Identifying and Treating Broad Bean Diseases

Broad beans are easy-to-grow crops, often recommended for amateur, first-time household gardeners. They need little seasonal maintenance and moderate soil nutrition. If you grow them, you need to know how to identify the common diseases and how to treat them. Most broad bean diseases can be easily identified.

TIP: Our expert gardening advisor, Susan Patterson suggests, "Always leave plenty of room between plants for air circulation."

Disease 1: Broad Bean Chocolate Spot

This is a serious disease of the plant foliage. It is caused by the Botrytis fungus. The fungus growth becomes more apparent during humid conditions. It is also called grey molding of the broad beans.

TIP: Susan notes, "Chocolate spot is more of a problem with fall crops than spring crops."

Chocolate Spot Symptoms

Typical signs of Chocolate spot disease include the presence of rounded, reddish-brown spots on the leaves. Sometimes, the spots may appear on the pods and stems. If the disease spreads to the main stem, the spots develop a brownish-black appearance. The leaves are often covered with a characteristic, thread-like covering, creating the impression of a mould. The seasonal bloom is delayed and the flowers develop a weathered appearance. Even the older pods, containing the seeds, can be infected by spotting disease. The disease often begins during the mid-winter season, which is uncommon for most fungal infections.

Chocolate Spot Disease Control

Ensure that the soil is always well drained, particularly during the rainy season. You can raise the vegetable bed to ensure sustained draining of excess water. Leaves showing a clustered appearance with any form of molding should be pruned-off. Always dip your pruning gear in a multi-purpose fungicide before pruning. This helps to avoid spreading the infection to the foliage around the pruned sites. The soil should be periodically enriched with doses of potash and potassium-rich fertilizers. A good idea is to start increasing the potash content in the fertilizer-mix with the onset of the winter season. Clustered foliage can lead to faster spreading of Chocolate spot in the garden bed. Always maintain a 50-cm gap between the plant rows. Prune repeatedly before the spring season to ensure well-spaced growth.

Disease 2: Broad Bean Rust

This is the only known disease can that quickly infest an entire broad bean crop. Rust is caused by the Uromyces fungus. Its identification and control is very difficult. It is known to undergo repeated dormant stages and re-surface throughout a crop’s cycle.

Broad Bean Rust Symptoms

It is critical that you are able to identify the initial signs of rusting because it spreads very quickly. The typical, rusting indications include the development of yellow spots on the underside of leaves. Some spots may have a powdery, outer surface that is easy-to-detect. Remember, rusting spots can develop beyond the usual seasonal patterns, unlike most fungal infections. Hence, you should check your broad bean crop for rusting symptoms even during the dry season.

Broad Bean Rust Control

Chemical treatment is not effective to contain this disease. Timely identification of the diseased plant and its systematic destruction is the only solution. You should continuously check for rusting symptoms and prune-off the infected foliage. Never use the pruned-off, infected parts for composting or any gardening activity. You can use a combination of fish oil and sulphur dust to spray the plants. This helps to contain the spread of rust disease by killing young, fungal spores.