In India, citrus fruits ranks third in production after banana and mango. Among citrus crops, mandarin orange (Kinnow mandarin, Nagpur, Khasi, Darjling) covers the largest area followed by sweet orange(Musambi, Pineapple, Blood Red and Jaffa) andAcid lime. Among these, Kinnow mandarin bears the highest place in production, productivity, juice content and fruit quality.
Sweet orange and Acid lime are the two chief commercial citrus fruits grown in Andhra Pradesh. Lemons, Pummeloes, and Mandarins are cultivated in limited areas. Andhra Pradesh has, and area of 2,53,261 hectares under citrus producing 3.53 million tonnes annually and holds the first rank in acid lime production.
Climatic requirement for growing Citrus fruits
The state provides a congenial climatic condition for production of citrus fruits. Tropical climate with moderate rainfall, i.e., 750 mm and absence of strong winds are ideally suited to kagzi Lime and Sweet Orange. They can be grown successfully even up to an elevation of 900m above mean sea level.
A well drained loamy soil of uniform texture up to a depth of 2-3 m having good fertility is considered ideal for its cultivation. The plant is highly sensitive to the water-logged situation. Heavy soils, if well drained, yield good crops but the cultivation becomes difficult pH 6.5 to 7.5 ideal.
The water table should not rise within one meter from ground level. A high water table for permanent or fluctuating nature and low lying locations are unsuitable.
A) Sweet Orange
This variety is a high yielder and popular in South India. The individual tree bears 1000 to 2000 fruits. The fruit is almost spherical in shape and attractively colored when fully manure. It weighs 140 to 150 g. The base and apex are evenly rounded. The peel is thin and ragrery little. The segments are 10 to 12. A number of seeds 14. Brix 8.5o to 9o. Juirce 49%, acidity 0.65% and ascorbic acid 47 mg/100 g of juice.
Batavian variety (Bathayee) closely resembles sathgudi except for the green and yellow patches that develop due to basketing and mostly grown in coastal districts.
It is grown in some parts of Telangana. The fruit develops prominent furrows on the skin and a circular grove at the stylar end. It is having rough and thick skin and tastes sweeter and has more seeds compared to Sahgudi orange and it lacks flavour and inadequate blending of acidity with sugars. It is found to grow well and produce yields equal to Sathgudi. The fruit is spherical, smooth and weighs about 200g. The segments 14, brix 8.5O, acidity 0.44% and juice content 43%. The fruits are of good quality.
4. Acid lime
The variety commonly grown in the State is Kagzi lime which is susceptible to canker. Canker tolerant varieties, Balaji (By AICRIP, Tirupati) and Petlur selection (Pre-released variety by Citrus Research Station, Petlur) were developed. The annual yield varies from 3000 to 5000 fruits per tree. The fruit weighs 40 to 50g. It is spherical, smooth and develops attractive yellow color when fully ripe. The peel is very thin, adhering to segments. The juice sacs are slender and spindle-shaped, juice 47%, and brix 6 to 7O, acidity 6.8 to 7% and ascorbic acid 25 to 27 mg/100 g of juice. The average number of seeds is 12.
Red Fleshed: Pulp is red in color, brix 8%, acidity 0.7% and is sweet in taste.
Acidlime is propagation by seed and sweet oranges by budding. For raising seedlings, freshly extracted seeds should be sown, 2.5cm X 7.5 cm apart on raised seedbeds prepared from well pulverized and heavily manured soil with decayed leaf mold or well-rotted cow dung. The seeds are sown in May-June or September-October, and the seedlings will be ready for transplanting after 6 to 8 months of sowing. In a case of acid lime, when they attain pencil thickness. They are budded in case of sathgudi. Bud material should be procured from the virus free parent trees.
The seedbeds are taken care of to be free from damping-off by drenching the soil with 1% Bordeaux mixture/metalaxyl 3g/lit of water.
