled, stunted and deformed. On the fruit, lesions consist of corky projections, which often break into scabs. The opposite surface corresponding to the warty growth shows a circular depression with a pink to red center. Control : The diseased leaves, twigs and fruits should be collected and destroyed. Spraying of Bordeaux mixture or Blitox (0.3%) is quite effective

Powdery Mildew (Acrosporium tingitaninum) Whitish powdery mass develops on the young leaves and twigs. Affected leaves get distorted. When the disease is severe the affected leaves drop off and the twigs show dieback symptoms. Surface of the young fruits is also covered by fungus, and they drop of prematurely. Consequently reducing the yield. Control : Powdery mildew can be controlled easily by spraying Wettable Sulphur (1.5kg/200 litres of water). Sulphur dusting (20kg/hectare) in the morning hours controls the disease effectively. Systemic fungicides like Bayleton (1g/litre of water) or Calaxin (3-4 ml/10 litres of water) or Benomyl (5g/10 litres of water) offer better and prolonged control of the disease.


Anthracnose or Wither Tip (Colletotrichum gloesporioides and Gloeosporium spp.): The fungus often attacks leaves young shoots and tender fruits. Affected leaves show necrotic patches with distortions. Dead parts of the twig assume silvery grey appearance. Flower buds, when affected fail to set into fruits. Infection on fruits results in fruit drop. Control : The orchard should be kept in healthy state by adequate irrigation, manuring and pruning the diseased twigs. Spraying Bordeaux mixture (1%) or Blitox (2.5g/litre of water) or Mancozeb (2g/litre of water) is effective in controlling the disease.

Twig Blight (Diplodia natalensis and Fusarium spp.) In the case of Fusarium twig blight, leaves dry up and shed. Small twigs die back from tips and show gummy secretion at the base of the dead twigs. In the case of Diplodia twig blight, the affected twigs show the pycnidial fructifications of fungus. Malnutrition and unfavourable environmental conditions are believed to be cause of the disease. Control : Pruning of the dead twigs and spraying with Benomyl (2.5g/ litre of water) is effective in controlling the disease.

Sooty Mould (Capnodium citri) The disease is common in the orchards where mealy bug and scale insects are not controlled efficiently. Black velvety coating on the leaves, twigs and fruits is the characteristic of disease. The coating is superficial and can be pulled of easily from leaf. Under dry conditions the affected leaves curl and shrivel up. Control : Disease can be controlled by pruning the affected branches and destroying them. Insects causing the disease can be controlled by spraying of Wettasulf (0.2%)+ Metacid (0.1%)+ gum acacia (0.3%) in the month of May. Once the insects are eliminated, sooty mould automatically disappears for lack of suitable medium to propagate.

Storage Rots Green Mold ( Penicillium digitatum ) : The fungus penetrates the fruit rind through wounds. Symptoms begin as water-soaked area at the fruit surface followed by growth of colorless mycelium and sporulation (green color). Blue Mold (Penicillium italicum) : The fungus penetrates through the uninjured peel and can spread from one fruit to adjacent fruit. Symptoms are similar to green mold except that the spores are blue. Altenaria Rot (Alternaria citri ) : Fungus enters the fruit through their buttons. Preharvest treatment with gibberellic acid or postharvest treatment with 2,4 D delay senescence of the buttons and subsequent decay by Alternaria.


Control : Storage rots can be avoided by careful handling during harvesting to minimize cuts, scratches, and bruises. Treatment of fruits with Bavistin (1000 ppm), maintenance of optimum temperature range and relative humidity and exclusion of ethylene during transport can reduce post harvest losses.

Citrus Canker (Xanthomonas citri) It is the most serious bacterial disease of sour lime during rainy season. The disease symptoms appear on leaves, branches and fruit stalks. Canker lesions appear as yellowish spots, which gradually enlarge and appear as raised, rough brownish pustules. These pustules are surrounded by a characteristic yellow halo. Canker lesions on the fruits are confined to the rind only and do not penetrate into the flesh of the fruit. The market value of the canker-affected fruits is very much reduced. Control : Pruning and burning all the canker-infected twigs before monsoon and disinfecting the cuts with Bordeaux paint can prevent the further spread of disease. Three sprays of Streptocycline 100 ppm (10 g of Streptocycline + 5 g Copper Sulphate in 100 litres water) or Blitox (0.3%) or neem cake suspension (1 kg in 20 litres water) during February, October and December can control the disease.

