Healthy Plant (Darjeeling Mandarin)Fruit crops play an important role in the life of farmers of North Eastern hill regions. Fruit crops make hill agriculture vibrant and potentiate the economic condition of the farmers of this region. In Darjeeling region of West Bengal and Sikkim, cultivation of fruit crops mainly Darjeeling Mandarin is main source of livelihood for the farmers.

In India, every year a huge loss to citrus production occurs due to damage caused by insect pests, diseases and off course physiological disorders. All these factors together cause a great damage to citrus crops; and growers as well as consumers are disadvantaged with it.  

A. Disease Pests and their Management:

The diseases are caused by fungi, bacteria, virus, virus like pathogens, etc. They cause severe damage to the mandarin orange cultivation. The major diseases affecting citrus crops in Darjeeling and Sikkim regions are as follows:

1. Gummosis disease (Causal organism: Phytophthora palmivora, P. citrophthora, P. nicotianae var. parasitica):

The characteristic symptom of the disease is exudation of gum from bark of the tree trunk. The leaves of affected plants, turn yellow and show blight symptoms. The bark shows conspicuous brown staining along with hardened masses of gum on the surface. The bark cracks open and in the later stages dry up and fall off, exposing the wood for secondary infection by other microorganisms. In severe cases, the bark is destroyed by complete rotting, the trunk exhibits a characteristic girdling and the tree eventually dies. Prior to death, the plant usually blossoms heavily and dies before the fruits mature. In such cases, the disease is called collar rot or foot rot.

Management:

  • Preventive measures like selection of site with proper drainage, avoiding direct contact of irrigation water with the trunk by adopting double ring irrigation method; and use of resistant rootstock such as sour orange (Citrus aurantium), trifoliate orange and Rangpur lime are effective against the disease.
  • The budding should be done on rootstock at 35–40 cm height.
  • Injuries to the plants should be avoided.
  • After scraping the diseased parts with a sharp knife, the cut portions should be protected with Ridomil MZ-68 paste (20g in 1 L of linseed oil) or copper fungicides paste followed by 3–5 spraying with 0.3% Copper oxychloride or 0.2% Ridomil MZ at 15 days interval reduces disease spread effectively.
  • Soil drenching with 0.2% Metalaxyl MZ-72 + 0.5% Trichoderma viride commercial formulation is also effective in managing the disease.
  • The trunk should be painted with Bordeaux paste up to 50-75 cm height from the ground level at least once a year.

Powdery Mildew Disease2. Powdery mildew (Causal organism: Acrosporium tingitaninum):

The disease appears as white, cottony or powdery growth on all aerial parts of the affected plant. The affected leaves show yellowing and crinkling; and they have distorted margins. The cottony growth becomes black and severely affected leaves dry up or drops off prematurely. The symptoms are more severe on the upper surface of the leaves, but are also present on the lower surface. In severe infections, young fruits also get covered by mildew growth and drop off prematurely. Consequently the yield is reduced considerably.

Management:

  • The affected parts should be removed and destroyed carefully.
  • Immediately, after the cottony growth is observed spraying of 0.3% Sulfex or 0.2% Carbendazim, three times at 15-20 days interval effectively controls the disease.
  • Sulphur dusting (25kg/hectare) in the morning hours controls the disease effectively.
  • Sprays with fungicides like 0.1% Calixin (Tridemorph) or Thiovit @ 2.5 g/ L water or Karathane @ 2–3 ml or 0.25% wettable sulpur or 0.1% Dinocap gives satisfactory and prolonged control of the disease.
  • The spraying should be repeated, if necessary at 10–15 days interval.