For Sathgudi orchards, one-year-old, healthy and vigorously growing budlings have to be selected. Rangapur lime rootstock is recommended for Sweet orange.
In the case of acid lime, pummelo and lemon (gajanimma) or rangapur lime rootstocks can be used.
Planting of Citrus
Pits of the 1-meter cube are dug in a square system at a spacing of 6m for acid lime and 6-8m for sweet oranges and filled with a mixture of tank silt, red earth, and farmyard manure. Two or three kilos of bone meal or super phosphate per pit need to ber applied. Planting of seedlings and budlings may be done after rainy season to avoid heavy rains and stagnation of water in the soil.
The plants selected should be free from viruses, pests, and diseases. While planting care should be taken to see that the bud-joint does not get into the soil. The plants have to be staked immediately to avoid wind damage.
Fertilizers for Citrus
|Age of the plant||Sathgudi & Pummelo||Acidlime & Lemons|
|5th year & above||1500||350||400||1500||600||800|
Nitrogen is applied in the form of FYM and oil cakes each at 25% and the remaining 50% with chemical fertilizers. While P2O5 in the form of superphosphate and K2O in the form of sulphate of potash. Manures are applied in 2 to 3 equal doses i.e. the first dose in December-January, 2nd done in June-July, 3rd dose in September, Potash application can be reduced if the soil is rich in this nutrient. A mixture of zinc sulphate 0.5%, manganese sulphate 0.2%, boric acid 0.1%, urea 1% and lime 0.4% has to be sprayed two or three times in a year to control chlorosis in leaves.
In severe cases of chlorosis, a composite spray of the micronutrients given below has to be sprayed on new flush.
Zinc sulphate … 5g
Copper sulphate … 3g
Magnesium sulphate … 2g
Ferrous sulphate … 2.5g
Manganese sulphate … 2g
Borax … 1g
Lime … 6g
Urea … 10g
Water … 1 lit
Purning and Taining
The plants should be trained to grow straight and to build a strong framework. Root-stock sprouts, water suckers, and dead wood should be removed periodically and the cut ends are smeared with Bordeaux paste.
During prebearing period short growing crops like groundnut, ragi, bajra, wheat, and vegetables (except solanaceous crops) can be profitably grown in the interspaces. In the bearing orchards green manure crops like sunn hemp, green gram, cowpea etc., are raised and incorporated into the soil during the monsoon period.
Irrigation of Citrus
Young trees have to be regularly watered throughout the year during the dry season. The practice of applying water close to the tree trunks should be avoided as it is conducive to the development of collar rot, gummosis and other fungal diseases. Double ring system of irrigation should be adopted for advantage. The basins may be enlarged from year to year so as to accommodate adequate irrigation water for growing tree. Under normal conditions, citrus plants required 18 to 25 irrigation per year. Depending on the climate citrus requires irrigation once in 7 to 15 days interval. But during the flowering and fruit maturity stage, there must be sufficient moisture in the soil. Otherwise there will be flower and fruit drop in the plantation.
After weeding and manuring, application of dry-leaf mulch or paddy husk to a thickness of 8 cm in the basin keeps down the weed growth and decreases the number of irrigations, while improving the fruit quality.
Shallow ploughing may be taken up during monsoon season to avoid damage to fibrous root system. The soil in the basin is likely to become hard under continuous irrigation, and therefore it should be given a light hand-digging with a spade after every three irrigations so as to maintain porosity and tilth. Under no circumstances should weeds be allowed to grow rampant in the orchard.
Control of Fruit drop
Early and pre-harvest fruit drop is common in citrus fruits. To control this physiological disorder, it is a better to give three sprays of 2,4-D at 10 ppm (1g/100lit), one at the time of flowering, the second one month after fruit set and the third one month before harvest which is beneficial and increases the yield considerably minimizing the fruit drop.
