Any infection or condition caused by pathogens (fungi, bacteria, viruses) or environmental stress that damages plant tissue, reducing growth, yield, or aesthetic appeal.
In plain terms
Plant diseases are caused by pathogens (fungi, bacteria, viruses) or environmental stress. Fungal diseases are most common; bacterial and viral diseases are less common but often more serious. Diseases spread via spores, water splash, insects, or contaminated tools. Prevention (good sanitation, resistant varieties, air circulation) is more effective than cure.
Why this matters
Understanding disease causes helps you prevent and manage them. Prevention beats trying to cure established diseases.
In practice
Examples
Powdery mildew: fungal disease; prevented with air circulation; cured with fungicide if severe.
Fire blight: bacterial disease; prevented with sanitation; no cure once established (must prune out).
Virus: spreads via insects; no cure; prevention (controlling aphids) is only option.
Root rot: fungal disease; prevented with good drainage; no cure once established.
Practical applications
Scout regularly for early disease signs.
Remove infected leaves immediately; slows spread.
Improve air circulation with pruning and spacing.
Use resistant varieties when available.
Sterilize tools between cuts (10% bleach) to prevent spread.