🥭Fruit & Plantation Crop Diseases — Pathogens, Symptoms, and Management

From Field to Lab — Protecting India’s Orchards and Plantations

Walk through a mango orchard in April and you might see white powdery patches covering the panicles — that is powdery mildew, caused by Oidium mangiferae, which can wipe out an entire season’s fruit if left unchecked. In a citrus grove, trees with yellowing leaves and gum oozing from the trunk are suffering from Phytophthora gummosis. A banana plantation where plants topple over in mild wind is likely battling the burrowing nematode (Radopholus similis). And the famous coffee rust — introduced from Sri Lanka in 1870 — continues to threaten coffee production across southern India.

Fruit and plantation crops represent long-term investments, often taking years to reach bearing age. A single disease outbreak can destroy decades of effort. Understanding the pathogens, recognising symptoms early, and applying the right management is critical.

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Mango Diseases

1. Anthracnose — Colletotrichum gloeosporioides

Symptoms:

• Disease appears on young leaves, stems, inflorescence and fruits
• Black necrotic areas develop on twigs from the tip downwards, causing dieback
• In humid weather, minute black dots develop on floral organs
• Infected flower-parts shed, resulting in partial or complete deblossoming

Management:

• Prune and destroy infected twigs
• Spray Carbendazim (0.1%) or Copper oxychloride (0.25%) at flowering

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2. Powdery Mildew — Oidium mangiferae (Acrosporum mangiferae)

Symptoms:

• One of the most serious diseases of mango affecting almost all varieties
• Characteristic white superficial powdery fungal growth on leaves, panicle stalks, flowers and young fruits
• Affected flowers and fruits drop pre-maturely, reducing crop load significantly
• Rains or mists with cooler nights during flowering favour disease spread

Management:

• Dusting with fine sulphur (250-300 mesh) at 0.5 kg/tree soon after flowering
• Second application 15 days later OR spray with Wettable sulphur (0.2%), Carbendazim (0.1%), Tridemorph (0.1%), or Karathane (0.1%)

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3. Mango Malformation — Fusarium moliliforme var. subglutinans

Vector: Bud mite (Aceria mangiferae)

Symptoms:

• Three types: bunchy top phase, floral malformation, and vegetative malformation
• Bunchy top (BT) appears on young plants in nursery beds at 4-5 months old
• Vegetative malformation: Short internodes forming bunches of various sizes at the top of seedling — gives a bunchy top appearance
• Floral malformation (MF): Variation in panicle formation; malformed heads dry up as black masses and persist on the tree

Management:

• Spray 100-200 ppm NAA during October to reduce incidence
• Remove and destroy malformed panicles and vegetative shoots

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4. Sooty Mould — Capnodium mangiferae

Symptoms:

• Black encrustation forms on leaf surface, affecting photosynthesis
• The fungus grows on sugary substances (honeydew) secreted by jassids, aphids and scale insects

Management:

• Control insects and sooty moulds simultaneously
• Spray systemic insecticides like Monocrotophos or Methyl dematon

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5. Dieback — Lasiodiplodia theobromae (Botryodiplodia theobromae)

Symptoms:

• Drying of twigs from tip downwards
• Discolouration of bark, gum exudation
• Internal browning of vascular tissues

Management:

• Prune diseased branches 15 cm below the infection point
• Apply Bordeaux paste on cut ends
• Spray Copper oxychloride (0.3%)

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Citrus Diseases

1. Gummosis — Phytophthora parasitica, P. palmivora, P. citrophthora

Symptoms:

• Yellowing of leaves, followed by cracking of bark and profuse gumming on the surface
• Infected bark becomes completely rotten; tree dries owing to girdling effect
• Also called foot rot or collar rot when plant dies before fruits mature

Management:

• Scrape diseased portions with a sharp knife; disinfect cut surface with Mercuric chloride (0.1%) or Potassium permanganate (1%)
• Paint 1 m of stem above ground level with Bordeaux paste
• Drench with Ridomil MZ 72 @ 2.75 g/l or Aliette (2.5 g/l)
• Avoid injuries to crown roots during cultural operations

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2. Citrus Canker — Xanthomonas campestris pv. citri

Symptoms:

• Acid lime, lemon and grapefruit are most affected; rare on sweet oranges and mandarins
• Lesions are typically circular with yellow halo; appear on both sides of leaf
• Severe in acid lime (difference from scab)
• Twig lesions cause girdling and death; fruit lesions reduce market value

Management:

• Spray Streptomycin sulphate 500-1000 ppm or Phytomycin 2500 ppm or Copper oxychloride 0.2% at fortnightly intervals
• Control leaf miner when young flush is produced
• Prune badly infected twigs before monsoon onset

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3. Tristeza (Quick Decline) — Citrus Tristeza Virus (CTV)

Symptoms:

• Lime is susceptible both as seedling or buddling on any root stock
• Rangpur lime root stock is tolerant to CTV
• Rapid wilting on sour orange rootstocks; honeycombing below bud union
• Bark eruption and pittings on stem, chlorosis of leaves, phloem necrosis
• Vector: Toxoptera citricida (aphid); also spread through infected bud wood

Management:

• Use CTV-free budwood for propagation
• Cross-protect with mild strains
• Use tolerant rootstocks (Rangpur lime, trifoliate orange)

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4. Citrus Greening (HLB) — Candidatus Liberibacter asiaticum

Symptoms:

• Affects almost all citrus varieties irrespective of rootstock
• Stunting, sparse foliation, twig dieback, predominantly greened worthless fruits
• Leaves become leathery with prominent veins and dull olive green colour
• Green circular dots on leaves; fruits small, lopsided with curved columella
• Vector: Citrus psyllid (Diaphorina citri)

Management:

• Control psyllids with insecticides
• Use pathogen-free bud wood for propagation
• Spray Tetracycline 500 ppm at fortnightly intervals

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5. Blastomenia — Phytoplasmal Disease

Symptoms:

• Reduced leaf size
• Leaves forming cluster-like bouquet
• Chlorotic clustering of leaves

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Banana Diseases

1. Panama Wilt — Fusarium oxysporum f.sp. cubense

Economic Importance:

• First major disease of banana; named “Panama disease” after the area where it first became serious
• Soil-borne fungal disease; enters through roots and wounds caused by nematodes

Symptoms:

• Yellowing of lower leaves from margin to midrib
• Hanging of leaves around pseudostem
• Withering of leaves; fruits turning bottle-shaped

Management:

• Avoid susceptible cultivars: Rasthali, Monthan, Red banana, Virupakshi
• Grow resistant cultivar Poovan

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2. Moko Disease — Pseudomonas solanacearum / Burkholderia solanacearum

Symptoms:

• Leaves become yellow and progress upwards; petiole breaks and leaves hang
• Vascular discolouration: pale yellow to dark brown
• Internal rot of fruits with dark brown discoloration
• Pseudostem cut transversely shows bacterial ooze

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3. Bunchy Top — Banana Bunchy Top Virus (BBTV)

Symptoms:

• Plants extremely stunted; leaves reduced in size with marginal chlorosis and curling
• Leaves become upright, brittle, and crowded at the top
• If infected early, no bunch is produced
• Transmitted primarily by infected suckers; vector: Aphid (Pentalonia nigronervosa)

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4. Sigatoka Leaf Spot — Cercospora musicola (Fungus)

Symptoms:

• Light yellow oval spots on leaves; centre of spot dies, turning light grey surrounded by brown ring
• Spots coalesce, killing large portions of leaves

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5. Kokkan Disease — Banana Bract Mosaic Virus

• Transmitted by aphid Pentalonia nigronervosa
• Pinkish streaks on pseudostem of 2-3 month old plants
• Late or failure of bunch appearance

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Papaya Diseases

1. Foot Rot / Stem Rot — Pythium aphanidermatum

Symptoms:

• Water-soaked spot on stem at ground level which enlarges and girdles the stem
• Diseased area turns brown or black and rots
• Terminal leaves turn yellow and droop; entire plant topples and dies
• Common in 2-3 year old trees; favoured by rain

Management:

• Seed treatment with Thiram or Captan 4 g/kg or Chlorothalonil
• Drench with Copper oxychloride 0.25% or Bordeaux mixture 1% or Metalaxyl 0.1%
• Avoid direct contact of water with stem

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2. Papaya Ring Spot — Viral

• Upper leaves of papaya are mottled
• Transmitted by aphids (Aphis gossypii)

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3. Papaya Leaf Curl — Viral

• Transmitted by whiteflies
• Curling and crinkling of leaves

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4. Powdery Mildew — Oidium caricae

• White powdery growth on leaf surfaces

5. Anthracnose — Colletotrichum gloeosporioides

• Same pathogen as mango anthracnose

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Pomegranate Diseases

1. Bacterial Blight — Xanthomonas axonopodis pv. punicae

• Also known as nodal blight, black spot, or “oily spot/Telya” in Maharashtra
• Water-soaked lesions on leaves, stems and fruits
• One of the most devastating diseases of pomegranate in India

2. Wilt — Ceratocystis fimbriata

• Sudden wilting and drying of branches
• Internal discolouration of wood

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Apple Diseases

1. Scab — Venturia inaequalis

Symptoms:

• Appears on leaves and fruits as olivaceous spots which turn dark brown to black and become velvety
• On young foliage, spots have radiating appearance with feathery edge
• Severe infection: leaf blade curved, dwarfed and distorted
• On mature fruits, centre of spots becomes corky with yellow halo around lesions

Other Apple Diseases/Disorders:

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Guava Diseases

1. Anthracnose — Colletotrichum gloeosporioides

• Symptoms observed on mature fruits on the tree
• Sunken, dark-coloured, necrotic lesions on fruits