Fruits of Darjeeling Mandarin showing Canker Disease3. Citrus canker disease (Causal organism: Xanthomonas axonopodis pv. citri)

It is most serious bacterial disease of citrus crops during rainy season and it can cause severe losses. The disease appears on leaves, twigs, petioles, branches, fruits, fruit-stalks and thorns. Initially, the symptoms on leaves appear as yellowish, small, raised translucent spots/ lesions, which gradually enlarge 2-4 mm in diameter and appear as raised rough brownish pustules. Later, the epidermis over the spot ruptures to expose a crater-like spongy, tan-coloured tissue. A characteristic yellow halo surrounds the spot till it becomes old. Old lesions are corky, irregular in shape and brown in colour. Severely affected leaves drop off prematurely. On the twigs the lesions appear water-soaked and dark green first and later turn brown. The pustules on twigs are corky, but without crater-like depression. In severe cases, the twigs dry up. The infection on fruit appears as water-soaked lesions, similar to those on leaves except for the yellow halo. In the advanced stage these lesions show crater-like depressions. The fruit lesions become rough and corky and sometimes cause cracks and fissures of the skin. Cankered fruits drop off prematurely. Canker lesions are confined to the rind only and do not penetrate into the flesh of the fruit. The marketability of the infected fruits is seriously affected.

Leaves of Darjeeling Mandarin showing Canker DiseaseManagement:

  • The disease incidence can be reduced at farmers' field by pruning all the canker affected twigs before monsoon and burning them.
  • The pruned branches or other plant's parts should be protected by paste of copper fungicides (e.g. Blitox–50) to prevent the further spread of this disease.
  • After pruning 2–3 spraying of copper fungicides e.g. 0.3% Blitox–50 along with streptomycin sulphate 500-1000 ppm (0.5–1.5g per L of water) after onset of the monsoon is quite effective to check this disease. Spraying the crop with 0.2% Mancozeb is also helpful in reducing the disease incidence.   
  • Spray of Phytomycin antibiotic @1500 ppm in combination with 0.3% Copper oxychloride also helps in the management of the disease in the beginning of monsoon.

Citrus Tristeza Disease4. Citrus Tristeza Disease

The disease is caused by Citrus Tristiza Virus (CTV). This disease is primarily spread through the use of diseased bud-wood. Citrus aphid (Toxoptera citricida), vector of the disease transmits this virus in the healthy orchards. The symptoms begin with the dieback of small branches and twigs, yellowing of leaves and heavy bearing of small fruits. As the disease advances, severe chlorosis and mottling can be seen. The roots of the affected plants start rotting and plants die. After 7-8 years, the branches of the affected plant dry up severely and the plants wilt 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. This disease may present independently or along with citrus greening disease. CTV infected diseased young trees tend to flower a year or two earlier than the healthy plants and their fruits are small in size and develop colour early. In acid lime, vein fleckings or clearing and stem pittings are observed. Affected acid lime trees decline gradually. Bark splitting of lime twigs has also been observed. Sweet orange varieties are symptom-less carriers but their susceptible root stock of budlings show stem pits. Mandarin oranges grown from seed, show the disease symptoms like leaf fall, twig die-back, stem pitting, etc.

Management:

  • Healthy and certified bud-wood should be used.
  • Proper tillage practices, adequate drainage and improved soil fertility help to avoid the disease incidence.
  • Resistant root stock such as trifoliate orange, Rangpur lime and Cleopatra mandarin should be used for vegetative propagation.
  • Nucellar seedlings remain free from Citrus Tristeza Virus. It can be used as effective means to avoid this disease.
  • Aphids, which are vector of Citrus Tristeza Virus should be destroyed by spraying the crop with Diamethoate or Monocrotophos @ 1.5 ml/L of water.
  • Spraying the crop with Malathion @ 2.5 ml/L of water or Imidachloprid @ 0.25ml/L of water or Thiamethoxam @ 0.25 g/L of water or Acetamiprid @ 0.3 g/L of water may be used for effective control. Besides these NSKE @ 3-5 ml/L of water may also be used for satisfactory control of the citrus aphids.

Citrus Greening Disease5. Citrus Greening disease:

This disease is wide-spread and so acute in India that there is a danger of destruction of Indian origin citrus species. The causal agent of this disease is phloem limited bacterium. This disease is spread through grafting and citrus psylla (Diaphorina citri). In this disease, varied chlorotic patterns on leaves are noticed. Veins of affected leaves turn yellow, leaves remain undersized and foliage become leathery and turns dull green. Heavy leaf fall occurs with the onset of summer. Affected trees are stunted with pronounced leaf and fruit drop. Some branches on affected tree, exhibit severe twig dieback symptoms, whereas the others remain apparently normal. The fruits of affected trees remain mostly green even on maturity and if directly exposed to sun they show a conspicuous yellow patch on the rind surface. Diseased fruits are valueless owing to small size, distortion, low juice and insipid taste. Sweet orange, grapefruit and kagzi lime are indicator of this disease.

