Broad Beans: Pests & Diseases
Broad beans are hardy, generous plants that suit early and autumn sowing in many parts of the UK. Their upright stems need a sunny, reasonably sheltered site and firm soil. They can produce a heavy crop with little fuss, but close attention to the flowering period helps prevent blackfly taking hold.
Common pests
Black bean aphid, often called blackfly, can blanket soft shoot tips and flower stems in late spring. Pea and bean weevil leaves characteristic notches around young leaf edges. Mice can eat freshly sown beans or excavate rows before germination. Slugs may damage seedlings, and pigeons occasionally pull up young plants. Aphid colonies can also attract ants, which feed on honeydew and may hinder natural predators.
Common diseases
Chocolate spot produces reddish-brown to chocolate-coloured spots on leaves, stems and pods; it is worst in damp, crowded crops. Broad bean rust forms rusty orange-brown pustules, often later in the season. Foot rot and root rots cause weak growth, yellowing and collapse from damaged roots or stem bases, particularly in cold, wet ground. Viruses may cause mottling or distortion and are often associated with sap-feeding aphids.
Prevention
Grow broad beans in an open position with enough room for good airflow, as this greatly reduces chocolate spot and rust. Rotate legumes between beds and avoid sowing into waterlogged soil. Select robust varieties suited to local conditions, and keep rows weed-free without damaging shallow roots. Use cloches over newly sown seed if mice are known to be troublesome, and clear diseased foliage and old stems from the plot after harvest.
Non-chemical control
As soon as the lowest flowers have set, pinch out the soft growing tips to remove the blackfly's preferred feeding site. Squash or wash off small aphid colonies with a firm spray of water, and retain ladybirds, hoverfly larvae and lacewings. Hand-pick weevils when practical. Use cloches to protect seed from mice and inspect damp hiding places for slugs. Remove badly spotted leaves to improve airflow, disposing of them away from healthy crops.
What to look for
Check seedlings for missing beans, slug grazing and weevil notches. From bud formation until pods set, inspect shoot tips twice weekly for blackfly, especially in warm, still weather. After rain or during humid periods, look through the crop for brown chocolate spot lesions, rust pustules, wilting plants and poor airflow between stems.
Tips
Support tall varieties with string around corner stakes before they lean in wind. Pick pods while beans are still tender, but leave a few lower pods to mature if saving seed from healthy plants. Water only at the base when conditions are dry.
Broad Beans pests & diseases: frequently asked questions
What are the common pests of broad beans?
Black bean aphid, often called blackfly, can blanket soft shoot tips and flower stems in late spring.
What diseases affect broad beans?
Chocolate spot produces reddish-brown to chocolate-coloured spots on leaves, stems and pods; it is worst in damp, crowded crops.
How do I prevent pests and diseases on broad beans?
Grow broad beans in an open position with enough room for good airflow, as this greatly reduces chocolate spot and rust.
General guidance for UK home gardens, focused on prevention and non-chemical control. The RHS or a local garden centre can help with tricky cases. Page updated 18 Sep 2026.