2. Guava Rust — Puccinia psidii

• Affects foliage, young shoots, inflorescences and fruit
• Symptoms: distortion, defoliation, reduced growth
• On fully expanded leaves: dark bordered, roughly circular brown lesions with yellow halos

3. Wilt — Fusarium oxysporum f.sp. psidii

• Wilting and drying of entire tree
• Yellowing of leaves followed by desiccation

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Ber Diseases

1. Powdery Mildew — Oidium erysiphoides f.sp. zizyphi

Symptoms:

• White powdery mass on developing young leaves causing them to shrink and defoliate
• Small white powdery growth on young fruits which enlarge, coalesce and turn brown to dark brown
• In severe cases, entire fruit surface covered with powdery mass

2. Alternaria Leaf Spot — Alternaria chartarum

• Small irregular brown spots on upper leaf surface
• Dark brown to black spots on lower surface; spots coalesce into big patches
• Diseased leaves drop; plant debris serves as source of primary infection

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Grape Diseases

1. Downy Mildew — Plasmopara viticola

Symptoms:

• Irregular, yellowish, translucent spots on upper surface of leaves
• Correspondingly on lower surface: white powdery growth

Management:

• Spray Bordeaux mixture 1% or Metalaxyl + Mancozeb 0.4%

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2. Powdery Mildew — Uncinula necator

Symptoms:

• Powdery growth mostly on upper surface of leaves
• Malformation and discolouration of affected leaves

Management:

• Spray Inorganic sulphur 0.25% or Chinomethionate 0.1% or Dinocap 0.05%

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3. Anthracnose — Elsinoe ampelina

• Also called bird’s eye rot
• Dark spots with grey centres on berries resembling a bird’s eye

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Coffee Rust — Hemileia vastatrix

Symptoms:

• Mostly affects leaves and sometimes tender shoots
• In earlier stage, 2-3 mm yellow spots develop on lower surface of leaves
• Rust lesions develop as orange-yellow spots on lower surface; thousands of small rust pustules appear
• Upper surface of leaves turns yellow to brown

Management:

• Spray Bordeaux mixture 0.5% or Copper oxychloride
• Plant resistant varieties
• Maintain proper shade and spacing

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Quick Reference: Fruit Crop Diseases

Complete Disease-Pathogen Summary Table

Crop	Disease	Pathogen	Type	Key Diagnostic Feature
Mango	Anthracnose	C. gloeosporioides	Fungal	Black necrotic areas, dieback, deblossoming
Mango	Powdery mildew	Oidium mangiferae	Fungal	White powdery growth on panicles/flowers
Mango	Malformation	Fusarium moliliforme	Fungal	Bunchy top, floral malformation; bud mite vector
Mango	Sooty mould	Capnodium mangiferae	Fungal	Black encrustation on leaves (honeydew)
Citrus	Gummosis	Phytophthora spp.	Oomycete	Bark cracking, profuse gumming, foot rot
Citrus	Canker	X. campestris pv. citri	Bacterial	Circular lesions with yellow halo on both leaf sides
Citrus	Tristeza	CTV	Viral	Quick decline, honeycombing; aphid vector
Citrus	Greening/HLB	Ca. Liberibacter	Bacterial	Greened fruits, blotchy mottle; psyllid vector
Banana	Panama wilt	F. oxysporum f.sp. cubense	Fungal	Yellowing from margin, bottle-shaped fruits
Banana	Moko	Burkholderia	Bacterial	Bacterial ooze, internal fruit rot
Banana	Bunchy top	BBTV	Viral	Stunting, crowded upright leaves; aphid vector
Banana	Sigatoka	Cercospora musicola	Fungal	Yellow oval spots, grey centre, brown ring
Papaya	Foot rot	Pythium aphanidermatum	Oomycete	Water-soaked stem base, toppling
Papaya	Ring spot	Viral	Viral	Mottled leaves; aphid vector
Papaya	Leaf curl	Viral	Viral	Curling leaves; whitefly vector
Pomegranate	Bacterial blight	X. axonopodis pv. punicae	Bacterial	Oily spots (Telya), nodal blight
Apple	Scab	Venturia inaequalis	Fungal	Olivaceous velvety spots, feathery edge
Apple	Fire blight	Erwinia amylovora	Bacterial	Burnt appearance of blossoms/shoots
Guava	Anthracnose	C. gloeosporioides	Fungal	Sunken necrotic lesions on fruits
Guava	Rust	Puccinia psidii	Fungal	Brown lesions with yellow halo
Ber	Powdery mildew	Oidium erysiphoides	Fungal	White powdery mass on leaves/fruits
Grape	Downy mildew	Plasmopara viticola	Oomycete	Yellow spots above, white growth below
Grape	Powdery mildew	Uncinula necator	Fungal	Powdery growth on upper leaf surface
Coffee	Rust	Hemileia vastatrix	Fungal	Orange-yellow spots on lower leaf surface

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Key Exam Points to Remember

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Summary Cheat Sheet