Bean Chocolate Spot
Botrytis fabae
Bean Chocolate Spot
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Chocolate Spot is a fungal leaf spot disease that in serious infections can cause the death of vital parts of the plants. It is often caused by growing beans in overcrowded areas that have poor lighting and drainage. Plants that infected in early Spring often recover if treated.
Identification
Dark chocolate brown spots mainly on the upper surface of the leaves, leaf stalks, pods, seed coats and flowers. Elongated brown lesions can appear also on the stems of the plant. Spots can merge together to cause the death of larger areas of the plant.
Growth factors
Favours damp, shaded conditions that have poor airflow.
Symptoms
Chocolate brown spots on leaves, flowers, pods, seed coat and stems.
Biological treatment
Apply a potash fertilizer, improve drainage, and increase the spacing between plants and rows.
Chemical treatment
There are some approved chemical fungicides that are effective against the fungus although the application is rarely necessary.
Lifecycle
Most attacks start from the disease overwintering in old plant debris and infect the new hosts via their leaves.
Prevention
Having good airflow through the plants. Growing the beans in full sun.