Diseases In Plants

Diseases are seen in plants. Let us have a look at some plants:

~Rice: 

1)Blast Disease:
Introduction: Caused by the fungus Magnaporthe oryzae, blast disease affects leaves, nodes, panicles, and other parts of the rice plant.
Symptoms: Small, water-soaked lesions on leaves, which later turn into spindle-shaped or diamond-shaped lesions with gray centers. Infected panicles show white to gray spores.
Disease Cycle: The fungus survives in infected plant debris and soil. Spores are spread through water and wind.
Epidemiology: Favorable conditions include high humidity, moderate temperatures, and waterlogged fields.
Management: Plant resistant varieties, practice crop rotation, use fungicides.

2)Brown Spot:

Introduction: Caused by the fungus Cochliobolus miyabeanus, brown spot affects leaves, reducing photosynthetic efficiency.
Symptoms: Oval to spindle-shaped lesions with brown centers and yellow halos on leaves.
Disease Cycle: The fungus survives in infected plant debris and soil. Spores are spread through wind and rain.
Epidemiology: Warm and humid conditions favor disease development.
Management: Plant resistant varieties, use fungicides, practice proper field sanitation.

3)Sheath Blight:
Introduction: Caused by the fungus Rhizoctonia solani, sheath blight affects leaf sheaths, reducing grain yield.
Symptoms: Water-soaked lesions on leaf sheaths, which later turn brown with a fluffy white mycelium.
Disease Cycle: The fungus survives in infected plant debris and soil. Spread occurs through contaminated equipment and water.
Epidemiology: Warm and humid conditions promote disease development.
Management: Plant resistant varieties, practice proper irrigation management, use fungicides.

4)Rice Tungro Diseases
Introduction: Caused by a complex of two viruses, Rice tungro disease affects both rice plants and their insect vectors.
Symptoms: Stunted growth, yellowing of leaves, and reduced tillering. Infected plants may exhibit characteristic "hopperburn."
Disease Cycle: Spread by insect vectors, mainly leafhoppers (Nephotettix spp.) and planthoppers (Nilaparvata lugens).
Epidemiology: High vector populations and conducive environmental conditions favor disease spread.
Management: Use resistant varieties, eliminate weed hosts, practice vector control measures.

5)Rice Stem Rot:
Introduction: Caused by the fungus Sclerotium oryzae, rice stem rot affects stems and roots, leading to lodging and yield loss.
Symptoms: Water-soaked lesions on stems, which later become brown and sunken. White mycelium and sclerotia may be present.
Disease Cycle: The fungus survives as sclerotia in soil. Spread occurs through contaminated soil and water.
Epidemiology: Warm and wet conditions favor disease development.
Management: Rotate crops, improve drainage, use fungicides.

~Wheat:

1)Stripe Rust:
Introduction: Caused by the fungus Puccinia striiformis, stripe rust affects wheat leaves, reducing photosynthetic efficiency.
Symptoms: Yellow to orange stripes or pustules on leaves, which may coalesce under favorable conditions.
Disease Cycle: The fungus survives as spores on alternate hosts and can be windborne over long distances.
Epidemiology: Cool and moist conditions favor disease development.
Management: Plant resistant varieties, apply fungicides preventively, practice crop rotation.

2)Powdery Mildew:
Introduction: Caused by various species of the fungus Blumeria graminis, powdery mildew affects wheat leaves and stems, reducing photosynthesis and weakening the plant.
Symptoms: White powdery patches on leaves, which may later turn yellow or brown. Infected stems may show powdery growth as well.
Disease Cycle: The fungus survives as spores in infected plant debris and can be spread by wind.
Epidemiology: Warm days and cool nights with high humidity favor disease development.
Management: Plant resistant varieties, practice crop rotation, apply fungicides.

3)Fusarium Head Blight (Scab):
Introduction: Caused by various species of Fusarium fungi, fusarium head blight affects wheat heads, reducing grain yield and quality.
Symptoms: Bleached or discolored heads, often with pink or orange fungal growth. Infected grains may be shrunken and moldy.
Disease Cycle: The fungus survives in infected crop debris and soil. Spread occurs through rain splashes and infected seeds.
Epidemiology: Warm and humid conditions during flowering favor disease development.
Management: Use resistant varieties, practice crop rotation, apply fungicides.

