Rusts are recognised as small yellow or orange patches or spots, which appear mainly on the upper surfaces of leaves. Old-fashioned Hollyhocks are particularly susceptible to rust.

On the underside, powdery, raised pustules appear under each spot. This disease can cause leaf fall and seriously weaken plants.

Most rusts attack a specific plant or a small group of related plants and will not transfer from one host to another, but there are varieties for a broad range of plants.

Control:
As a preventative measure it is best to grow rust-resistant varieties of plants whenever possible. As different rusts affect a great many plants, treatment often differs.

Spraying with an approved chemical is effective against most rust fungi. Clear away fallen leaves to prevent a carry-over of the disease.