Harvesting and Post-harvest Technology of Citrus
Bearing starts from third year onwards in acid lime and 5th year onwards in Sathgudi. The sweet orange in South India produces two crops a year regularly with a variable third crop. The main harvest is from December to February and second one from June to September and the third one, if there is, in March to June. Limes are harvested throughout the year, but mainly, May to August (80%), January-August (14%) and September-December (6%), Pummeloes, between August-December.
Harvesting is done after full maturity of fruits only. During fully maturing stage there is a change of color of fruit, increasing in sweetness. Usually, a fruit will take 8 to 9 months time from flower to fruit measure stage in sweet orange. Whereas in acid lime it takes 4.5 months time. In sweet orange harvesting done once in change color from green to yellow indicated, whereas the in acid lime harvesting is done, once the fruit reaches fully, size, green color and kept in the stroge till the fruit color changes to yellow and send to the market.
During the harvesting care in taken to avoid damage to the fruit skin. Damaged fruits will have less price.
Storage and Marketing
Storage life of Sathgudi can be enhanced by dipping the fruits for 30 seconds in 2 to 3% wax emulsion mixed with 2,4-D at 50 ppm and air drying before packing. In the case of acid lime also the fruits can be similarly treated and packed in alkathene lined gunnies to increase the storage life. The fruits are then packed in gunnies to increase the storage life. The fruits are then packed in gunnies providing paddy straw before transport to distant markets. The sweet orange fruits can be preserved for longer periods of cold storage at 0 to 2OC and acid lime at 7 to 9OC in a relative humidity of 85 to 90%.
The citrus fruits are valued for the vitamin ‘C’ and phosphorus content. Several delicious fruit products like refreshing drinks, pickles, etc., are prepared. They are the main source for preparation of peel oil, citric acid, citrate of lime and cosmetics which have international market value.
A) Pests of Citrus
1. Leaf miner (Phyllocnistis citrella)
The caterpillar mines into the leaves of young flush, showing glistening and zig zag mines on them. The affected leaves curl, deform and the plant appears sickly.
Spraying of chemicals like monocrotophos 1.6 ml or fenvalerate 0.2 ml or imidacloprid (confidor 100 SL) 0.5 ml or profenophos 2 ml per liter of water immediately after the appearance of fresh foliage and 2nd spray after a week period is recommended. But care should be taken that the same chemicals should not be sprayed repeatedly.
2. Citrus leaf weevils (Myllocerus sp)
The weevils cut the leaves from margins
Spraying of monocrotophos 0.05% or carbaryl 0.15% two or three times at 10 days intervals.
3. Citrus butterfly (Papilio demoleous)
The caterpillar is severe in the nursery and young plantations causing defoliation of the young plants. It is dark grayish brown in color with whitish oblique patches when young.
Spray fenetrothion 0.05% or diazonan 0.05% or phosphamidon 0.04% or monocrotophos 0.04% @ 10-20 litres/tree.
4. Bark and Stem borer (Indarabela tetraonis)
The caterpillar bores into stems and branches and forms long galleries of silk overlaid with small fragments of wood and frass. The larva comes out from this gallery and feeds on the barks.
The wooden particles, silk and bored holes plugged with excreta should be cleaned and poured with Endosulfan or Malathion or Kerosene or Petrol using an ink pillar. Then the hole is sealed with clay so that the larva dies within the tunnel.
5. Green mites (Olygonychus citri, Tetramychus spp.)
Infested leaves from upper side become stippled and later on turn grey on yellow. Infested fruits remain often small in size and drop.
Spraying of water soluble Sulfer 3g or propargite 2ml or Dicofol 3.5 ml/lit of water two times in 10 days interval is recommended for mite control.
6. Mangu mites or Pinkish Brown Blotch (Phyllcoptes oleiverus)
The mite causes pinkish brown blotch on fruits, thereby reducing the market value of the fruit.
Spraying with Wettable sulphur 3g or Propargite 2ml/ Dicofol 3.5ml or Propargite 2ml per liter of water in September, October and November months, 3 times at monthly intervals is recommended. The spraying should coincide with the marble stage of the fruit.
