Pests & Diseases
What causes brown spots on plant leaves?
The short answer
Identify the plant and compare internal spots with dry leaf margins. Disease, heat, root-zone stress and physical injury can look similar. Spot shape or color alone cannot distinguish a fungus from bacteria or select a treatment; use host-specific guidance.
Brown spots are a symptom rather than a diagnosis. Their size, edge, location, and spread can help separate water stress, leaf scorch, pests, and disease.
Match the pattern before acting
Dry margins or exposed patches
- Damage follows moisture or weather stress
Check water delivery and shelter; not every brown area is infectious.
New or expanding internal lesions
- Repeated spots on several leaves, sometimes with early drop
Use plant-specific leaf-spot guidance; fungal and bacterial patterns overlap.
Stable exposure injury
- Damage followed a recorded event; new growth remains unaffected
Stop the suspected exposure and monitor rather than spraying from appearance alone.
Checks before choosing a response
- Identify the plant and inspect several leaves on both surfaces, including healthy neighbors. Record which parts of the plant are affected.
- Check root-zone moisture, drainage and recent heat, wind, frost or spray exposure; compare timing with the first damage.
- Photograph the same leaves over subsequent checks. New or expanding lesions differ from old stable injury.
What to do now
- Correct a documented moisture or exposure problem gradually and preserve healthy foliage.
- If leaf-spot disease is plausible, reduce leaf wetness and splash and collect fallen affected leaves where practical.
- Use the plant-specific continuations below; keep photographs and care history for diagnosis if uncertain.
GardenSolved checkpoint
Do not do this yet
- Do not identify a pathogen from round or angular spot shape alone.
- Do not spray fungicide, copper or homemade remedies before identifying the host and likely problem.
- Do not assume water droplets explain every sun-exposed mark or remove all foliage because some leaves are spotted.
Confirm the likely cause first, then choose the treatment.
When to investigate further
Rapid spread, extensive premature leaf loss, stem injury or whole-plant wilt needs host-specific assessment; isolate movable plants when practical.