Tristeza Virus Disease The aphid (Toxoptera citricida) transmits Tristeza virus disease. The symptoms begin with the dieback of small branches and twigs, yellowing of leaves and heavy bearing of small fruits. As the disease advances the symptoms, intensify resulting in severe chlorosis and mottling. The feeder roots of the affected plants die, the bark of the larger roots is distorted and brittle, and dry rot symptoms are observed in case of lateral roots. After 7-8 years the branches of the affected plant dry up completely and the plants wilts completely. Few trees show wilting symptoms overnight and completely dry up in 2 or 3 days. Hence, Tristeza is also called a quick decline disease. Control : Good cultural practices, increasing the fertility levels of the soil and good drainage are useful in reducing the decline disease. The best method to check this disease is to control the aphid population by application of insecticides in the nursery and also in plantations.

Greening This disease is spread through grafting and citrus psylla (Diaphorina citri). Affected trees are stunted with pronounced leaf and fruit drop. Some branches on affected tree exhibit severe twig dieback symptoms whereas the others are apparently normal. The fruits of affected trees remain mostly green even on maturity and the fruits, which are directly exposed to sun show a conspicuous yellow patch on the rind surface. Disease fruits are valueless owing to small size, distortion, low juice and insipid taste.


Control : As the disease is transmitted through grafting, the budwood used from the parent tree should be free from greening. Controlling the vector population can effectively check this disease in the field. Spraying Phosphamidon (0.025%) or Parathion (0.025%) controls nymphs and adults. Soil application of Dimethoate 10% granules around the plant basin gives effective control of citrus psyllids.

Citrus Exocortis Exocortis is characterized by drying narrow strips of outer bark, which tend to separate from the inner live-bark. The outer bark slowly peels off as it withers. The affected trees show lack of vigour resulting in dwarfing. Control : The disease can be prevented by the use of virus-free budwood. Grafting tools should be disinfected after pruning branches from diseased trees.


Citrus Disorders Fruit Splitting This is mainly a physiological disorder and is largely attributed to high atmospheric humidity following heavy rains or heavy irrigation during hot weather. Two types of splitting, namely radial and transverse have been noticed. Radial cracking is more common than transverse one. Partial splitting is more prevalent while splitting down to inner core is rather rare. Often the cracked surface of the fruit gets infected by disease causing organisms such as Aspergillus, Aalternaria, Fusarium, and Penicillum which lead to partial rotting and early fruit dropping from trees. Control : The disease can be minimized by frequent and light irritations during the dry and hot periods and early picking of fruits soon after maturity.

Fruit Drop The causes attributed to fruit drop in citrus are lack of fertilization, mechanical shock, insects, disease, high temperature, rainfall, and defective irrational practices. The most pronounced stages of fruit drop occurs when the fruits are at marble stage. It lasts for a month after full bloom. On the onset of hot summer weather during May-June the second wave of intense fruit drop occurs while pre-harvest drop occurs during ripening period, which lasts from August-January. Control : The method of control depends upon the causes of the drop and the variety of the fruit. In order to reduce the pre-harvest drop, NAA (10 ppm) is sprayed from August till October at monthly interval.

Citrus Dieback/Decline Citrus dieback or orchard decline is a gradual deterioration process exhibiting loss of vigour, death of twigs and branches, reduction in yield and ultimate death. Many factors such as unsuitable soils, drought, lack of systematic manuring, general neglect, use of infected budwood and field incidence of vector-bore virus disease contribute to this declining condition singly or in combination. There is no external remedy to check viruses. It is, therefore, absolutely essential to manage the citrus orchards with utmost care. Control : Adopting a package of practices such as selection of proper site and soil, raising of genuine and healthy plants from certified bud wood, use of proper rootstock, judicious irrigation and manuring and scientific spray schedule against insect pests and diseases can successfully control the disease.

