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Rust: How to Identify, Control, and Prevent Garden Diseases | The Old Farmer's Almanac

Rust Plant Disease

Caption

Fungal rust disease infiltrates these spinach leaves.

Photo Credit
Rust photo by Howard F. Schwartz via Wikimedia Commons
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How to Identify and Control Rust Plant Disease

The Editors
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What is rust plant disease? This fungal disease affects a wide range of woody and herbaceous plants. Even though it rarely kills plants, it reduces a plant’s health, vigor, and flower production.

What Causes Rust?

Rust disease is caused by a fungal parasite that needs living plants to survive. Rust diseases occur most often in mild, moist conditions. Rust is spread by spores that are transferred from infected plants to healthy plants. These spores can be transferred either by the wind or by water, which is why rust disease often spreads after watering. Wet surfaces are also needed to cause infections.

Identification

How to Identify Rust Damage

Rust diseases come in different varieties and can affect a wide range of plants. People often struggle with rust on their roses. It is easy to remember the defining characteristics of this fungus, as they match its name. Rust plant disease will look similar to the rust that appears on that old bicycle in the shed.

  • Look for yellow or white spots forming on the upper leaves of a plant.
  • Look for reddish to orange blister-like swellings called pustules on the undersides of leaves.
  • Orange or yellow spots or streaks appear on the undersides of the leaves.
  • Within these spots that form are spores.
  • Usually leaf distortion and defoliation occur.

rust-fungus-identification.jpg

Photo Credit: Bruce Watt, University of Maine. Small pustules appear on the undersides, and sometimes the tops, of leaves when a plant is infected with rust.

Control and Prevention

How to Control Rust Fungi

Unfortunately, there is no easy treatment for rust. Try these tips:

  • Remove all infected parts and destroy them. For bramble fruits, remove and destroy all the infected plants and replant the area with resistant varieties.
  • Clean away all debris in between plants to prevent rust from spreading.
  • Avoid splashing water onto the leaves, as this can help spread rust.

Rust Prevention

  • Dust your plants with sulfur early in the season to prevent infection or to keep mild infections from spreading.
  • Space your plants properly to encourage good air circulation.
  • Avoid wetting the leaves when watering plants.
  • There are many effective rust fungicides you can try. Ask your local nursery for which products you should use.

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