Management:

  • The bud wood should be free from the greening disease preferably from mature seedling trees duly indexed for the disease.
  • Spraying the crop with Fenvalerate @ 1 ml/L of water or Metasystox @ 2 ml/L of water or Profenophos @ 3 ml/L of water or Thiamethoxam @ 0.2 g/L of water gives effective control of citrus psyllids.
  • Temporary suppression of the disease is possible by injecting the infected plants with Tetracycline 500 ppm or spraying the crop with Bavistin @ 500ppm + Ladermycin @ 500 ppm in 1 litre of water.  

6. Citrus scab (Causal organism: Eisinoe fawcetti):

Scab is one of the major diseases in the hilly tracts where low temperature and high humidity prevail. It is common in Darjeeling hills, Sikkim, Assam and other North Eastern States. The disease attacks on leaves, twigs and fruits. Small, raised, corky lesions appear usually on the underside on the leaves. The affected leaves often become distorted, wrinkled, stunted and de-shaped. The opposite surface corresponding to the warty growth shows a circular depression with a pink to red centre. The twig infection also results in similar lesion and the affected twigs are ultimately killed. On the fruits, scabby or corky lesions develop and they soon coalesce affecting larger area on the fruits. The surface becomes rough and distorted and fruit may drop off prematurely. Humidity and rainfall play a very important role in the development of scab.

Management:

  • The diseased leaves, twigs and fruits should be collected and destroyed.
  • After pruning and destruction of the diseased leaves, twigs, branches and fruits; spraying the crop with 0.3% Copper oxychloride or 0.2% Carbendazim are helpful in controlling the disease.

7. Anthracnose or wither tip/die back (Causal organism: Colletotrichum gloeosporioides):

In this disease leaves, young shoots and tender fruits are often attacked. Affected leaves turn yellow, show necrotic patches with distortions. The disease severely affects branches, which starts to wither from the tip downwards. The drying back gradually progresses downward with leaves turning yellow, withering and drooping and gum formation on the stem. Dead pans of the twigs assume silvery grey appearance. Fruit drop occurs in the severe stages.

Management:

  • Pruning of diseased twigs and its protection with copper fungicide (e.g. Blitox–50) paste is quite effective in checking this disease.
  • Spraying of Blitox–50 (2.5g/L of water) or Mancozeb (2.0 g/L of water) is very effective against this disease. Spray of 0.2% Zineb or 0.2% Captan also helps to minimize the disease.
  • Proper irrigation and need based use of fertilizers especially nitrogenous fertilizer helps to avoid the disease.

B. Insect Pests and their Management       

Major insect pests problematic to mandarin orange in North Eastern Hill regions of Darjeeling and Sikkim are leaf miner, citrus psylla, citrus fruit sucking moth, citrus stem borer etc. These major insects and their management are as following-

Citrus Leaf Miner1. Citrus leaf miner (Phyllocnistis citrella):

It is a common pest of citrus crops in India. The adult of this pest is a minute silvery white or greyish moth. Usually leaf miner is more active during their growth period i.e., in spring and rainy seasons. Tender leaves are attacked and leaf miner larvae feed on the epidermis, producing silver coloured serpentine mines, generally on the lower surface. Often the tiny caterpillars/grubs are found in them. Larvae also attack the tender branches where they mine under the epidermis. Both young and old trees are affected but the damage to young plants is more serious. A heavy attack may lead severe defoliation. The infested trees are devitalized and look sickly. Leaves which are mined also serve as loci of infection for citrus canker disease.

Management:

  • Chipping and destruction of mined leaves in the primary stage reduces insect infestation.
  • Timely sprays of Dimethoate @ 2ml/L of water or Profenofos @ 2-3ml/L of water or Thiamethoxam @ 0.2 g/L of water provide satisfactory control.
  • Regular monitoring plays vital role in the management of the insect.  

