Leaf Spot 🦠
At a glance
- Cause: A symptom pattern, not one single disease
- Tell-tale sign: Discrete brown, black, tan, or yellow-haloed spots on leaves
- Severity: Usually cosmetic unless spots spread fast, merge, or cause heavy leaf drop
How to identify
Leaf spot is a broad symptom: small to large spots on leaves caused by fungi, bacteria, insects, sun, salts, or stress. Look at the pattern. Round or target-like spots often suggest fungal disease; angular water-soaked spots suggest Bacterial Leaf Spot; spots following veins or appearing after wet spring weather may point to Anthracnose.
What causes it
Different hosts have different leaf spot organisms. Wet leaves, crowded foliage, poor airflow, overhead watering, and stressed plants make many spots worse.
Treatment & management
Following Integrated Pest Management:
- Remove badly spotted leaves if the plant can spare them.
- Keep foliage dry: water the soil, not the leaves.
- Improve airflow by spacing, pruning, or using gentle indoor circulation.
- Clean fallen leaves so spores and bacteria do not persist.
- Avoid guessing with sprays unless the cause is clear and the plant is valuable.
Prevention
Reduce leaf wetness, avoid crowding, and keep plants correctly watered. Many leaf spots are managed more by conditions than by products.
Affects (in this guide)
Many houseplants, ornamentals, natives, vegetables, and trees