Rusts are a collection of fungal diseases that thrive in high humidity, which discolour leaves and encourage them to drop prematurely. A wide range of plants may be affected, including trees, shrubs, perennials, annuals, bulbous plants, vegetables, fruits and indoor plants. The rusts are composed of small brown, yellow or orange pustules that cover leaves, which then die off. Stems may also be affected, becoming extensively distorted and eventually rupturing.

Control

Hygiene is the best way to prevent rust; always make sure that all fallen leaves are removed from the top of the soil before they begin to decompose. Prune plants to ensure a free circulation of air, especially at the centre. Any infected leaves should be burned immediately, and affected plants should be isolated to prevent spores from spreading.

Plants should be sprayed with a fungicide such as such as propiconazole or mancozeb in spring before the overwintering spores have chance to germinate.