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Help for Rust on Plants

Master gardener Paul James shows how to prevent rust disease and keep it from spreading in your garden.

Rust doesn't only happen on metal surfaces. There's another kind of rust that gardeners deal with—the kind that attacks plants. Rust attacks a number of different plants, from trees and shrubs to annuals and perennials. This kind of rust is a pathogen, caused a number of different fungal diseases. Like most fungal diseases, once it appears on a plant it's difficult to control. The good news is that rust is more unsightly than insidious, meaning it rarely does permanent damage to plants.

There are several fungicides on the market that are used to treat rust. They rely on oil, copper, sulfur or even baking soda as their active ingredient. Unfortunately, once the rust is on leaf surfaces, fungicides limit only the spread of the disease. If you want to actually prevent its appearance, you have to begin spraying before it appears and continue spraying throughout the growing season. Do this as often as every seven to 10 days.

Because this can be very time-consuming, there are other options to consider.

  • At the first sign of rust, remove infected leaves and toss them in the trash, not the compost pile.
  • Water the base of plants with care to avoid splashing the foliage. Wet leaves can encourage the arrival of rust.
  • Provide good air circulation around plants, especially those near walls and fences.
  • Disinfect pruners with a mild bleach solution when pruning plants prone to rust.
  • Shop around for disease-resistant plants. Certain roses, for example, like rugosa roses are far less susceptible to rust than the more popular hybrid teas.

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