Oleocellosis It is caused by rind oil release when oil cells get ruptured during harvesting or during handling from the field to the pack house. It is more common in crop taken in 'Mrig' bahar and harvested during FebruaryMarch. Careful harvesting and handling reduces incidence of oleocellosis. Rind oil from ruptured cells discolours the skin making the fruit unmarketable. Control : Best way to reduce its incidence is to cure the fruit overnight at a temperature of 18-20O C for 12-24 hrs, before the fruit is moved from the field to the pack house.


Citrus Harvesting th

Normally the bearing starts from 4 year onwards. However, the commercial yield can be obtained from 6th year onwards. Maturity of citrus fruits depends upon the climatic condition, scion-rootstock and management practices. The period of maturity is shortest in lime (5-6 months), longest in mandarins and sweet oranges (9-10 months) which is further influenced by heat and moisture. The maturity in sweet orange (Citrus sinensis) is indicated by the change of the skin colour from dark green to light yellow. The outer skin get shiny appearance and the oil glands are visible. The hard texture of the rind becomes softer on maturity. Mandarin orange (Citrus reticulata) is harvested when 75% of fruit surface colour changes from dark green to yellowish orange. Limes (Citrus aurantifolia) and lemons (Citrus limon) are harvested when the colour of the skin changes from dark green to yellowish green. However, in all citrus fruits apart from the colour the TSS: acid ratio should also be considered. Normally the citrus fruits are harvested when ripe, as their quality does not improve on storage. Clippers or secateurs should be used to remove the fruit from the tree leaving a little portion of the stem attached to the fruit. Fruit should not be pulled by hand, as it ruptures the skin of the fruit and provides an entry point for field diseases. The harvested fruits should be placed in picking bags or plastic buckets and transferred to a shady place or packing house.

Yield th

A well maintained sweet orange orchard yields 600-800 fruits/plant/year from 8 year onwards, while that of Nagpur Mandarin of same age yields 800-1000 fruits/plant /year. In case of lime, a seven year old lime plant yields 1000-1200 fruits/year.


Citrus Intercultural Operations Weed Control In citrus orchards weed control is carried out by 2 or3 cross ploughing. While resorting to manual weeding tillage should not be deeper than 10 to 15 cm. Deep tillage once or twice in a year is more harmful than regular deep tillage. Diuron at 3 kg/a.i. /ha or Simazine (4kg a. i./ha) when sprayed during end of May controls dicot and monocot weeds in the orchard. The application may be repeated at 120 days for complete control of the weeds.

Intercropping The interspaces between the rows can be utilized in the initial 3 - 4 years for growing short term crops like Mung, Black gram, groundnut, soybean and vegetable crops. During the rainy season green manuring crops are grown and plowed into the soil before flowering. The choice of intercrop depends on local condition and climate. However indiscriminate cultivation of exhaustive intercrop should be avoided. Intercropping in Nagpur mandarin plantation should be avoided as it increases pest and disease incidences and even micronutrient deficiencies.

Training and Pruning In Citrus pruning is done to develop a strong framework in the beginning. Branches growing upto 45 cm from the ground are removed leaving a clear straight stem. 4 or 5 well-spaced branches are retained forming a thick bushy crown, which protects the stems and branches from the effects of sunshine. The bearing trees require support, as due to heavy bearing the branches tend to break. Usually the support is given by erecting a bamboo frame around the plant at a height of 2 - 2.5 m and the branches are tied with the help of rope to the structure.

Regulation of Flowering (Bahar Treatment) Due to the absence of low temperatures in Central India, The natural flowering of citrus trees is of very less intensity. Therefore the flowering is usually forced by withholding irrigation water. For forcing the trees to flower during February-March (ambebahar), the water supply to the trees is withheld for 40 to 60 days, i.e., from 15th November to end of December until the leaves show symptoms of temporary wilting. For mrigbahar (July flowering), about 40 to 50 days water stress (25% leaf drop) during May-June is sufficient to force the trees to flower.


