Orange Fungus on a Plant

Written by tyler lacoma
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Orange Fungus on a Plant
Orange fungus can be either rust, slime moulds, or a mushroom growth on a plant. (orange ball growth image by Dave from

Gardeners never like to see a fungus on a plant, but there are many different types of fungus and their presence can mean different things depending on the type of fungus and the plant it is infesting. Typically, orange fungi are relegated to wet climates with fairly mild winters, which allow the fungus to infect a plant and spread more easily. Such fungi are dangerous to the health of the plant and should be removed as soon as possible.

Orange Rust

Orange rust is a type of fungus that infects broadleaved plants, and is the most common type of orange fungus. It is often called, simply, rust, and is prevalent in areas like the northwest U.S. This fungus appears to be a layer of rust-like fuzz or grit spreading on the leaves of plants. It may produce small shoots to create more spores. Rust may also grow on the underside of leaves and the trunks of trees.


Ganoderma is a type of mushroom that likes to grow at the roots or branches of trees, and can also look like an orange fungus spreading across the bark. This fungus usually inhabits trees that are damaged in some way, and prefers a wet climate. It can be found on many trees, prefers decaying wood. Several types of ganoderma exist, with a wide range of colours, including orange.


Rust will not immediately kill a plant, but the fungus does quickly weaken the plant it grows on. Shoots infected with rust are unlikely to produce new leaves, and plants with rust problems will probably not flower. As the fungus spreads the leaves yellow and die, and the entire plant weakens. Any new growth is likely to be weak and easily destroyed. If the fungus grows enough, it can kill the plant. Ganoderma, including the orange kind, is a symptom of rot and means there are usually permanent problems with the tree, especially when they grow near roots.


If a plant is infected with rust, it should be removed from other plants in the area immediately. If only a small section is infected, growers can cut that section off and dispose of it. Rust should never be mixed in with compost or any type of fertiliser. A fungicide can help protect nearby plants from infection. Ganoderma is probably a permanent condition, but growers can dress any wounds of nearby trees to keep the mushroom from spreading.

Slime Molds

Slime moulds are funguslike growth that occur in wet climates and are often found in the bark of trees or in grass and soil. They tend to be bright colours like white or orange, but they are not necessarily harmful. Slime moulds rarely feed on plants themselves, preferring to eat bacteria that grow in wet areas. Most slime moulds eventually dry out and die as the seasons change.

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