🌸 Citrus — Nutrient Deficiencies,

This lesson details citrus nutrient deficiencies, common disorders, and integrated management practices for healthy orchards.

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PHYSIOLOGICAL DISORDERS, PESTS AND DISEASES AND

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INTEGRATED MANAGEMENT PRACTICES

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CITRUS

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Fruit cracking

• It is due to sudden changes in temperature and also due to moisture stress condition.

• Cracking of fruits may be radial or transverse.

• Secondary infection is also possible due to Aspergillus, Fusarium or Alternaria

Management

• Apply light irrigation at frequent intervals.

• Application of potassium during fruit development.

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Granulation

• The juice vesicles become hard, enlarged and turn opaque grayish in colour.

• The density of pulp is increased, juice contains increased minerals (Calcium, sodium,

potassium) and decreased carbohydrate and organic acid.

• It results in lignification of juice cells that leads to formation of sclerenchyma

• High humidity and fluctuation in temperature are the major factors.

• Young trees are more prone to granulation than older trees.

• Application of more nitrogen, excess irrigation, large size of fruits, rootstocks are also a

cause.

• Mandarins on jattikhatti rootstock are more susceptible than sweet orange .

Management

• Avoid excess moisture

• Spray lime @ 20kg in 450 l of water.

• Spray zinc (0.5%) and copper (0.5%).

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Sunburn or sunscald

• The portion that is exposed to sun develops yellow patches which turn brown and

become hard.

• The inner portion becomes dessicated and discoloured.

• Affected fruits are malformed and have low juice content.

• Severely affected fruits drop off and leaves turn brown.

Management

• Spraying lime solution @ 20g//l before summer.

• Regulation of irrigation to reduce the temperature.

• Mulching the tree basins.

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Citrus Decline

• Also known as citrus dieback.

• Growth becomes stunted, mottling of leaves, turn yellow and are shed.

• There is excess flowering and poor fruit set.

• Affected fruits are subjected sun blotching.

• Presence of calcium carbonate or clay is harmful and leads to decline.

• Incompatibility of rootstock and scion, salinity, water logging and mismanagement of

citrus orchard are causes to citrus decline.

Management

• Provide proper drainage

• Proper management of the orchard

• Use of resistant rootstocks and disease free bud wood.

ACID LIME

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Plant protection

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Leaf mine

2 ml/l dimethoate + neem oil 3%

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Leaf caterpillar

Endosulfan – 2 ml/l when infestation is moderate to severe.

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Sucking pest

White fly : Spray quinalphos – 2 ml/lit

Nematodes : Carbofuran – 75 g/tree

P. fluroscens – 20 g

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Diseases

Twig blight: Dried twigs are pruned and sprayed with 0.3% Cu oxy chloride.

Scab: Spray 1% BM

Tristeza virus : Remove the infected trees and destroy. Spray monocrotophos - @ 1ml/lit to

control the aphids which spread the disease. Use pre immunized acid lime seedling for planting.

Harvest: Starts bearing from 3 [rd] year after planting.

Though harvested throughout the year, the main crop is harvested during different

periods in different parts of the country. The average yield is 20-25 kg/tree/year.

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Post harvest treatment

Treating the fruits with 4% wax emulsion followed by pre-packing in 200 guage

polythene bags with 1% ventilation improves the shelf life for more than 10 days. Limes can be

stored at 18°C. At HC & RI, PKM a low cost storage tank has been developed with double layer

brickwork, the interspace filled with sand which is kept wet by periodical watering.

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Summary Cheat Sheet

Topic	Key Point
Deficiency symptoms	Zinc, iron, manganese, and boron deficiencies show distinct foliar and fruit signs.
Physiological disorders	Cracking, granulation, and decline are linked with stress and nutrition imbalance.
Corrective approach	Foliar nutrient sprays and improved water management help symptom recovery.
Pest-disease interface	Orchard stress can intensify pest and disease incidence.
Post-harvest support	Low-cost storage structures help reduce citrus losses after harvest.

References

2 sources • [1] [2]

[1]

Class notes: HORT 181 - Citrus nutrient deficiencies and disorders

[2]

Citrus nutrient correction and storage guidance (as cited in lesson text)