01Yellowing leaves
| Possible cause | Clemson |
|---|---|
| Bean root rot | Clemson Cooperative Extension says the plant's roots die off and the leaves turn yellow. Source: Bean & Southern Pea Diseases · checked 2026-09-27 |
| Spider mites | Clemson Cooperative Extension says when only a few mites are present, leaves show faint whitish speckling, but a heavy infestation turns the leaves pale yellow or bronze and dries them up. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 |
02Spots on leaves
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Halo blight | Clemson Cooperative Extension says leaves show light greenish-yellow rings around a brown spot, and with age the spots run together as the leaf turns yellow. Source: Bean & Southern Pea Diseases · checked 2026-09-27 | Colorado State University Extension says the water-soaked leaf spots develop a greenish-yellow ring, or halo, that forms from a bacterial toxin. Source: Bacterial Diseases of Beans · checked 2026-09-27 |
| Common bacterial blight | Clemson Cooperative Extension says leaves with common blight turn brown and drop from the plant quickly. Source: Bean & Southern Pea Diseases · checked 2026-09-27 | Colorado State University Extension says leaves get a scalded look, with water-soaked spots scattered through the tissue. Source: Bacterial Diseases of Beans · checked 2026-09-27 |
| Cercospora leaf spot | Clemson Cooperative Extension says irregular, tan spots show up mostly on the lower leaves, and a bad attack causes heavy leaf drop and stunts the plant. Source: Bean & Southern Pea Diseases · checked 2026-09-27 | No matching line in the Colorado State pages we checked. |
| Mosaic virus | Clemson Cooperative Extension says infected leaves show sharply defined patches of odd coloration, a mottled or blotchy look often called mosaic. Source: Bean & Southern Pea Diseases · checked 2026-09-27 | No matching line in the Colorado State pages we checked. |
03Curled or distorted leaves
| Possible cause | Clemson |
|---|---|
| Powdery mildew | Clemson Cooperative Extension says new growth looks twisted, curled, or dwarfed and can turn yellow and drop, and pods can end up dwarfed and misshapen too. Source: Bean & Southern Pea Diseases · checked 2026-09-27 |
04White or powdery coating
| Possible cause | Clemson |
|---|---|
| Powdery mildew | Clemson Cooperative Extension says leaves get patches of a whitish to grayish powdery growth on them. Source: Bean & Southern Pea Diseases · checked 2026-09-27 |
05Holes and chewed leaves
| Possible cause | Clemson | Wisconsin |
|---|---|---|
| Mexican bean beetle | Clemson Cooperative Extension says the larvae eat out sections of leaf tissue between the veins, leaving the leaf with a skeletonized, lacy look. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 | No matching line in the Wisconsin pages we checked. |
| Bean leaf beetle | Clemson Cooperative Extension says bean leaf beetles cause two kinds of damage: girdling stems near the soil line, and large, irregular holes chewed in the leaves. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 | University of Wisconsin–Madison Extension says adult bean leaf beetles chew small holes in the leaves while feeding from the underside of the leaf. Source: Bean Leaf Beetle · checked 2026-09-27 |
06Insects you can see
| Possible cause | Clemson | Wisconsin |
|---|---|---|
| Aphid colonies | Clemson Cooperative Extension says aphids are small, soft-bodied insects roughly 1/16 to 1/8 inch long, usually green but sometimes yellow, pink, brown, or black. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 Clemson Cooperative Extension says aphid colonies are most common during cool, dry weather on small plants. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 | No matching line in the Wisconsin pages we checked. |
| Spider mites | Clemson Cooperative Extension says spider mites are tiny, eight-legged pests more closely related to spiders than to true insects. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 Clemson Cooperative Extension says on the plant, spider mites show up as tiny specks on the undersides of leaves, where they pierce the leaf and feed on sap. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 Clemson Cooperative Extension says the undersides of the leaves usually get covered with fine silken webs that the mites crawl over. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 | No matching line in the Wisconsin pages we checked. |
| Mexican bean beetle | Clemson Cooperative Extension says adult Mexican bean beetles are very convex and yellow to coppery-brown, with eight small black spots making three rows on each wing cover. Source: Bean & Southern Pea Insect Pests · checked 2026-09-27 | No matching line in the Wisconsin pages we checked. |
| Bean leaf beetle | No matching line in the Clemson pages we checked. | University of Wisconsin–Madison Extension says adult bean leaf beetles are about a quarter inch long, colored yellow-green to red, with four black spots on their backs. Source: Bean Leaf Beetle · checked 2026-09-27 |
07Wilting or dying back
| Possible cause | Clemson | Colorado State |
|---|---|---|
| Bacterial wilt | No matching line in the Clemson pages we checked. | Colorado State University Extension says on older plants, leaves wilt, most often when it's warm and the plant is short on moisture. Source: Bacterial Diseases of Beans · checked 2026-09-27 |
| Rust | Clemson Cooperative Extension says rust makes rust-colored spots on the undersides of leaves, and when the attack is severe those leaves turn yellow, wilt, and drop off the plant. Source: Bean & Southern Pea Diseases · checked 2026-09-27 | No matching line in the Colorado State pages we checked. |
08Stems and canes
| Possible cause | Clemson |
|---|---|
| Watery soft rot | Clemson Cooperative Extension says the watery spots grow quickly in cool, damp conditions and run together, girdling the stem. Source: Bean & Southern Pea Diseases · checked 2026-09-27 |
09Fruit, pods and tubers
| Possible cause | Clemson |
|---|---|
| Watery soft rot | Clemson Cooperative Extension says infected pods turn into a soft, watery mass, then die back and turn brown, and the affected spots soon get covered with a white fungal growth. Source: Bean & Southern Pea Diseases · checked 2026-09-27 |
What to do about it. This site only covers how to recognize a problem. For what to do next, open the Extension page linked in the row: their advice is written for their region and is kept up to date by them.
Pages compared on this chart
- Bean & Southern Pea Diseases, Clemson Cooperative Extension (checked 2026-09-27)
- Bacterial Diseases of Beans, Colorado State University Extension (checked 2026-09-27)
- Bean & Southern Pea Insect Pests, Clemson Cooperative Extension (checked 2026-09-27)
- Bean Leaf Beetle, University of Wisconsin–Madison Extension (checked 2026-09-27)