Yellow Leaves on Pole Beans

Function

• Yellow leaves on pole beans are indicators of disease.

Types

• Diseases that may cause yellowing of pole bean leaves include root rot, bean mosaic diseases, and bean rust. Bacterial blight does not cause wholesale yellowing, but parts of the leaves will turn yellow.

Identification

• Pale and/or yellow leaves may indicate root rot. Additional identification can be made by looking at the roots of the plant in question. Pole beans afflicted by root rot have brown, mushy roots. Healthy plants have firm, white roots. Bean mosaic diseases cause pole beans to be stunted. Bean pods will be few, if any appear at all. Pole bean plants themselves will have leaves that are oddly shaped, with yellow splotching. Bean rust affected pole beans have leaves that are yellow on tops with a brown flakiness on the underside that rubs off on fingers if it is touched. Bacterial blight creates big brown spots on the leaves that are tinged with yellow rings around their edges.

Effects

• In addition to being unsightly, all of these diseases result in unhealthy plants with low production rates and sometimes death. Diseased plants themselves may spread disease to other plants in the bean family. Diseases that afflict pole beans afflict all other members of the bean family as well.

Prevention/Solution

• All the diseases mentioned above can best be prevented by planting disease-resistant varieties of pole beans. Additionally, diseases can be avoided by watering the soil, not the plants themselves. Exposing pole bean foliage to excessively damp conditions encourages disease. Control of insects (such as aphids) that can spread disease from one infected pole bean plant to another should also be enacted through the use of conventional or organic pesticides. Finally, crop rotation schedules that allow at least three years between plantings of bean crops in a single area keep disease risk to a minimum. As most pole bean diseases are fungal, they may be able to be controlled by use of fungicides if caught early on.