Leaf Spots and Discoloration: Causes & Solutions

Leaf discoloration can be a warning sign of plant health issues, from nutrient deficiencies to fungal infections. Understanding the cause is key to restoring your plant's health.

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Common Causes of Leaf Spots and Discoloration

1. Fungal Infections (Leaf Spot, Powdery Mildew)

Fungal infections thrive in humid environments and often spread through water droplets.

• Symptoms: Small brown, black, or yellow spots with irregular edges; powdery white coating on leaves.
• How to Diagnose: If the spots spread rapidly and appear fuzzy or powdery, a fungal infection is likely.
• How to Fix It:
  • Remove affected leaves to prevent spread.
  • Increase air circulation around the plant. Consider using a small fan to help with air movement.
  • Use a fungicide or neem oil to treat the infection.

2. Bacterial Leaf Spot

Bacterial infections often cause dark, wet-looking spots that may spread quickly.

• Symptoms: Dark, water-soaked lesions on leaves, often surrounded by a yellow halo.
• How to Diagnose: Spots often look greasy or mushy and may expand under humid conditions.
• How to Fix It:
  • Prune infected leaves immediately.
  • Avoid overhead watering to reduce moisture on leaves.
  • Use a copper-based bactericide for treatment.

3. Sunburn or Light Stress

Excessive sunlight can scorch plant leaves, especially in delicate indoor plants.

• Symptoms: White, tan, or bleached patches on leaves, often on the side exposed to the sun.
• How to Diagnose: If the damage appears after sudden sun exposure or relocation, sunburn is the likely cause.
• How to Fix It:
  • Move the plant to a location with indirect light.
  • Gradually acclimate the plant to brighter light if needed.
  • Trim off damaged leaves if necessary.

4. Nutrient Deficiencies

Plants require specific nutrients for healthy growth. Deficiencies can cause discoloration.

• Symptoms: Yellowing, purpling, or browning leaves depending on the nutrient lacking.
• How to Diagnose: Look for patterns—yellowing between veins (iron deficiency), purpling on older leaves (phosphorus deficiency).
• How to Fix It:
  • Use a balanced fertilizer with essential nutrients.
  • Ensure proper soil pH for nutrient absorption.

5. Pest Damage (Thrips, Spider Mites)

Pests can cause leaf discoloration by feeding on plant sap.

• Symptoms: Small yellow specks, webbing, or stippled appearance on leaves.
• How to Diagnose: Check leaf undersides for tiny insects or fine webbing.
• How to Fix It:
  • Rinse the plant with water to remove pests. A gentle garden hose nozzle may assist with this.
  • Apply insecticidal soap or neem oil.
  • Introduce beneficial insects like ladybugs.

Preventing Leaf Discoloration

• Water Smartly: Avoid overhead watering to prevent fungal and bacterial infections.
• Maintain Airflow: Ensure proper spacing between plants to reduce humidity issues.
• Monitor Light Exposure: Adjust placement to avoid direct sunburn or low-light stress.
• Use Proper Fertilization: Apply balanced nutrients according to plant needs.

Need More Help?

If you're still unsure about what's causing your plant's leaf discoloration, try the Leafwise Plant Health Diagnosis Tool for a personalized assessment.