From tomatoes to roses, many plants can suffer from the fungal disease known as rust. The symptoms of the various forms of rust include yellow to orange spots that appear powdery on the undersides of leaves. Later, yellow to brown spots may appear on the upper leaf surfaces. Rust "pustules" may also appear on stems and flowers. Wilting and curling of leaves is common. This disease often occurs in regions having cool, damp weather, such as the Pacific Northwest. Rust can be difficult to cure; prevention is the best approach.
Cut off all of the plant's leaves and other parts that show signs of rust. Rake fallen leaves near your plant. Place them in a garbage bag and dispose of them at your landfill, instead of adding them to your compost pile.
Water your plants from below instead of using a sprinkle, because the rust fungus spreads in water. Setting up a drip system or soaker hoses will keep water at the plant's root zone and prevent the leaves from becoming wet. However you choose to water, do so early in the day to allow water to evaporate and soak into the soil before the cooler evening hours.
Plant susceptible varieties at a sufficient distance apart to give them maximum airflow, which will help prevent rust spores from spreading.
Spray your susceptible plant with an approved fungicide beginning in early spring. Check with a garden supply store or your county extension agent for products approved for your location.
When you prune infected plants, dip your cutting blades in a solution of bleach and water, mixed in equal amounts, between each cut. Some plants, such as hollyhocks, benefit when you prune them to ground level in fall. Certain plants, such as the weed mallow, are especially prone to rust and can exacerbate its spread. Remove them from your garden.
If you choose sulphur spray to control rust, do not apply it when the daytime high is forecast to exceed 29.4 degrees C within 24 hours, because sulphur can damage leaves at high temperatures.