Getting rid of rust disease
What solutions are there to remedy this?
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Rust is a fungal disease that’s quite common, caused by microscopic fungi. It can affect a wide variety of plants: ornamental flowering plants (roses, hollyhocks, hyacinths, pelargoniums, chrysanthemums…), vegetables (garlic, potatoes, beans…), fruit trees (plum, pear…), currant bushes or conifers.
These fungi spread in spring, when temperatures become mild. They thrive in warm, humid conditions, and in confined environments (similar to powdery mildew in late summer). The fungus develops on one plant, then releases numerous spores that can reach other plants, dispersing via wind or simple contact.
What are the symptoms?
When a plant is affected by rust disease, discoloured spots appear on the upper surface of the leaves, along with orange or brown pustules (hence the name ‘rust’) on the underside and herbaceous stems. These can vary in colour depending on the infected plant. The spots darken by late summer and autumn. Often, the leaves eventually fall off.
The pustules release spores, leading to the spread of these fungi.
Rust weakens the plant, resulting in slower growth, limited flowering, and reduced fruit production… Not to mention the unsightly appearance of these orange spots. However, it is quite rare for the plant to die from it.
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Getting rid of rust diseaseHow to prevent rust disease?
A few precautions will help prevent the disease from appearing:
- Avoid placing susceptible plants in a confined, damp location, as these conditions encourage fungal growth.
- Water in the morning, preferably, and avoid wetting the foliage.
- When pruning, disinfect your tools (secateurs, shears, etc.) to prevent spreading the disease from one plant to another.
- Try to maximise air circulation (for example, if grown in a greenhouse) and avoid planting too densely.
- Choose vigorous, resistant plants.
- Avoid planting too many of the same variety to encourage true plant diversity. Different rust fungi only attack specific plant groups: rose rust won’t affect your mint plants, and vice versa.
Sometimes, rust disappears on its own when favourable conditions (moisture, warmth) are no longer present.
How to treat rust?
If your plants are already affected:
- As soon as you notice the first damaged leaves, remove them to limit the spread of this disease.
- Horsetail decoctions are effective when applied fortnightly. You can combine them with nettle manure. These treatments can also be used preventively, as they strengthen your plants and make them more resistant.
- Fungicides help neutralise rust. We recommend using copper-based substances such as Bordeaux mixture, or spraying sulphur.
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