7.Fruits sucking moths (Othreis maternal, O.fullonica, Achoea janata, O.ancilla)
These moths pierce the ripening fruits and suck juice. The affected fruits rot and drop. The moths will be active during dusk. The larvae develop on the weeds.
- Rotten and fallen fruits attract the adult moths. So affected dropped fruits should be collected and destroyed.
- Moths get attracted to light. So during fruit ripening period, light traps along with basins containing fruit juice + 1% sugar + 1ml Malathion or kerosene bait solutions are to be arranged here and there in the field. So that the moths get attracted to light, fell and die in the baited basins kept under the light traps.
- Bait prepared with 15g lead arsinate + 1kg jaggery or molassus + 5 liters of water with a little vinegar and kept in the field here and there to attract the moths.
- Just before the ripening period of the fruits itself bagging of fruits either with 300 gauge polythene bags or palm leaf bags helps to reduce the pest attack and in the same way the bagged fruits with alternate green and yellow marking look attractive to the consumers.
- The adult lives for 8 days, and it feeds only 6 days. In remaining 2 days it lays an egg on Menispermaceae family weeds on the field bunds. The larvae feed on the weeds and a pupal period is also completed on weeds itself. Only adults damage the sweet orange fruits. So, by destructing Menispermaceous weeds on field bunds and nearby places we can reduce the pest attack.
8. Aphids (Toxoptera citricidus and T.auranti)
The pest attacks the tender shoots, as a result of which the shoots get curled and growth checked. They also transmit Tristetza virus which causes decline of citrus.
Spray with Imidacloprid (confidor 200 SL) 0.5ml or Dimethoate 2ml per liter of water is recommended.
9. Citrus Psylla (Diaphornia city)
Adults and nymphs suck sap from flush as a result of which the leaf curls and flowers drop. Greening pathogen is transmitted by this insect.
Spray with Imidacloprid (confidor 200 SL) 0.5ml or Dimethoate 2ml per liter of water is recommended.
10. Mealybugs (Planococcus citri, P.pacificus, Icerya purchasi)
The mealy bugs infest tender shoots and fruits. Severe infestation causes premature fruit drops and affects plant growth. The presence of sooty mould and white mealy bugs no fruits and shoots are the symptoms.
Spraying of Methyl parathion 2ml or Monocrotophos 1.6ml per liter of water two times at 15 days interval is recommended.
11. Snow scales (Pinnaspis aspidistrae)
Small white insets in large Number colonize on all plant parts like fruits, leaves, branches, trunk, etc. and suck sap from them, thus devitalizing the tree.
It is recommended that the tree trunk is rubbed with pieces of gunny bags, then sprayed with Metasystox or Dimethoate 2ml per liter of water completely covering the damaged parts.
12. Termites (Odontotermes (Termes) obesus, Microtermes obesi)
Feed on roots and stem bases near the ground level. The severely infested trees often dry
Mud galleries on tree trunk should be scraped off and dusted with lindane powder or Chloriphyriphos solution @ 3-5 ml/liter of water should be well mixed with soil around the tree basins using hand hoes.
13. Red tree ants (Oecophylla smargdina)
Although these ants do not feed on any plants, they spread all over the trees and nests of leaves, thereby causing a great nuisance. Indirectly harmful by protecting aphids and coccids and hinders fruit harvest.
The ant nests on the tree should be disturbed and dusted with lindane powder to control the tree ants.
14. Nematodes (Tylenchulus semipenetrans , Meloidogyne spp.,)
Slow decline, dieback, rootlets shortened, swollen and irregular. Soil adhere to the gelatinous matrix of the egg mass, galls on roots, reduction in yield.
- Seedlings should be selected from nematode tree nurseries.
- During replanting of the nurseries, neem cake or castor cake or pongamia cake should be applied @ 60-80 kgs per one cent area.
- Do not grow solanaceous crops or bhendi, banana crops in citrus orchards.
