How to recognise it
In the summer, pustules are produced on any above ground plant part. They are commonly spotted first on the underside of leaves, usually accompanied by a discolouration of the leaf around the pustule and on the top surface of the leaf. The pustules are often dark brown (hence the name ‘rust’) with yellow discolouration, although other colour combinations are possible. Later in the season black or very dark coloured pustules may appear.
Why it’s a problem
Rusts generally weaken plants, draining nutrients from them without killing them (except in extreme cases). It is also unsightly.
Where you are likely to find it
Rust can be found on a wide variety of plants including trees, shrubs, soft fruits, vegetables and ornamental herbaceous plants.
How to prevent it
How to get rid of it
A few fungicides are effective in controlling rusts, although their use is often limited to ornamental plants.
Avoid excessive use of nitrogen rich fertilisers, which can aggravate a rust problem.
Badly affected plants should be dug up and destroyed (eg burned), not placed on a garden compost heap. The extent to which this drastic action is required depends on the type of rust affecting the plant and the severity of the attack.
Is it good for anything?!
Other useful information
There are many different types of rust, each of which having their own ‘target’ plants and symptoms. We have further details about: