Chocolate Spot
Disease · Commonly affects: Broad beans, Field beans, Faba beans, Vetches, Winter beans
Chocolate spot is a fungal disease chiefly affecting broad beans. Small reddish-brown marks are common in damp weather, but the disease becomes far more damaging when plants are crowded, stressed or overfed. It is a familiar UK allotment problem because wet springs and dense rows allow the infection to spread quickly through foliage and pods.
How to identify it
Early symptoms are small, chocolate-brown or reddish-brown spots, often 1-5 mm across, on leaves, stems and pods. They may remain separate in light infections. In severe attacks, spots merge into large dark patches, foliage becomes grey-brown and stems may show long streaks. Affected leaves can wither and fall. Look closely inside dense lower growth after prolonged damp weather, where poor airflow keeps leaves wet and symptoms usually start first.
Damage
Mild chocolate spot is largely cosmetic, but severe disease reduces leaf area and weakens plants. Flowers may abort, pods set poorly and developing beans can be marked or shrivelled. In very wet, crowded crops, stems may die back and whole plants can collapse. Crop quality and yield are most affected when infection begins before or during flowering.
Prevention
Sow broad beans at sensible spacings and avoid overcrowding rows, particularly with autumn-sown plants. Choose an open, sunny site with good airflow, and avoid sheltered corners where foliage stays wet. Do not overfeed with nitrogen-rich fertiliser, which encourages soft, dense growth. Water the soil rather than leaves and remove weeds that block ventilation. Use a crop rotation, clear old bean debris after harvest and choose robust varieties suited to your local sowing season.
How to manage it
At the first signs, pick off badly spotted leaves where this will not strip the plant bare, and remove heavily affected plants if infection is spreading rapidly. Bin the material or use municipal green-waste collection rather than home composting. Thin congested growth and keep weeds down to improve airflow. Harvest pods promptly, especially in damp weather. After cropping, remove all plant residues and do not grow broad beans in the same ground for several years if serious outbreaks recur.
Chocolate Spot: frequently asked questions
How do I identify chocolate spot?
Early symptoms are small, chocolate-brown or reddish-brown spots, often 1-5 mm across, on leaves, stems and pods.
How do I prevent chocolate spot?
Sow broad beans at sensible spacings and avoid overcrowding rows, particularly with autumn-sown plants.
How do I get rid of chocolate spot?
At the first signs, pick off badly spotted leaves where this will not strip the plant bare, and remove heavily affected plants if infection is spreading rapidly.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.