- Apply 130-160g Furadon or 40-80g Thimmet granules per plant basin. After three months, based on plant age applies 15-25 kg neem or castor or pongamia cakes per plant for every six months.
B) Diseases of Citrus
Fungal diseases of Citrus
1. Leaf fall and Fruit rot (Akuralu or Kaya Kullu Tegulu) (Phytophthora palmivora)
Water soaked leisions develop on leaves and fruits, resulting in their drop.
Two sprays of 0.1% Bordeaux mixture, once before the beginning of monsoon and the other at the end of the monsoon are suggested.
2. Gummosis or Root-rot (Banka or Veru kullu Tegulu) (Phytophthora citrophthora, Phytophthora parasitica, Phytophthora palmivora)
The bark at the collar region peels off allowing gum exudation.
- Selection of proper site with adequate drainage.
- Graft union of the plant should be well above the soil (high budding: 30-46 cm or above).
- Double ring method, with an inner ring at about 45cm and an outer ring around the tree, should be followed. It prevents the irrigation water from coming in direct contact with the trunk.
- Scrape the gum portions of affected bark and apply Bordeaux paste or copper oxychloride paste on the affected portions. Apply of Bordeaux paste to the tree trunks up to 2 feet height is recommended once a year.
- Spray Carbendazim (1%) on twigs and branches twice at 15 days interval to prevent Diplodia
3. Diplodia Gummosis (Diplodia Banka Tegulu) (Diplodia natalensis)
The affected branches show oozing of gummy substance out of bark splitting.
Similar treatment as in root rot is suggested.
4. Dry Root rot (Fusarium solani)
Infected roots become blackened and the bark portion of the roots easily peeled off from the root. Infected plant shows heavy flowering, and fruiting and the plant die before the fruits reach maturity stage.
Root rot in acid lime and sweet orange can be controlled effectively when the plants are detected at early infection stage and by using integrated management practices.
- For the diseased trees, apply 20 lit of 1% Bordeaux mixture or 0.2% Carbendizim (2g/lit of water) at the tree basin immediately after the next day of irrigation.
- Initial symptoms of root rot generally appear in the summer season. Apply leaf mulches or agricultural wastes such as paddy husk, groundnut husk, dried leaves, black gram or green gram husk, saw dust to the infected trees at 2-3 inch thickness.
- Immediately after the start of rains (August- September), apply green leaf manures such as neem, Crotalaria juncea, Cassia auriculata, Cissus quadrangularis, Vigna species below the soil in the tree basin. On top of the manure, apply single super phosphate (1kg/tree), mix thoroughly deep into the soil. Green leaf manures helps in increasing the biocontrol agent populations such as Trichoderma in the soil and thereby disease control.
- Apply 10 kg mixture of Trichoderma culture for each tree (mix 1 kg Trichoderma culture + 90 kg FYM + 10 kg neem cake, kept it aside for 4-5 days) at the trunk basins and mix it well. Repeat the same after six months. Application of 5 kg of this mixture every year to the healthy trees prevents root rot.
5. Ganoderma root rot (Ganoderma or Puttagodugu or Puttakokku Tegulu) (Ganoderma lucidum)
The entire plant wilts and dies in extreme cases. The roots become weak and pliable. Numerous brackets like objects are produced at the base of the stem and also in the trunk to some height.
These mushrooms also infect Coconut, Mango, Jackfruit trees. So, collect and destroy the mushrooms on these crops. Continuously watch for the mushrooms, particularly in the rainy season and destroy them. Cut the diseased older trunk portions and apply Bordeaux paste. Apply 1 lit / Sq.m area of carbendazim (1gm / liter of water) or Aureofungin sal (1.5g / 5 liters of water) or Tridemorph (2.5g / liter of water).
6. Twig blight (Colletotrichum gloeosporioides, Botryodiplodia theobromae)
Light brown to dark brown discolouration of leaves. They get defoliated. The naked twigs have profuse black colored fructification on grayish twigs.