2. Citrus psylla (Diaphorina citri):

The damage is mainly caused by the nymphs of citrus psylla, which suck the sap from the leaves, young shoots, buds, flowers and tender branches; flowers shed in large numbers. The infested leaves curl and fall off prematurely. In severe cases, they may weaken the trees. The fruits remain small and of poor quality. The twigs and sometimes the entire tree may decline. The nymphs secrete honeydew like substance on which sooty mould fungus develops. The sooty mould fungus does not allow the plants to grow vigourously by affecting its photosynthesis, adversely. Citrus psylla is also reported to be a vector of citrus greening bacterium and indirectly damages the plants more.

Management:

  • Diseased plant parts should be pruned and destroyed by burning them.
  • Spraying the trees with resin compound, crude oil emulsion with sulphur gives satisfactory control.
  • Spraying of Fenvalerate @ 1 ml/L of water or Metasystox @ 2 ml/L of water or Phosalone @ 1.5–2.0 ml/L of water or Profenofos @ 3 ml/L of water or Thiamethoxam @ 0.2 g/L of water also effectively reduce population of the insect.
  • Hoverflies, lady bird beetles and lacewing insects are reported as predators of this pest. The population of these natural enemies should be promoted for effective, eco-friendly management of citrus psylla insect.

Citrus Fruit Flies3. Citrus Fruit flies (Bactrocera dorsalis):

Sometimes, these are very serious pests in Darjeeling and Sikkim hills, especially during the monsoon season. The fruit fly looks almost similar to the housefly, and can be distinguished from the common housefly by its triangular shaped abdomen and spotted wings. The fruit flies lay eggs under the ripening fruit rind by means of its piercing ovipositor. The eggs hatch out within few days and the maggots start feeding inside fruits. These maggots spoil the taste and market value of these fruits. The damage occurs more, if the fruits are retained late on the trees after maturity. The affected fruits can be easily distinguished by the presence of a rotten, round patch at the place where it was pierced by the flies. Affected fruits fall on the ground. The maggot pupates in the soil and emerges as flies after 7-10 days.

Management:

  • Fruit flies are very difficult to be controlled. Infested fruits should be collected and burnt so that the maggots are killed. The maggots must not be allowed to emerge out from the fruits and pupate in the soil.
  • Raking or ploughing the soil to destroy pupae is beneficial and application of Carbaryl dust to soil underneath the tree canopy kills the pupating maggots and pupae, and help in reducing infestation level.
  • Bagging of the still hard and green fruits with craft paper bags also avoids damage.
  • Installation of methyl eugenol trap is found quite effective in managing the population.
  • Citrus fruit flies can be effectively controlled by poison baiting with 20 ml Malathion or 50 ml Diazinon mixed with 200 g gur (jaggery) in 2 liters of water. This mixture is filled in plastic tub and 60 watt bulb is fixed over it to attract moth during night time. Moths will be attracted towards light trap. After falling in this mixture moths get killed. The fallen fruits should be buried in a pit and cover with soil every day.

4. Lemon butterfly (Papilio demoleus):

Caterpillars of the butterfly are commonly seen feeding voraciously on the leaves of citrus plants. They are more damaging to the young plants, as compared to older trees. Considerable damage is caused to citrus plants by this insect in the nursery and young orchards. In severe cases, they completely defoliate the plants.

The caterpillars are cylindrical, dark brown with irregular whitish markings on dorsal side of the abdomen; and may assume size up to two inches in length. Larvae resemble bird's drooping to escape from predators. The larvae eat the tender leaves and develop into thick green coloured one. Larvae are voracious eaters of the leaves and can devour entire foliage. This can be a serious pest in nursery also. These insects are more damaging in the months of March–May and again in August–October.

Management:

  • This pest can be picked up and destroyed mechanically in larval (caterpillar) and pupal stages when their population is low or when the attack has just started.
  • Spraying the crop with Chlorpyrifos @ 3 ml/ L water or Deltamethrin/ Fenvalerate @ 1ml/ L or Carbaryl @ 2.5 g/L of water is also effective against this pest.
  • Spraying the crop with NSKE @ 3-5 ml/L of water also reduces the insect infestation effectively.

5. Fruit sucking moths (Otheris fullonica, Achaea janata L.):

These moths are grey in colour and have orange colour wings. The adult moths fly at night and cause damage by sucking the juice from the ripe fruit by drilling holes in it. The green fruits are also not spared from attack. As a result, the area around the puncture caused by the proboscis becomes soft and fungal and bacterial infection take place there. The affected fruits gradually begin to rot, become worthless and fall down immediately or within few days.  Fruit sucking moths attack during the rainy season.

Management:

  • The population of this insect can be minimized by avoiding the rainy season crop.
  • This pest has alternate wild hosts, hence the elimination of larval host plants help in protecting the orchards.
  • Capturing the moths by hand nets, baited traps (with or without poison) smoking and prompt burning of fallen and decaying fruits and early harvesting or covering individual fruits when half ripe with paper bags help in managing this insect.
  • Fruit sucking moth can be effectively controlled by poison baiting with 20 ml Malathion or 50 ml Diazinon mixed with 200 g gur (jaggery) in 2 liters of water. This mixture is filled in plastic tub and 60 watt bulb is fixed over it to attract moth during night time. Moths will be attracted towards light trap. After falling in this mixture moths get killed.
  • Since, the moths are attracted to light; placing a strong light over water mixed with kerosene reduced their population.
  • Spraying the fruits with NSKE @ 3-5 ml/L of water or Rynaxypyr 0.33 ml/L of water or Flubendiamide 0.25 ml/ L of water also gives satisfactory control.

Citrus Aphid6. Aphids (Toxoptera citricida):

Aphids are tiny green or black sucking insects found adhering in clusters to the underside of young citrus leaves and new shoots. In India, brown citrus aphids and black citrus aphid are more prevalent and cause major damage. Aphids are more active during December-March. The affected leaves curl, deform and growth of the young shoots is checked. Sometimes, blossoms and newly set fruits are also attacked. They secrete a honey dew like substance on which sooty-mould grows, which impairs the normal functioning of leaves. Citrus aphids are more important with respect to the spread of Citrus Tristeza Virus in citrus orchards. Brown citrus aphid is the main vector of this dreadful virus.

Management:

  • Generally, aphids are kept in check by predators such as lady bird beetle or other natural enemies, which feed on them. If sufficient numbers of such beetles are absent, aphid attack may become severe. Under such conditions, control measures become essential, and it must be taken up before leaves begin curling.
  • For spraying Malathion 2.5 ml/L of water or Imidacloprid @ 0.25–0.50ml/L of water or Thiamethoxam @ 0.25 g/L of water or Acetamiprid @ 0.3 g/L of water may be used for effective management. Besides these NSKE @ 3-5 ml/L of water may also be used.

7. Shoot borer/Trunk borer:

Citrus Shoot Borer Insect 

Citrus Shoot Borer Insect

It attacks more vigourously in September-October. Fresh hatched larvae bore into the young twigs and feed on the soft tissues. This insect feed upon bark of citrus tree during day hours and hide itself in holes bored into the shoots/ twigs in the night. Affected twigs break and dry. Severely affected plants lose its vigour and look sickly.   

The trunk borer insect is very serious pest of citrus plants. The grub of the trunk borer insect bores the tree trunk near ground level horizontally up to the pith and then tunnels vertically and again horizontally for exit. The attacked tree gradually dries up with leaves turning yellow and drop off prematurely.

Citrus Shoot Borer Insect  

Management:

  • The affected branches/shoots should be pruned 4-5 cm below the dried portions and destroyed.
  • Do not cause any physical injury to the trunk or main branches.
  • After pruning spraying the crop with Monocrotophos 36 WSC @ 1 ml/L of water or Quinalphos 25 EC @ 1.5 ml/L of water or Carbaryl 50 WP @ 2 g/ L of water reduces the insect infestation considerably.
  • Inject kerosene oil/ petrol and plug the hole with wet clay.
  • Swabbing of tunnel and plugging the fresh holes either with Dichlorvos (0.5%) or Monocrotophos (5 ml/20 ml of water) kills the trunk borer grubs effectively.

