broad bean rust

Symptoms

Bright orange-brown raised pustules (uredinia) on leaf undersides + stems, yellow chlorotic halos around pustules on upper leaf surface, severe infection causes premature leaf drop, dark teliospore pustules form late in season on dying tissue.

Plants affected

• broad bean / fava bean

Easily confused with

• chocolate spot of broad bean

  How to tell them apart: Chocolate spot (Botrytis fabae) starts as small reddish-brown to chocolate-coloured spots scattered on leaves, stems and pods; the spots stay flat and superficial, and in wet weather coalesce into large dark-brown to greyish blotches with a grey mouldy bloom, eventually killing whole leaves. Broad bean rust (Uromyces viciae-fabae) instead forms slightly raised, powdery pustules: early creamy-yellow flecks become rusty cinnamon-brown uredinia mainly on the lower leaf surface that rupture and release dusty spores onto your finger, later turning into dark brown to black teliospore pustules. Key test: rub the lesion — rust powders off as coloured dust and feels raised, while chocolate spot is a flat dry stain with no spore powder (only grey fuzzy mould when sporulating).

Common questions

How do I recognise broad bean rust on broad bean / fava bean?

Bright orange-brown raised pustules (uredinia) on leaf undersides + stems, yellow chlorotic halos around pustules on upper leaf surface, severe infection causes premature leaf drop, dark teliospore pustules form late in season on dying tissue.

Do I have to report broad bean rust?

No. broad bean rust is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is broad bean rust treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.