4)Fusarium Head Blight (Scab):

Introduction: Caused by various species of Fusarium fungi, fusarium head blight affects wheat heads, reducing grain yield and quality.
Symptoms: Bleached or discolored heads, often with pink or orange fungal growth. Infected grains may be shrunken and moldy.
Disease Cycle: The fungus survives in infected crop debris and soil. Spread occurs through rain splashes and infected seeds.
Epidemiology: Warm and humid conditions during flowering favor disease development.
Management: Use resistant varieties, practice crop rotation, apply fungicides.

~Maize:

1.Maize Streak Virus (MSV):

Introduction: Caused by various strains of the Mastrevirus species, MSV affects maize plants, leading to stunted growth and reduced yield.
Symptoms: Streaks of yellow or white discoloration along leaf veins, stunting, and malformed ears.
Disease Cycle: Transmitted by leafhopper vectors (e.g., Cicadulina spp.) and through infected seeds.
Epidemiology: Warm temperatures and vector presence favor disease spread.
Management: Use virus-free seeds, practice vector control measures.

2.Maize Dwarf Mosaic Virus (MDMV):

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Maize:

3.Maize Streak Virus (MSV):

Introduction: Caused by various strains of the Mastrevirus species, MSV affects maize plants, leading to stunted growth and reduced yield.
Symptoms: Streaks of yellow or white discoloration along leaf veins, stunting, and malformed ears.
Disease Cycle: Transmitted by leafhopper vectors (e.g., Cicadulina spp.) and through infected seeds.
Epidemiology: Warm temperatures and vector presence favor disease spread.
Management: Use virus-free seeds, practice vector control measures.
4.Maize Dwarf Mosaic Virus (MDMV):

Introduction: Caused by several viruses including Sugarcane mosaic virus and Maize dwarf mosaic virus strain A and B, MDMV leads to stunted plants with mottled leaves.
Symptoms: Yellow streaks or mottling on leaves, stunted growth, and reduced ear size.
Disease Cycle: Transmitted by aphids, primarily the corn leaf aphid (Rhopalosiphum maidis), and through infected seeds.
Epidemiology: Warm temperatures and aphid presence favor disease spread.
Management: Use virus-free seeds, practice aphid control measures.

5.Gray Leaf Spot:

Introduction: Caused by the fungus Cercospora zeae-maydis, gray leaf spot affects maize leaves, reducing photosynthetic efficiency and yield.
Symptoms: Small, rectangular lesions with gray centers and dark brown borders on leaves, which may coalesce under favorable conditions.
Disease Cycle: The fungus survives in infected crop debris and soil. Spread occurs through wind and rain.
Epidemiology: Warm and humid conditions favor disease development.
Management: Plant resistant varieties, practice crop rotation, use fungicides.

6.Northern Corn Leaf Blight:

Introduction: Caused by the fungus Setosphaeria turcica, northern corn leaf blight affects maize leaves, reducing photosynthetic efficiency and yield.
Symptoms: Large, elongated lesions with wavy edges and tan centers on leaves, which may cover large areas of the leaf surface.
Disease Cycle: The fungus survives in infected crop debris and soil. Spread occurs through wind and rain.
Epidemiology: Warm and humid conditions favor disease development.
Management: Plant resistant varieties, practice crop rotation, use fungicides.

7.Common Rust:

Introduction: Caused by the fungus Puccinia sorghi, common rust affects maize leaves, reducing photosynthetic efficiency and yield.
Symptoms: Small, round to elongated pustules containing orange to brown spores on leaves, which may coalesce under favorable conditions.
Disease Cycle: The fungus survives as spores in infected crop debris and soil. Spread occurs through wind.
Epidemiology: Warm temperatures and high humidity favor disease development.
Management: Plant resistant varieties, practice crop rotation, use fungicides.

Author: Birendra Kumar Shah
Affiliation: Gauriganj Secondary School,
Gauriganj, Jhapa