Citrus Decline C. Citrus decline complex:

Citrus decline, also often referred as citrus "die back" is not a specific disease but is a symptomatic expression of many disorders in the plant. The term die back actually describes the continuous dying of twigs downward. The earliest symptom of decline is the complete suppression of normal seasonal flushes. Affected trees blossom heavily, produce a large crop and collapse suddenly. 

Symptoms of decline may vary with the cause of the malady. All the citrus species and varieties are susceptible, but the sweet and mandarin oranges are worst affected by this problem. Budded, as well as, seedling trees suffer from this malady. In early stages, symptoms are restricted to a few limbs, but eventually the whole tree is involved. Trees show sparse mottling leaves, stunted growth, and sickly appearance. Midrib and lateral veins of old, mature leaves turn yellow with interveinal areas along the veins showing diffuse yellowing. Leaves may turn yellow and are shed with the onset of summer or autumn and the die-back of twigs starts. The die-back symptoms may reach down to the main trunk. The entire tree bears short twigs carrying narrow small leaves on their lower portion. Subsequent secondary growth consists of short, upright small, weak shoots showing a variety of discolouration of leaves. Often these leaves have green veins of green blotches. Occasionally, small, circular, green spots appear on yellow tissue on leaves. The die-back of weak shoots continues. There is excessive flowering, but the fruits are not carried to maturity. The fruits show distinct sun-blotching. The feeder root system becomes depleted; roots turn black and sometimes are covered with rotting bark. Either only a few trees or entire orchard may be affected. Some-times citrus tree may suddenly wilt and die within a day or two.

Factors responsible for citrus decline:

A number of factors are responsible for the decline of citrus trees. Some important factors are discussed below –

  1. Nutritional factors: Plant nutrition is among the most important factors responsible for citrus decline. Citrus decline of oranges in hilly regions is due to the deficiencies of several mineral elements including zinc, manganese and boron.
  2. Rootstock factors: Rough lemon is widely used as rootstock in India and some other countries. In many instances, failure of citrus trees may be attributed to incompatibility between stock and scion. Susceptibility of rootstocks to root rots, salinity, water logging, cold, virus etc. also leads to citrus decline.
  3. Orchard management factors: Mismanagement and negligence in orchard practices can lead to decline of citrus trees. Excessive intercropping, faulty methods used, excess or no manuring, improper irrigation, are some of the common causes leading to citrus decline. Bad drainage causes poor aeration due to poor aeration plant root developments arrested, leading to less absorption of the nutrients and ultimately to the decline of the top.
  4. Insect pests: Several insects attack citrus and cause damage by direct feeding and by acting as vectors for viruses and other pathogens. Citrus leaf minor is a very serious pest of citrus foliage. White flies reduce plant vigour by sucking plant sap. The nymphs and adults of citrus psylla suck sap from leaves and tender shoots causing curling and defoliation and death of shoots. Thus, there are several insects which by direct feeding on leaves, flowers, fruits, etc. devitalize the citrus plants and ultimately lead to decline.
  5. Nematodes: Nematodes cause damage to citrus trees by feeding on their roots and they can cause "slaw decline" and "spreading decline" diseases in citrus. Therefore, severe nematodes infestation leads lo citrus decline.
  6. Pathogenic diseases and their agents: Many fungal diseases of citrus like gummosis, foot rot, Ganoderma dry root rot, powdery mildew, anthracnose, canker, scab disease etc. reduce the vitality of citrus trees and lead to the decline. Viruses are the most potent factors leading to citrus decline. Citrus Tristeza, psorosis, exocortis, etc viral diseases contribute to citrus decline. Citrus Tristeza Virus is the main contributor of decline. Virus infected trees become stunted and show die-back of twigs and branches. The Productivity is substantially reduced. Another important contributing factor is greening disease. It is reported from all over the country to cause citrus decline.

Management practices:

Control depends on the cause of decline. Accurate diagnosis is very essential for the management of this problem.

