Angular bacterial leaf spot

Angular leaf spot is a bacterial infection that destroys leaf tissues from within. Bacteria enter through natural leaf pores (stomata) and multiply, producing oily or water-soaked lesions that block photosynthesis. Without intervention, spots enlarge, turn brown and black, then dry out, causing premature leaf drop and seriously weakening the plant.

Signs to check

• Clearly polygonal spots whose edges are bounded by leaf veins.
• Spots initially look water-soaked, oily or translucent.
• Color changes from dark green to brown-black or gray as lesions dry.
• A pale yellow halo frequently surrounds older spots.
• The centers of old spots may break down and fall out, leaving holes in the leaf.

What you may notice

• Angular leaf spots · Wet-looking spots appear on leaves, their polygonal shape sharply bounded by the veins.
• Spots with a yellow halo · Circular spots, often brown or black in the center, are surrounded by a distinct yellow halo on the leaves.
• Gray spots with dark edges · Spots with pale gray or beige centers form on leaves, surrounded by a distinct dark brown border.
• Stem spots · Abnormally colored marks of varying shapes and sizes appear on the plant's stems.

What to do now

Stop bacterial leaf spot

1. Isolate the infected plant immediately to prevent spread to your other plants.
2. Cut off and discard every spotted leaf. Use pruning shears or scissors sterilized with alcohol between every cut to avoid spreading bacteria.
3. Change your watering technique: water the potting mix directly at the base of the plant. Avoid wetting the foliage at all costs.
4. Ensure good air circulation around the plant by spacing it away from others. Good airflow helps leaves dry quickly.
5. Apply a copper-based bactericide, following the manufacturer's instructions carefully. This protects healthy leaves; it does not cure leaves already affected.
6. Stop all misting. Spraying water on leaves creates ideal conditions for bacterial growth.
7. Watch the plant closely over the following weeks and remove any new suspicious leaf as soon as it appears.

Prevention

• Always water at the base of the plant, never over the foliage.
• Ensure good air circulation between plants so they dry quickly.
• Immediately remove dead or damaged leaves from the pot and the potting mix surface.
• Disinfect pruning tools with alcohol before and after every use.