Pruning and burning of the affected twigs before the rainy season followed by spraying of 0.1% Carbendazim (10gm in 10 lit of water) or Copper oxychloride 3g / lit of water twice at monthly interval reduces the disease.
7. Powdery mildew (Budida Tegulu) (Acrisporium tingitanium)
White powdery growth is formed on the surface of the leaves.
Spraying of Karathane 0.1% or Wettable Sulphur 0.2% twice at 15 days interval reduces the disease incidence.
8. Felt disease (Septobasidium spp)
Soft felt like leathery fungal growth encircles petiole, leaf base, twigs, branches and fruit stacks. The causal fungus grows over the surface, and it does not penetrate the bark tissues.
Pruning and destruction of diseased twigs before the onset of monsoon. Spraying of Monocrotophos (1.6ml) with Mancozeb (2g) or Captan (2g / lit of water) controls the scale insects and the disease.
9. Pink disease (Pellicularia salmonicolour)
Whitish mycelial growth appears on the infected twigs. Later white or pink pustules appear on the twigs. 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.
Cut-off the diseased twigs, which are drying after the rainy season and destroy them. Apply Bordeaux paste on the cut surface of the twigs.
10. Pre-harvest stem end rot (Gloeosporium limetticola)
Brown colored round spot appears at the stem end of the fruit, and the rotting spreads gradually throughout the fruit. As the disease advances, the color charges from brown to chestnut brown. The fungus spreads up to 2-3 cm in the stem and rots that portion. Some of the affected fruits drop off. Some rot and dry on the tree attached to the fruit stalk.
The infected and dried fruits should be pruned along with the fruit stalks and destroyed. Spray 10g of Carbendazim in 10 lit of water and apply three times at monthly intervals in June, July and August months. Spray should cover thoroughly the leaves and fruits.
11. Greasy spot (Mycospherella citri)
Symptoms include oily, chestnut brown spots or blister-like lesions on an underside of mature leaves. Smaller spots coalesce and become larger. The disease is severe in rainy and winter season. Heavily infected leaves drop off before reaching maturity, and the twigs are defoliated.
Spray Copper oxychloride 30g / 10 lit of water or 25g Zeneb (0.25% in 10 lit of water) twice in June, July at 20 days interval. Spray should cover the lower surface of the leaves thoroughly.
12. Longitudinal bark and wood splitting disease (Botryodiplodia theobromae)
The symptoms first appear as two longitudinal splits on trunk and branches. The splits gradually deepen into inner woody portions of the stem and appear as a canal. The tissue within the splits is dead, and the branches above the split region dry up from top to bottom.
Spray Carbendazim (10g/10 lit of water) twice at 15 days interval when the initial symptoms are observed. Spray should cover the trunk and branches thoroughly. Apply Bordeaux mixture (1lt / 1 sq.m area) the next day after irrigation. Cut and destroy dried up twigs and branches before spray.
Bacterial diseases of Citrus
Canker and Greening are the two main bacterial diseases of citrus.
1.Canker (Gajji or Bobbara Tegulu) (Xanthomonas auxonopodis Pv. Citrii)
Corky out growths develops on the leaves, fruits, and twigs. The disease is serious in acid lime.
- Canker tolerant acid lime variety ‘Balaji’ was developed by Citrus Research Station, Tirupati. The variety is canker, tolerant and high yielding. Farmers can obtain the variety from Citrus Research Station, Tirupati.
- Diseased twigs and branches should be pruned and destroyed before the rainy season.
- Spray Streptocycline (1g) + Copper oxychloride (30g) in 10lt of water, twice on young flushes in rainy season at 20 days interval.
- Control of leaf miner in acid lime orchards can reduce canker.
- To prevent canker on fruits, spray the above chemicals on small fruits twice at monthly interval. Spray should cover entire fruits.
- If canker is present on the trunk and main branches, scrap that portion and apply Bordeaux paste on the effected area.
