The cultivation of broad beans, also called beans or beans, has been practiced since ancient times and has become a valuable food source in many cultures around the world. These versatile legumes are not only delicious, but also offer a host of nutritional and environmental benefits that make them a smart choice for any garden.
Although it is considered a hardy plant, there are also bean diseases that reduce production and can kill the plant. In its time, we have already published about the black bean aphid, but in conditions of high environmental humidity, it also copes with generic fungi such as mildew, botrytis and bacteriosis.
Main broad bean diseases
Bacterial brown spot (Pseudomonas syringae)
Cause: bacteria
Symptoms
Small dark brown necrotic spots on leaves which may be surrounded by an area of yellow tissue; waterlogged spots on pods turning brown and necrotic; pods may twist and deform in the area of infection
The bacterium overwinters in crop residues; disease more severe when foliage is wet for prolonged periods
disease management
Plant only certified seeds; rotate crops regularly; remove crop debris from the field after harvest
Botrytis (Botrytis fabae)
Cause: mushroom
Symptoms
Symptoms of the disease can be aggressive or non-aggressive; Non-aggressive chocolate spot symptoms are small reddish-brown lesions on the plant’s leaves that may also be present on the stems and pods; in conditions of high humidity, the disease goes into the aggressive stage, and the lesions coalesce and become covered with spongy mycelium; large patches of tissue can become necrotic and die.
Situation
Long periods of high humidity favor the transition from the non-aggressive phase to the aggressive phase; the aggressive phase of the disease promotes low levels of potassium and phosphorus in the soil and overcrowded plants
disease management
Control should aim to prevent the aggressive stage of the disease which can be reached by lowering the humidity; use proper plant spacing to promote air circulation around the plants; Foliar fungicide applications throughout the season will protect the crop from botrytis spot.
mildew Peronospora viciae
Cause: mushroom
Symptoms
Yellow-brown spots on the upper side of the leaves; Angular greyish-white spongy fungal patches on undersides of leaves; plant growth may be stunted or distorted and the entire plant may die before flowering; the plant can produce
Situation
The fungus overwinters in soil and crop debris; the fungus can survive in the soil for 10-15 years
disease management
Crop rotation for at least 5 years; deep down to the remains of the crop; Avoid planting deeper in the ground in late fall as this can promote serious infections.
Fusarium root rot Fusarium solani
Cause: mushroom
Symptoms
Stunted plant growth; basal leaves yellowish and necrotic; reddish-brown or black streaks on roots that coalesce as they mature; lesions may extend above ground
Situation
Damage from disease onset is aggravated by hot, compacted soils, limited soil moisture and low soil fertility.
disease management
Control is based on cultural practices, eg no cross planting in the same area more than once in a 5 year period; treat seeds with an appropriate fungicide before planting-
powdery mildew (erysiphe pisi)
Cause: mushroom
Symptoms
Yellow spots on the upper side of the leaves; grayish-white powdery areas merging to cover entire plant; if the plant is heavily infected, it may appear light blue or gray in color
Situation
The fungus overwinters in plant debris or an alternate host; disease emergence is favored by hot, dry weather with cool nights that lead to dew formation
disease management
Plant resistant varieties, especially if planted late; use overhead irrigation (removes fungus from leaves and reduces viability). Anticipate the planting of the broad bean crop. Frequent applications of sulfur may be necessary to control severe infestations.
Leaf blight (Xanthomonas campestris syn. Xanthomonas axonopodis)
Cause: bacterium
Symptoms
Watery spots on leaves that enlarge and become necrotic; the spots may be surrounded by an area of yellow coloration; the lesions coalesce and give the plant a burnt appearance; leaves that die remain attached to the plant; circular, sunken, reddish-brown lesions may be present on pods; pod lesions may ooze in wet conditions
Situation
The disease can be introduced through contaminated seeds; bacteria overwinter in crop debris; disease emergence favored by warm temperatures; spread is greatest in damp and wet weather
disease management
Plant only certified seeds and choose plant-resistant varieties. Treat seeds with an appropriate antibiotic before planting to kill bacteria. Spray plants with an appropriate copper protectant fungicide before symptoms appear.
Bean rust (Uromyces viciae-fabae)
Cause: mushroom
Symptoms
Broad bean rust is one of the most common fungal diseases of broad bean leaves. The fungus causes small dark brown powdery spots surrounded by a pale yellow halo on leaves and stems.
On leaves and stems: small dark brown powdery spots, often surrounded by a pale yellow halo.
disease management
- Maximize airflow around plants by spacing them wider and avoid damp, damp sites
- Destroy infected plant material, as spores produced late in the season can survive in a semi-dormant state on crop residues and seeds.