Plant Disease Symptoms: Necrosis, Wilt, and Die-back

Plant Disease Symptoms

• Etiolation: Yellowing of plants due to lack of light
• Chlorosis: Yellowing of plants due to infection by viruses, bacteria, fungi, low temperature, or lack of iron
• Albino: Lack of pigmentation, resulting in white or bleached appearance
• Chromosis: Red, purple, or orange pigmentation due to physiological disorders

Exudation and Overgrowth

• Exudation: Masses of bacterial cells that ooze out to the surface of affected plant parts, forming drops or smears that dry to form a crust on the host surface
• Overgrowth: Excessive growth of plant parts due to infection by pathogens, caused by hyperplasia (abnormal increase in cell division) or hypertrophy (abnormal increase in cell size)

Atrophy and Sclerotia

• Atrophy: Inhibition of growth due to reduction in cell division or cell size, also known as hypoplasia or dwarfing
• Sclerotia: Dark, hard structures composed of dormant mycelia of some fungi, sometimes developed on affected plant parts, considered a sign of disease rather than a symptom

Necrosis, Wilt, and Die-back

• Necrosis: Death of cells, tissues, and organs resulting from infection by pathogens, manifesting as spots, blights, burns, cankers, streaks, stripes, damping-off, and rot
• Wilt: Withering and drooping of a plant starting from some leaves to the growing tip, caused by blockage in the translocation system due to pathogens
• Die-back: Drying of plant organs, starting from the tip and progressing towards the main stem or trunk

Mildew, Rusts, Smuts, and Blotch

• Mildew: White, grey, or brown superficial growth of the pathogen on the host surface
• Rusts: Numerous small pustules growing out through the host epidermis, giving a rusty appearance to the affected parts
• Smuts: Charcoal-like, black, or purplish-black dust-like masses developed on affected plant parts, mostly on floral organs and inflorescence
• Blotch: Large area of discolouration of a leaf, fruit, etc., giving a blotchy appearance

White Blisters and Colour Change

• White blisters: Numerous white, blister-like ruptures on the host epidermis, forming powdery masses of fungal spores
• Colour change: Conversion of green pigment of leaves into other colours, mostly yellow, in patches or covering entire leaves