Identifying Harmful Lima Bean Diseases

The lima bean also known as butter bean is a much loved variety because of its great taste and nourishing properties. The beans have a high content of iron and protein. Basic growing conditions include well-drained soils, average moisture, plenty of sunshine and a warm growing season. Following are some of the diseases you need to watch out for if you cultivate this plant.

Damping Off

This is one of the most common fungal diseases affecting lima beans. Damping off hinders successful germination and causes young seedlings to die. Where temperatures are cool and soils are wet, it becomes difficult for seeds to germinate. The fungi overwhelms the seedlings which end up dying. When planting, use seeds that have been pre-treated with a fungicide. Make sure cool weather has passed before you plant your seeds. Planting in warm weather will encourage successful germination.

Bacterial Blight

This usually develops where humidity is high. Water-soaked spots appear on leaf surfaces. The spots gradually turn brown and are surrounded by a yellow border. As the disease spreads, the spots enlarge to create large dead areas. Where the infection is severe, the leaves appear burned. Wet or greasy areas are also evident on both sides of the leaves which eventually fall off. Symptoms of bacterial blight on pods will include circular, sunken areas that are reddish-brown in color. Seeds get discolored and shrivelled. Avoid overhead irrigation to control humidity. Fungicides that contain copper are also helpful as a control measure. 

Root Rot

It is caused by various fungi in the soil. Small, sunken lesions, reddish-brown in color develop on the roots. The rapidly yellowing leaves finally fall off. Plants become weak and sickly, and eventually die. Root rot also causes stunted growth. Pods remain small with under-sized beans which results in lower yields. Strive to maintain good soil drainage as this is helpful in averting the disease.

Bean Rust

This is a fungal infection that most often develops in cloudy and humid conditions. It is usually evident underneath the leaves but also develops on the bean pods. Bean rust typically manifests as the winter draws to a close and in early spring. Older plants suffer greater affliction. Earliest signs are small, white spots underneath the leaves surrounded by a yellow border. The spots become larger and develop a rust-like color. They gradually spread to the upper side of the leaves, causing leaves to become yellow, dry up and drop. Fungicides are useful as a control measure. Practise crop rotation and control the growth of weeds.

Downy Mildew

This fungal infection usually attacks seeds and seedlings. Infected seeds will not germinate and seedlings fail to grow properly. Leaves develop small, yellow lesions on the upper surface. Spores form underneath the lesions. Pods can also be attacked by the fungal spores, which results in poor quality of seeds. The disease develops most rapidly during cool and wet weather. It is actively disseminated by the wind and rain. Use seed treatments to protect young seedlings from infection. Practice crop rotation as a control measure.