📈 Diseases of Ornamental Crops

Ornamental crops have high aesthetic-value standards, so even mild disease symptoms can cause major market losses. Effective control depends on sanitation, microclimate management, and timely fungicidal protection.

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Rose Diseases

Black Spot

Causal organism: Diplocarpon rosae

• Circular black spots with fringed margins on upper leaf surface
• Severe infection causes defoliation and weakens the bush
• Favored by warm, humid weather with leaf wetness
• Spray Mancozeb (0.2%) or Hexaconazole (0.05%) at 10-day intervals

Powdery Mildew

Causal organism: Podosphaera pannosa

• White powdery coating on leaves, buds, and young shoots
• Leaves curl, distort, and drop prematurely
• Flower buds may fail to open or produce deformed flowers
• Spray Karathane (0.05%) or Triadimefon (0.1%)

Die-Back

Causal organism: Diplodia roseae

• Progressive drying of shoots from tip downward
• Bark turns brown to black; pith becomes discolored
• Prune affected shoots 2–3 cm below the diseased portion; apply Bordeaux paste to cut ends

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Chrysanthemum Diseases

Leaf Spot

Causal organism: Septoria chrysanthemi

• Dark brown to black circular spots on lower leaves first
• Spots may coalesce, causing premature leaf fall
• Spray Mancozeb (0.2%) at fortnightly intervals

Wilt

Causal organism: Fusarium oxysporum f.sp. chrysanthemi

• One-sided yellowing and wilting progressing upward
• Vascular browning visible when stem is cut
• Use disease-free cuttings; Trichoderma soil treatment

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Gladiolus Diseases

Fusarium Corm Rot

Causal organism: Fusarium oxysporum f.sp. gladioli

• Brown, sunken lesions on corms during storage
• Plants show yellowing and wilting from lower leaves upward
• Corm treatment with Carbendazim (0.2%) for 30 minutes before planting
• Crop rotation for 3–4 years

Botrytis Blight

Causal organism: Botrytis gladiolorum

• Water-soaked spots on petals during humid weather
• Grey mold on flowers and leaves
• Remove and destroy affected flowers; improve air circulation

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Marigold — Damping Off and Leaf Spot

• Damping off (Pythium, Rhizoctonia): Seedling mortality in nursery beds; avoid overwatering
• Leaf spot (Alternaria): Concentric-ringed spots on leaves; spray Mancozeb

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General IDM for Ornamentals

1. Use disease-free planting material (certified cuttings, bulbs, corms)
2. Maintain proper spacing for air circulation
3. Avoid overhead irrigation — use drip or basal watering
4. Remove and destroy diseased plant parts promptly
5. Protective fungicide sprays during humid weather
6. Soil solarization in nursery beds before planting

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Summary Cheat Sheet

Crop Group	Major Disease	Hallmark Symptom	Core Management
Rose	Black spot/powdery mildew/die-back	Black spots, white growth, shoot die-back	Pruning + fungicide rotation + sanitation
Chrysanthemum	Leaf spot/wilt	Leaf spotting and vascular wilt	Clean cuttings + foliar protection
Gladiolus	Corm rot/Botrytis blight	Corm lesions and grey floral mould	Corm treatment + humidity management
Marigold	Damping off/leaf spot	Seedling collapse and concentric spots	Nursery hygiene + preventive sprays

References

2 sources • [1] [2]

[1]

Indian Council of Agricultural Research (ICAR)

Official

[2]

CABI Crop Protection Compendium

Website