Diseases
Leaf Spot Disease Complexes
Leaf spots and lesions can be produced by fungal, bacterial, environmental, chemical, and physical causes. Pattern, progression, environmental context, and laboratory evidence are often needed to separate them.
What to look for
- Lesion shape, margin, color, and tissue age
- Whether spots cross veins or follow splash patterns
- New lesions appearing after wet periods
- Visible sporulation or structures under magnification when present
Important look-alikes
- Foliar spray injury
- Nutrient or salt-related necrosis
- Mechanical punctures
- Pest feeding
How to confirm
- Track lesion progression over time
- Inspect both leaf surfaces with magnification
- Review recent sprays and environmental wetness
- Use diagnostic testing when the outbreak is important or unusual
Management principles
- Avoid assuming every spot is a deficiency
- Reduce unnecessary leaf wetness and splash where relevant
- Remove heavily diseased tissue when appropriate
- Use confirmed diagnosis to choose further action
Prevention
- Maintain sanitation and airflow
- Avoid moving contaminated splash water
- Inspect incoming material
- Record foliar applications and environmental events
Visual study guide
- Leaf lesion vocabulary plate
- Biotic versus spray-injury comparison
- Splash pattern diagram
- Magnified lesion inspection guide