Peacock Plant with Alternaria Leaf Spot: Prevention & Cure
Calathea makoyana
Alternaria leaf spot is a common fungal disease caused by Alternaria solani and Alternaria alternata that affects a wide range of plants including tomatoes, potatoes, brassicas, and ornamentals. The disease thrives in warm, humid conditions and can cause significant crop damage if left untreated. Spores overwinter on plant debris and can attach to seeds, making complete elimination difficult.
ð Symptoms
- âĒ Small dark circular spots (0.5-0.75 inches diameter) on leaves
- âĒ Concentric rings forming target-like patterns
- âĒ Spots change from black to tan/gray with yellow halos
- âĒ Fuzzy texture develops as fungus produces spores
- âĒ Premature leaf wilting and drop
- âĒ Brown or black spots on fruits and stems
- âĒ Weakened plants and reduced vigor
â Possible Causes
- â Fungal pathogens Alternaria solani and Alternaria alternata
- â Warm temperatures (60-80°F) with high humidity
- â Overhead watering creating prolonged leaf wetness
- â Dense plant spacing limiting air circulation
- â Plant stress from nutrient deficiency or drought
- â Overwintering spores on plant debris
- â Contaminated seeds carrying fungal spores
ð Treatment
Quick Fixes
Step 1
Remove heavily infected leaves immediately
Step 2
Apply chlorothalonil or mancozeb protectant fungicide to all plant surfaces
Step 3
Ensure thorough coverage including leaf undersides
Step 4
Reapply every 7 days or after rain
Step 5
Switch to azoxystrobin systemic fungicide after 2 applications for resistance management
Step 6
Continue treatment for 2 weeks after symptoms clear
Organic Treatment
Step 1
Remove all visible infected leaves and plant debris, dispose in sealed bags
Step 2
Apply Bacillus subtilis biological fungicide spray, covering all leaf surfaces thoroughly
Step 3
Spray copper fungicide (organic-approved copper hydroxide or oxychloride) on remaining foliage
Step 4
Apply straw mulch around plant base to prevent soil splash
Step 5
Reapply biological spray every 5-7 days
Step 6
Reapply copper spray every 7-10 days
Step 7
Continue monitoring and treatment for 3-4 weeks
ðĄïļ Prevention
- â Remove and destroy infected plant debris immediately
- â Practice 3-4 year crop rotation with non-host plants
- â Space plants properly for good air circulation
- â Water at soil level, avoid overhead irrigation
- â Apply straw mulch immediately after planting
- â Use certified disease-free seeds and transplants
- â Avoid working with wet plants to prevent spore spread
- â Maintain plant health through proper fertilization
ðą Care Guide: Peacock Plant
ð§ How to Water
Keep the substrate slightly moist, watering when the top 1-2 inches are dry. Use distilled, filtered, or rainwater, as the plant is sensitive to chlorine and fluoride. In winter, reduce frequency to once a week.
âïļ Lighting
Prefers abundant indirect light, avoiding direct sun that can burn delicate leaves. Ideal for east or north-facing rooms. Tolerates partial shade, but with abundant indirect light it will produce more healthy leaves.
ðŠī Ideal Soil
Substrate rich in organic matter with good drainage. An ideal mix contains 50% potting soil, 25% orchid bark, and 25% perlite. pH should be slightly acidic (5.5-6.5).