Citrus Irrigation Water management constitutes an important input in citrus orchard, which determines productivity and longevity. Citrus plants responds well to irrigation. The critical period for irrigating citrus trees is during summer when frequent light irrigation helps to lower soil temperature and to raise humidity. In fact, irrigation should be so scheduled that the plants are watered few days before the onset of flowering and it is repeated again after the fruit-set. Application of irrigation is equally important at the time of fruit maturity so as to avoid shrinkage of fruits and drying of pulp. Shortage of water during these two stages may result in the shedding of flowers and newly-set fruits. Water stress during the later part of fruit development period reduces fruit size, but certain amount of stress during this period increases TSS, juice and vitamin C contents in the fruits. Watering at 5 to 6 days interval during summer and every 10 to 12 days during winter is quite effective. Drip irrigation is becoming popular in water scarce area of Tamil Nadu, Maharashtra and Andhra Pradesh. Use of drip system improved the yield, uniformity in fruits and gave excellent quality of fruits with respect to shape, colour and edible quality. Sprinkler irrigation avoids the harmful effects caused by excessive supply and also saves water. Sprinkling needs 30% to 50% less water than surface irrigation.


Citrus Pests Citrus Psylla (Diaphorina citri) : Both the adults and nymphs of this pest suck the sap from the tender parts of the buds, leaves, branches and injects a toxic substance into them. In case of severe attack leaves get distorted, curled up and ultimately fall resulting in complete defoliation of the plant. This pest acts as a vector for spreading the 'greening' disease. Control : A number of natural enemies such as species of coccinellids and ladybird beetles attack the nymphs of citrus psylla. The pest can be satisfactorily checked by spraying the plants with Phosphamidon (0.025%) and Parathion (0.025%). Also application of Monocrotophos (0.025%) or Malathion (0.03%) or Dimethoate (1.5%) is useful.

Bark Borer (Inderbela tetraonis, Inderbela quadrinotata) : The caterpillar makes holes into the branches and weakens the tree. Presence of webby mass of chewed wood particle and excreta of larvae conspicuously plastered on tree trunks is the clear indication of damage by these borers. The feeding of these pests causes interruption in translocation of cell sap, which adversely affect the growth and fruiting of the plant. Control : The pest is satisfactorily controlled by removing the webbing followed by plugging the holes with Cotton wool soaked in the 2-5ml of Dichlorvos 76EC solution (20ml/10 litres of water). The holes are then sealed with mud. The best time for its control is September-October and the operation should be repeated in January-February.

Citrus Leaf Miner (Phyllocnistis citrella) : This pest causes damages both in nursery and in grown up stages of the citrus plant. It the larvae attack tender leaves and feed in the epidermal layers of the leaf by making serpentine mines in which air gets trapped and gives them silvery appearance. The affected leaves turn pale yellow, get distorted and crumpled. Such leaves gradually dry and die away. The attack of this pest also encourages the development of citrus canker disease. Control : To keep the pest population under check, pruning of all the affected parts during winter should be done. Spraying the plants with Methyl Demeton (0.03%) and Phosphamidon (0.035%) at the emergence of new leaves is highly beneficial. Application of Phorate 10 G (2.5 kg a.i./ha) applied one day before planting is effective in reducing the larval population of leaf miner.


Citrus White Fly/ Citrus Black Fly (Dialeurodes citri; Aleurocanthus woglumi) : These insects suck the sap of the plants and during this process, secrete honeydew due to which sooty mould develops on the leaves. Sometimes, the infestation is so severe that the whole orchard looks black. Fruits turn black in colour and have insipid taste. The attack is more intense on the shady side of the tree. Drenching the trees with sufficient solution (preferably 8-10 litres for fullygrown tree) of either Monocrotophos (1.5 ml/litre of water) or Phosphamidon (0.7 ml/litre of water) or Acephate (0.8 ml/litre of water) controls the pest effectively.

