Green beans (Phaseolus vulgaris), often called snap beans, are a nutritious addition to your home garden. Green bean leaf curl may be caused by a viral disease or by a pest infestation. Fortunately, you can prevent many problems with proper care, and prompt treatment may save your green beans and the other vegetables in your garden.
If your runner bean leaves are curling, it may be caused by a viral infection. While not common, the cucurbit leaf crumple virus can infect green beans and can cause curling and crumpling of leaves. Other symptoms include yellow leaves and stunted growth.
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Two more common infections with similar symptoms are bean common mosaic virus and bean yellow mosaic virus. This virus can cause the leaves to curl downward. Other symptoms include yellow and green mottled leaves, elongated leaves and stunted plant growth. The bean pods may also become curled and may fail to reach full size. Infection late in the season may not reduce your harvest.
Mosaic viruses are transmitted to plants by aphids, and the cucurbit leaf crumple virus is transmitted by whiteflies, so make sure you control pests, select green bean varieties that are resistant to these viruses and never plant seeds from an infected plant.
Bush Bean Pests
Aphids and whiteflies can not only transmit diseases but a serious infestation alone can cause problems for your bean plants. Aphids are small pests that are usually green or yellow in color. You will see them on the stems and the underside of the leaves. Symptoms of these pests include distorted leaves, yellowing and stunted shoot growth.
Whiteflies are small white pests that are similar to aphids. They are also found on the underside of the leaves and can cause leaves to curl, yellow and dry out.
For a lighter infestation of these pests, pruning affected stems and leaves or spraying the pests off the plant is often effective. You can also use reflective mulch to discourage aphids and whiteflies. Insecticidal sprays may be needed for heavier infestations, but this is a last resort since it can harm beneficial insects. Check the insecticide label and ensure it is safe for use on bean plants.
Prevent Green Bean Leaf Curl
Healthy plants that are receiving proper care are less prone to succumbing to disease and pests. Green beans are warm-season vegetables. Wait until all danger of frost has passed before planting seeds in your garden. There are many varieties of bean plants from which to choose. Pole bean varieties will need a trellis or support, while bush bean varieties can grow without support.
Plant beans in full sun and well-drained soil. Water the plants regularly to maintain soil moisture and avoid getting the leaves wet when irrigating, as this can increase the chances of a fungal infection. Carefully control weeds around the plants, taking care not to damage the plants' roots. Avoid spraying herbicides, as any stray mist that hits your bean plant may cause the leaves to curl.
- Alabama Cooperative Extension System: Common Diseases of Snap and Lima Beans
- University of Georgia: Cucurbit Leaf Crumple Virus Detected on Snap Beans at UGA, Tifton
- PlantVillage: Bean
- University of California Statewide Integrated Pest Management Program: Whiteflies
- University of California: Curling Leaves on Plants
- Clemson University Cooperative Extension Service: Bush & Pole-Type Snap Beans
- Cornell University Vegetable MD Online: Virus Diseases of Snap and Dry Beans