Rust

Rust is a fungal disease that produces pustules filled with powdery orange to brown spores. The fungus feeds on leaf cells, weakening the plant by disrupting its ability to photosynthesize. Untreated, the infection spreads, causing yellowing, drying, and premature leaf drop, slowing overall growth.

Signs to check

• Small, raised, powdery pustules on the undersides of leaves.
• Orange or brown powder that comes off the pustules easily when touched.
• Yellow or discolored spots on the upper leaf surface, corresponding to the pustules underneath.
• The most infected leaves turn completely yellow, dry out, and fall.

What you may see

• Powdery orange pustules · Small, raised orange to rust-colored pustules appear on leaves and release a fine powder when touched.
• Diffuse yellow spots · Yellow to pale green areas of discoloration appear on leaves, with blurry, indistinct edges.

What to do now

Get rid of rust disease

1. Isolate the infected plant immediately to prevent spores from contaminating other plants.
2. Cut off and discard all leaves showing signs of rust. Use pruning shears disinfected with alcohol between cuts. Never put them in the compost.
3. Clean healthy leaves with a damp cloth to remove any spores that may have settled on them.
4. Prepare a baking soda solution: mix 5 mL (about 1 measuring teaspoon) of baking soda and 5 mL (about 1 measuring teaspoon) of black soap into 1 liter of water (about 1.06 US qt). Baking soda changes the pH on the leaf surface, preventing spores from germinating.
5. Spray the whole plant generously with the solution, paying particular attention to the undersides of leaves. Repeat every 7 to 10 days for at least one month.
6. Improve air circulation around the plant. Do not crowd it against other plants or a wall.

Prevention

• Water the plant directly at its base, avoiding wetting the foliage.
• Ensure good spacing between plants so air can circulate freely.
• Inspect the undersides of leaves on all your plants once a week for early signs.
• Clean and disinfect pruning tools after every use to avoid spreading disease.