Aphids (Toxoptera citricida) : The aphids suck the cell sap from the leaves. They also feed on the new shoots and tender fruits. Curling of infested twigs and leaves is a common symptom. The aphids are considered to be significant vectors of Tristeza virus. Control : Population of this pest on citrus can be easily controlled by spraying the plants with Parathion (0.03%) and Malathion (0.03%). Also Monocrotophos (0.025%) or Phosphamidon (0.035%) effectively control this pest. Spraying should be immediately undertaken as soon as the pest is observed.

Citrus or Lemon Butterfly (Papilio demoleus) : It is the most destructive pest in nurseries. The caterpillars feed on the young foliage at the nursery stage and also on young flushes of grown up trees. The caterpillar feed voraciously on leaf lamina leaving behind only the midrib. In case of severe infestation, entire tree is defoliated. The fully grown caterpillars are green in colour. Control : Hand picking of the larvae and spraying with Endosulphan 35 EC (2ml/10 litres of water) is effective in controlling the pest.

Fruit Sucking Moths : The moths are nocturnal in habit. During the daytime, they hide in fallen leaves and in weeds and become active at dusk and swarm in large numbers when citrus fruits are about to ripen. The moths continue feeding throughout the night and cause colossal damage. They pierce the ripened fruits and suck the juice from them. Such fruits are exposed to the secondary infections of diseases and infestation of flies. The affected fruit usually falls within a few days. Control : Elimination of alternate hosts plants from the vicinity of the orchards and collection and destruction of affected fruits reduce the pest population. Uses of poison baits have proved useful. Effective bait may be prepared by mixing 15g lead arsenate and 450g molasses in 10 litres of water. A little vinegar may be added to it and the bait should be suspended from trees in shallow wide-mouthed containers.


Citrus Mite (Eutetranychus orientalis) : The mites damage the fruits by causing russetting and renders the fruits unfit for export. The insects feed on the leaves and produce multiple grey spots. The affected leaves defoliate. Control : Mites can be controlled by application of Dicofol (1.5 ml/litre of water) or Wettable Sulphur (3.0 g/litre of water) or Monocrotophos (1.5 ml/litre of water).

Scale Insects : Armoured scales (Aonidiella auriantii, A. citrina, A. orientalis, Chrysompahlus aonidum.). Soft Scales (Coccus hesperidium, C. viridis). Citrus scales are of two distinct types-armoured scales, which have hard cover separate from the body providing protection to the body underneath. The soft scales the have no separate cover but sometimes a hard skin or a protective waxy secretion. The armoured scales damage the fruits and form as blemishes at low levels of infestation and in sever cases, they damage the tree badly. The soft scales secrete honeydew on which sooty mould fungus grows. A soft scale become serious when there is poor light penetration due to over crowding and waterlogged conditions. Control : Hard armoured scales are difficult to control. However soft scales are effectively controlled by spraying Monocrotophos (0.1%).

Fruit Flies (Dacus dorsalis) : Fruit flies puncture the rind of the fruit at the pre-harvest stage and lays eggs inside the fruit. The maggots hatch from the eggs and feed on the fruit pulp the affected fruits fail to ripen and drop prematurely. Control : Collection and destruction of infested fruits reduces the insect population. Use of flytraps containing 1% Methyl Eugenol and 0.5% Malathion mixed with sugar syrup two months prior to harvesting is effective.

Citrus Nematode (Tylenchulus semipenetrans) : Infestation of nematodes is one of the main factors responsible for slow decline of citrus. Damage caused by a citrus nematode infestation depends on the age and vigor of the tree, density of the nematode population, and susceptibility of the rootstock. Mature trees can tolerate a considerable number of these nematodes before showing lack of vigor and decline symptoms. In heavily infested sites, young trees may be stunted or fruit production may be reduced on bearing trees that have susceptible rootstocks. The damage is greater when trees are predisposed by other factors such as Phytophthora root rot and water stress.


