The Green Bean Plants Are Yellow and Losing Leaves

Rust

• Rust is a fungal disease that infects the foliage and pods of green beans. Symptoms of infection consist of premature leaf yellowing, premature leaf drop and fungal growth on bean pods. The fungus favors cool, wet weather conditions with temperatures ranging from 60 to 75 degrees Fahrenheit. Infections are more severe on weakened or stunted plants. The fungus overwinters on infected plant tissue, which can cause perennial infection. Apply fungicides as soon as symptoms appear, and destroy infected plant tissue to control the disease.

Bacterial Blight

• Two types of bacteria, Xanthomonas campestris and Pseudomonas syringae, cause bacterial blight on green bean plants -- both appear with similar symptoms. Symptoms of infection consist of brown spots surrounded by a yellow halo on foliage, leaf yellowing and browning, burned appearance on foliage and premature leaf drop. The disease causes brown spots on bean pods, distorted pod growth and poor fruit production. One disease favors temperatures between 85 to 95 degrees Fahrenheit, while the other favors cooler temperatures. Avoid planting infected seeds and avoid overhead irrigation to prevent infection. Apply copper-based fungicides to control the disease.

Powdery Mildew

• This common fungal disease affects a variety of vegetable crops, including green beans. As the name denotes, the fungus covers infected plant tissue with a white powdery coating. The disease causes curled foliage, poor leaf growth, premature leaf yellowing and leaf drop. The fungus favors moisture on leaf surfaces and windy weather for infection spread. Apply fungicides as soon as symptoms are present to reduce the severity of the disease.

Rhizoctonia Root Rot

• Rhizoctonia root rot is a soil-borne disease that affects the roots of green bean plants and produces aboveground symptoms. Symptoms of infection consist of seedlings damping off, premature leaf yellowing, premature leaf drop, stunted plant growth and stem lesions. This root rot fungus favors cool weather conditions for infection. Plant fungicide-sprayed seeds to avoid Rhizoctonia root rot infections. Avoid planting in soil where previous infections occurred to reduce the chances of new infections.