  • It is necessary that present rootstocks such as rough lemon etc. are replaced by those of Rangpur lime, Cleopatra mandarin, sweet orange and trifoliate varieties which are resistant to Tristeza virus. Plant should be grown from virus free source viz., bud wood from nucellar seedling plantations, because these seedlings are free from viral infection.
  • Drainage and weed management should be good. Proper nutrient supply to the orchard must be ensured. Timely management of diseases and insect-pests should be done. Soils with very high pH should be avoided for citrus plantation.  
  • Infected parts should be pruned and after pruning should be sprayed with Copper oxychloride @ 3.0 g/L of water or Mancozeb @ 2.0 g/L of water at 15-20 days interval.
  • The root region of plants should supplied with 2.5 kg Vermicompost+2.0 kg Neem cake +100 g Reagent+ 50 g Bavistin + 50 g mixture of micronutrients per tree twice in monsoon.
  • Micronutrient deficiency should be timely corrected by spraying micronutrients’ solutions twice in year during February-April.

SUMMARY

Citrus especially Darjeeling mandarin is one of the most important fruit crops of Darjeeling and Sikkim hills of North Eastern region of Himalaya. It plays an important role in providing energy, food and certain vitamins. Besides, it is a good source of income for the growers especially in these challenged areas. Off-course several devastating diseases such as gummosis, powdery mildew, canker disease, citrus tristeza, citrus greening etc. and many insects pests attack on the citrus crops but timely use of management tools for their effective management in these regions can really help to uplift the farmers’ economic condition to a greatest extent.

 

Table 1: Recommended fungicides & pesticides for the management of diseases and insect pests in Mandarin orange**

Target Disease / Pest

Fungicides/ Pesticides

Dose (g/L or ml/L)

of most common formulation*

Method of application

Gummosis disease

Ridomil MZ

2.0

Foliar spraying

Copper oxychloride

3.0

Foliar spraying

Ridomil MZ

20

Apply as paste

Powdery mildew

Sulfex

3.0

Foliar spraying

Karathane

2.0 - 3.0

Foliar spraying

Citrus canker

Blitox–50 + Streptomycin sulphate

3.0 + 0.5 – 1.5

Foliar spraying

Mancozeb

2.0

Foliar spraying

Citrus Tristeza Disease 

Diamethoate

1.5

Foliar spraying

Malathion

2.5

Foliar spraying

Citrus Greening disease

Fenvalerate

1.0

Foliar spraying

Profenophos

 3.0

Foliar spraying

Citrus scab

Copper oxychloride

3.0

Foliar spraying

Carbendazim

2.0

Foliar spraying

Anthracnose/die back

Blitox–50

2.5

Foliar spraying

Mancozeb

2.0

Foliar spraying

Citrus leaf miner

Dimethoate

2.0

Foliar spraying

profenofos

2.0-3.0

Foliar spraying

Citrus psylla

Fenvalerate

1.0  

Foliar spraying

Phosalone

1.5 – 2.0

Foliar spraying

Thiamethoxam

0.2

Foliar spraying

Citrus Fruit flies

Carbaryl

-

Dusting

Lemon butterfly

Chlorpyrifos

3.0

Foliar spraying

Carbaryl

2.5

Foliar spraying

Fruit sucking moths

Rynaxypyr

0.33

Foliar spraying

Flubendiamide

0.25

Foliar spraying

Citrus Aphids

Malathion

2.5

Foliar spraying

Imidacloprid

0.25–0.50

Foliar spraying

Shoot borer /trunk borer

Quinalphos

 1.5

Foliar spraying

Carbaryl

2.0

Foliar spraying

Dichlorvos

5.0

Swabbing of insect tunnels

*Indicative dose given for convenience of famers **Details available in the article


Authors:

Ravindra Kumar*, Amalendu Ghosh, Amrita Das and Ramu Meena

ICAR-Indian Agricultural Research Institute, Regional Station, Kalimpong –734301 (W.B.)

* Present Address: ICAR-Indian Agricultural Research Institute, Regional Station, Karnal – 132001 (Haryana)

*Email- This email address is being protected from spambots. You need JavaScript enabled to view it.