Pole beans make a great addition to any garden as they are easy to grow, don't require a lot of space, unless you plan on canning, and provide a plentiful harvest. Gardeners appreciate the lush, green foliage that pole beans offer; however, when yellow leaves appear, one should act quickly to determine the cause and treat accordingly. Yellow leaves on pole beans do not necessarily mean the beans are dying, but without prompt attention could render unfavorable results in bean production and death of the plant.
Determine whether your pole beans have received an over-abundance of rain. This can be natural rain or from watering. While you cannot control Mother Nature, if over-watering seems to be an issue, there are ways you can help.
Limit watering to allow the ground to dry out through the first inch of topsoil between each watering.
Discontinue use of timed sprinklers. Timed sprinklers are ideal during periods of drought.
Watch the forecast for your area so you will get a better idea of when to water. When watering, do it in the early morning before full sun or late in the evening after the sun has gone down. The evening time will allow for more moisture to be absorbed by the plant.
Check bean pods for signs of water spots. In addition to yellow leaves, some leaves may contain brown spots as well. Bacterial blight can occur from seed affected with the disease, bean debris left in the garden near bean plants and wet bean plants.
Select disease-free seed and avoid harvesting and saving seed from plants suspected of bacterial blight.
Remove bean debris from the garden. Bean debris can be recycled into a compost bin unless the debris is from unhealthy plants.
Remove all debris from contaminated plants, bag and dispose. Contaminated debris can also be burnt to avoid re-infestation.
Bean Mosaic Virus
Observe pole bean leaves for yellowing, yellowish-green or mottled yellow. Leaves may also be shaped irregularly. Plants mature enough for pods may produce little or no pods. Bean mosaic virus is transferred to beans via aphids that have picked up the virus from other plants such as red or white clover.
Limit bean mosaic virus from your garden by planting a variety of bean that is resistant to the disease.
Avoid planting pole beans near fields planted with alfalfa or clover crops, as recommended by the University of California Agriculture Integrated Pest Management.
Apply insecticide regularly to avoid or limit the presence of aphids which carry the virus from plant to plant.