2. Greening disease (Leptobacterium asiaticum)
Leaf patterns include chlorosis resembling zinc deficiency (sometimes dotted with green islands), and yellowing of veins. Reduction in fruit size and die-back of twigs are also noticed. The pathogen is spread by use of infected bud wood and by the citrus psylla (Diaphornia citri)
- Selection of certified disease-free budlings.
- Application of Dimethoate to control psylla (as in the case of psylla control).
Viral diseases of Citrus
1. Tristeza disease (Quick decline or die-back)
The decay of roots, die-back of twigs, diminished fruit-set, vein-clearing in leaves and stem pittings are symptoms of tristeza virus. The disease is transmitted by budding and by certain aphids including (Toxoptera citricida, Aphis gossypi, and A.craccivora)
The disease is distributed throughout the world. It affects mostly acid lime orchards. Symptoms are very clear in lime trees. Tristeza affected trees look chloratic and sickly in the early stages. Gradually the leaves drop, and the defoliated twigs show die-back. The declining trees die gradually, but sometimes apparently healthy trees die suddenly. Diseased trees usually blossom heavily. They bear small sized fruits. As the fruits develop, the tree wilts partly or completely. Vein clearing in young leaves of acid lime, which is seen intermittently when viewed against light is a characteristic symptom.
In sweet orange, the specific symptoms of tristiza are stem pitting on the rootstocks such as Jambhiri. It is fine pitting of inner face of bark in the portion of the trunk below the bud union. The disease primarily spreads through the use of diseased bud wood by the nurserymen. Under field conditions, the disease is transmitted by the aphid, Taxoptera citricida.
Tolerant rootstocks such as sweet orange, trifoliate orange, Cleopatra mandarin and Rangpurlime have to be used. Budded plants free from the virus are to be planted.
2. Mosaic disease
Symptoms appear on leaves and fruits. Affected leaves show irregular yellow or light green patches alternating with normal green areas. Reduction in leaf size and leaf drop is observed. Fruits show depressed yellow patches and elevated green areas. Reduction in fruit size is common. The disease is transmitted through infected bud wood.
3. Bud-union crease disease
In the diseased plants stem looks swollen near the bud joint. When the bark near the bud joint is cut open, the honey colored mark is visible on the wood. When the disease is severe, and the mark is visible on the stem, transport of food material is not possible, and the roots may die. The disease is observed on sweet orange plants grafted on Jambhiri root stocks but not on Rangpurlime root stocks (in Ananthapur district).
4. Yellow corky vein disease
The disease occurs in sweet orange and acid lime trees. The disease initially produces yellowing of midrib and lateral veins. In advanced stages, mid-rib becomes corky on the lower surface, and the leaves finally curl. The disease is transmitted through infected bud wood.
Control measures for viral diseases
There are no effective practical treatments to cure citrus trees once they are infected with viral diseases such as tristeza, mosaic, bud union crease, yellow corky vein, etc., Propagation of the plants should not be done from diseased trees. Sometimes identification of viral diseases in the plants is difficult. So, farmers should buy the bud sticks from Citrus Research Station, Tirupati. At the center, the bud sticks are supplied after indexing the plants for viral diseases. When the farmers use such indexed bud sticks and graft them on Rangpurlime rootstocks, they can minimize the viral diseases to the maximum extent.
5. Lime Bark Eruptions (Nimma Beradu Pokkulu)
Yellowish brown corky bark eruptions develop around the branches. This disease has become serious in acid lime plantations.
In the early stages, light scraping of such portions and application of Bordeaux paste can relieve the incidence.
“CITRUS(Citrus Spp) – drysrhu.” Dr. Y S R Horticulture University. N.p., n.d. Web. 09 May. 2017 <http://www.drysrhu.edu.in/crops/citrus.html>.
CITRUS(Citrus Spp) – drysrhu. (n.d.). Retrieved from http://www.drysrhu.edu.in/crops/citrus.html
- Dr. Y S R Horticulture University, Andhra Pradesh.