Symptoms of nematode damage above the ground are lack of vigor, twig dieback, decline in growth, and reduced fruit size and yield. Nematode infestations may occur without inducing any aboveground symptoms. Under ground symptoms of citrus nematode infestation include poor growth of feeder roots and soil adhering to roots giving them a dirty appearance. Control :Good sanitation practices are essential to avoid nematode infestations. Use certified nematode-free material for planting. Rotation with annual crops for 1 to 3 years before replanting citrus helps to reduce citrus nematode populations. Using a resistant rootstock is recommended whether or not nematodes are present. Trifoliate orange is known to be tolerant to citrus nematode. Soil application of Neem cake and chemicals like Temic 10G (4 kg a.i./ha) are used successfully to control the nematodes. Intercropping of Marigold has repellent action and reduces the population of nematodes in citrus.


Citrus Post Harvest Technology Grading The fruit are inspected and unripe, immature, undersized, damaged or decayed fruits are discarded. For local markets, the citrus fruits are graded as per the size into small, medium and large grades. The differences between categories will depend on the type of fruit. For exports of Nagpur mandarins, the various grades recommended are as follows Grade Size No. of Fruits/ 10 Kg Packing (mm) 50-55 50-60

115

60-65

84

65-70

76

70-75

64

98

Packaging Citrus fruits are packed in sacks, bags, bamboo baskets and wooden boxes for sending to local markets. For urban markets, citrus fruits are packed in telescopic cardboard boxes. Corrugated trays are equally effective as packaging material while transporting the fruits. Use of such trays is cost effective due to its reusability. For export of Nagpur mandarin, usually 2 piece, telescopic, corrugated fibreboard boxes of three ply or five ply should be used. The size of the box may vary according to the requirement of the importing country. Normally a box size of 49.5 x 29.5 x 17.5 cm having 10 kg capacity is recommended. The boxes must have 5% area punched as holes for ventilation. To immobilize the movement of fruits inside the box, three ply wax treated dividers having ventilation holes are used.

Storage After the fruits are harvested, they should be treated with wax to reduce post harvest damage. Treatment of fruits with Bavistin (1000 ppm) can reduce post harvest losses and extend the shelf life to 25-26 days even at room temperature. Shelf life of Nagpur mandarin can be extended by three weeks on wrapping the fruits with heat shrinkable polythene and Cryovate film (D 955 and BDF 2001). The ideal storage temperatures for Nagpur mandarin is 6-7 OC at 85-90% relative humidity while O lime & lemon are stored at 10-12 C with 90-95% relative humidity.


Transport Citrus fruits are transported by rail or road as ordinary cargo and without refrigeration, which often leads to heavy loss due to decay and fungal infections.

Cool Chain Cool chain is essential during the transport of export quality commodity all the way from the farm to the customer. This helps in maintaining the temperature inside the box at the same low level as in the cold storage. The various stages of the cool chain are : 1. Coldstore at the farm. 2. Refrigerated truck from farm to the airport 3. Coldstore at the airport. 4. Building up of the pallet in a coldstore at the airport. 5. Loading the aircrafts directly from the coldstore in a short time. 6. Cargo aircraft maintains coldstore temperature in hold. 7. Off loading direct into a coldstore in the receiving country. 8. Refrigerated truck to the customers.


Citrus Planting Season of Planting The ideal time for planting the grafts is during June - July just after the first monsoon showers.

Spacing Spacing adopted for planting citrus varies depending on variety and agroclimatic conditions. However in general the following spacing are adopted. Citrus

Spacing (m)

Sweet orange (Mosambi )

6x6

Orange (Coorg and Nagpur mandarin)

6 x6

Lime and Lemon

5 x5

Method of Planting The grafts are planted by making a small hole in the centre of the pit sufficient to accommodate the soil ball. Care should be taken to keep the bud union at least 15 cm above the ground level. The soil around the plant is pressed gently. Planting should be immediately followed by irrigation. In case of high wind velocity the plants are tied to the stake.


Citrus Propagation In India citrus trees are propagated both by seeds and vegetative means. Seed propagation is still practiced in the case of acid limes and to produce rootstocks for budding purposes. Shield or T budding is the most commonly used method of vegetative propagation. Budding is generally done either in spring or in September.

