Q What is it?

A Broad beans are often attacked by a rust (Uromyces fabae) which covers the leaves with tiny yellow spots. Red-brown powdery spots develop later on the underside of leaves, and stems and pods can be affected.

Caption: Red-brown spots appear on the leaf undersides later on

Q Is it serious?

A Usually it develops too late to affect the yield of beans. However, late-sown spring beans can suffer badly in July, when the warm days and dewy nights favour the disease. There are no chemical controls available to gardeners.

Picking off and destroying infected leaves may slow the disease down. Tiny mites often feed on the spores in the pustules – these mites are harmless.