Chocolate spot is a fungal disease that affects broad beans and a wide range of other plants. , and is seen as; dark, chocolate-coloured spots on all parts of the plant.
It is caused by either of two fungi;
Botrytis fabae; the most common, only affects broad beans.
The disease is generally seen in mid-spring on early spring-sown broad beans.
Note; the disease does not affect runner and French beans.
Botrytis cinerea causes similar symptoms, and may also cause grey mould to form on a wide range of plants.
Once established; the fungus produces air-borne spores, particularly under wet conditions, and it these spores that spread the disease.
Small round, red-brown spots appear on all parts of the plant, and in severe cases leaves shrivel and plants can collapse.
Note; Under dry conditions the spots are usually much smaller.
Control;
Avoid cool, damp, overcrowded conditions, and ensure that there is good ventilation in the vicinity of the plants.
Note; Destroy and clear away any affected plants or plant debris.