Sheild or T Budding In this method of propagation, a bud from desired variety (scion) is transferred on the rootstock with an objective of utilising the vigorous root system of the rootstock and combining the best characters of both. A plump, but not too elongated bud is selected from the middle section of the scion shoot. It is removed by making an incision around the bud with the help of sharp budding knife. On the selected rootstock T-shaped incision is made just enough to accommodate the bud. The bud is inserted in the incision and tied with a strip of plastic film in such a way that the tip of the eye remains open. Budding should be preferably done as low as possible on the rootstock. It takes three to four weeks for the bud to unite when the new shoot from the grafted bud is about 10 cm long the top portion of the stalk above the union is cut off and the plastic film is removed. For budding, proper selection of the rootstock is very important as it contributes to the vigour, productivity and quality of fruits. It also influences resistance and tolerance to certain diseases and pests and plays a major role on agro climatic adaptation.

Rootstock

Characters

Rough lemon

Suitable for light (sandy) and infertile soil, resistant to Tristeza virus. But it is most susceptible to cold and induces poor quality fruit

Sour orange

Suitable for silty, clayey and poorly aerated soils , improves the fruit quality and has high sugar and acid content, improve the fruit size

Cleopatra mandarin

Suitable for heavy soils

Trifoliate orange

Cold tolerant, improves the fruit quality and has High sugar and acid content, hasten fruit maturity and the fruit size. It also induces precocity. Resistant to Citrus nematode (Tylenchulus semipenetrans). It is ideal for high density plantations.

Sweet lime

It gives high yield in early age followed by reduction in the yield later on. Also it is most susceptible to cold and induce poor fruit quality

Sour lime

Most susceptible to cold


Rootstock

Characters

Rough lemon (Jambheri)

Vigorous rootstock. Induce poor fruit quality and resistant to Tristeza virus and drought and salt tolerant

Sweet lime

Give high yield in early age followed by reduction in the yield

Citranges

Resistant to Citrus nematode (Tylenchulus semipenetrans

Rangpur lime

Tolerant to Phytophthora foot rot and resistant to Tristeza virus , Drought and salt tolerant

Sweet orange

Resistant to Tristeza virus


Citrus Soil & Climate Soil It can grow in almost all types of soil having a pH range of 5.5 to 7.5 provided it is sufficiently aerated and allows taproots to penetrate to the desired depth. Citrus grow well in loam or sandy loam soils. Deep alluvial loams of Indo-Gangetic plains, the coarse friable black soils of Maharashtra and similar black soils of Deccan and murrum soils are considered excellent for growth of sweet oranges and mandarins. A deep uniform, loamy and well-drained soil is best for Nagpur Mandarin cultivation. Saline or alkaline soils and those having lime nodules should always be avoided for citrus.

Climate Citrus plants grow well in tropical and subtropical climates and can stand light frosts occasionally. The O O average temperature for good growth is about 16 to 20 C. Citrus can grow well between an altitude of 500m to 1000 m. It grows well in drier areas having rainfall upto 500mm to hilly areas having 2500mm of rainfall. The loose-jacket oranges prefer slightly higher elevations and tracts possessing relatively higher humidity. Mandarins prefer more humid and tropical summer climate with warm winter and high rainfall. However Nagpur mandarins are successfully cultivated in arid irrigated conditions of central India. Limes and lemons require warm and moderately moist conditions for its growth.


Citrus Varieties Name of the Variety/ Area

Characteristics

Rangpur Lime C. limonia Western and southern India

Rind and pulp are orange in colour. Rind is thin and adherence to pulp is moderate.

Kagzi Lime (Citrus aurantifolia) Maharashtra, Andhra Pradesh and Karnataka

Fruits are small to medium, pulp is juicy greenish with strong adherence to the skin; skin yellowish green, thin or papery and shin y. It is mainly used for processing purpose

Lemons (Citrus limon) West Bengal, Assam, and Uttar Pradesh

Fruits large, Ovoid to round, fruits dark green, rind thick adhering to the pulp, moderately juicy and acidic

Sweet Lime (C. limettioides) Punjab and Tamil Nadu

Fruit medium-sized, subglobose to oblong, base evenly rounded, apex commonly rounded, nipple is flat and surrounded by a shallow circular furrow ,rind thin, surface smooth with Prominent oil glands strong adherence of rind, colour greenish to orange-yellow on maturity, segments around 10 ,flesh colour straw-yellow, tender, very juicy, flavour insipid because of lack of acid

MANDARIN (Citrus reticulata) Khasi Orange Assam and Meghalaya

Fruits globose to oblate, surface smooth, colour orange-yellow to bright orange, rind thin with very little adherence, segments usually 10, pulp vesicles uniformly orange, texture coarse, juice abundant with well-blended flavour.

Coorg Orange Karnataka

Fruits oblate, Colour bright yellow and uniform, Rind Medium Thick with little adherence, segments usually between 9 to 11, pulp yellow with fine texture and abundant juice

Desi Punjab and Himachal Pradesh

Fruits ovoid, colour uniform golden yellow, rind medium thick somewhat thicker than that of Coorg mandarin ,segments usually between 7 to 10 ,pulp light reddish yellow, texture tender , sufficiently juicy and moderately flavoured but somewhat acidic in taste

Kinnow Orange Punjab

The fruit is medium-size somewhat oblate in shape, rind moderately thick adherence with the pulp quite strong although peelable surface smooth and glossy fruit colour yellowish orange at full maturity segments 9 to 10, firm pulp yellowish orange very juicy somewhat acidic. The variety is cold resistant.

Darjeeling Orange West Bengal and Sikkim

Fruits are comparatively smaller in size somewhat flat in shape colour yellowish to orange when fully ripe, rind thin, adherence little, juice abundant and sweet flavour.


SWEET ORANGE (Citrus sinensis) Mosambi Maharashtra and Andhra Pradesh

Fruit light yellowish orange in colour, surface rough with prominent streaks on the rind, oblate to spherical, apex broad, rind thick, well-defined segments numbering 9 to 12, peeling difficult, pulp light yellow; juice sweet.

Malta (Common) Punjab and Haryana

Fruit orange-yellow, surface smooth; shape spherical; medium to large in size; thickness of the rind medium, segments 10, well-defined; pulp orange, abundant juice, good flavour

Malta (Blood Red) Punjab

Skin yellow with scarlet blush. Rind is relatively thin, tight and glossy. Pulp corn coloured and red streaked, early ripening; pulp sweet, abundant juice, red coloured, pleasant flavour

Sathgudi Andhra Pradesh

Fruits are smooth and have attractive orange colour, shape spherical, size variable, rind medium thick, segments 10 to 12, pulp orange coloured abundant juice, good flavor.

Exotic Varieties USA Lemons-Processing Eureka, Allen, Cascade, Cook, Meek, Thorton, Lisbon, Bradbury, Cavors, Deavor, Hall, Jameson, Ledig, Limoneira,-8A, Monore, Prior, Prospect, Strong, Femminelo, Oval, Genoa, Brena. Sweet Orange-Table & Processing Purpose Valencia, Lue, Gim Gong, Pope, Cutter Frost, Olinda, St. Michael, Sanfords Meditteranean, Ruby, Kwatta 202. Orange-Processing Navel, Valencia Brazil Sweet Orange-Table & Processing Purpose Bahia, Cabula, Baianinha, Hamlin, Orvalin de Mel, Rubi, Valencia, Bahia. Sweet Orange-Processing Purpose Pera, Pera Olimpia, Corsa Tardia, Ovale San Lio, Lamb Summer. Sweet Orange-Table Purpose Caipira Mexico


Sweet Orange-Table & Processing Purpose Corriente France Sweet Orange-Table & Processing Purpose Blonde Australia Orange-Processing Navel, Valencia Japan Orange-Table & Processing Purpose Owari, Wase.


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