What to do now
Mildest step first.
- Note which leaves are yellow: the oldest at the bottom, the whole plant, or new leaves in a mottled pattern.
- If the soil is soggy, stop watering and let it drain; hold off on nitrogen fertilizer.
- Turn leaves over and look for speckling, webbing, aphids, or spiny yellow larvae.
- Pull out plants with mottled, puckered leaves; mosaic viruses can't be cured.
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Read the pattern
Yellow leaves are a general symptom, so start with where the yellow is. University of Maryland Extension lists drought or waterlogged soil, nutrient shortage, fertilizer burn, diseases, insects and simple aging among the common causes on vegetables. On beans, a few yellow leaves at the bottom of a plant that's still flowering and setting pods is rarely a problem. A whole plant that's pale or yellow-green points to the roots and the soil. A mottled pattern of yellow and green, with puckered or curled leaves, points to a virus. Fine speckling that starts pale and turns yellow or bronze points to spider mites. Orange-brown pustules are bean rust, which has its own page.
Old leaves and normal aging
Maryland notes that older, lower leaves of vegetable plants turn yellow as they age, a process called senescence, while the rest of the plant looks healthy and keeps producing. If only a few bottom leaves are yellow and new growth is green, pull off the yellow ones if you like and keep picking. Iowa State notes that bean plants produce fewer or smaller pods over time, and that frequent harvest keeps them going, since pods left to mature stop new ones from forming. For beans later in the season, sow another row; in Iowa, seed can go in as late as early July for a harvest before frost.
Soggy soil and nitrogen
Beans are legumes and make much of their own nitrogen with root bacteria, but Maryland notes this starts only once a good root system is established; inoculating the seed speeds it up, mainly on ground newly planted in beans. Maryland also explains that roots in poorly drained soil quickly run short of oxygen, leading to wilting, yellowing and browning of leaves, most noticeably in clay soils during long rainy spells. If the soil is soggy, stop watering and let it drain, and next time plant in raised beds or better-drained ground. Iowa State adds that cold, wet soil is a common cause of poor stands, so wait for warm soil to plant. Go easy with fertilizer: Maryland says excess nitrogen delays flowering and beans is usually not necessary. Plants in well-drained soil that stay pale for weeks may have a true shortage; see the nitrogen page for how it looks.
Mosaic viruses
Bean common mosaic and bean yellow mosaic viruses cause yellow that's patchy rather than even. Washington State University describes blue-green, green or yellowish mottling, leaves that curl down or cup, unusually glossy and brittle leaves, and deformed pods, and University of Minnesota Extension adds that infected plants are stunted. Both viruses are spread by aphids, and bean common mosaic also travels in seed, so don't save seed from plants with symptoms. WSU suggests resistant varieties such as 'Goldrush', 'Oregon 91G' and 'Roma II', and advises against planting beans near clover or gladiolus, which can carry bean yellow mosaic. No spray cures a virus; Iowa State advises removing infected plants promptly and controlling aphids.
Mites, aphids and beetles
Spider mites cause fine speckling that turns yellow and eventually bronze, often in hot, dry weather, Iowa State says, and severe infestations make leaves drop. Look for tiny moving dots and fine webbing on leaf undersides. Keep the soil evenly moist, wash the leaves with water, and use insecticidal soap if needed. Aphids, leafhoppers and fleahoppers suck sap and can leave leaves curled, yellowed or distorted, sometimes sticky with ; a strong water spray knocks them off. Mexican bean beetles feed from the undersides and leave a lacy skeleton that dries tan and can look like yellowing from a distance. Turn leaves over for the spiny yellow larvae and yellow egg clusters, and crush or hand-pick them.
Read the whole label first: it must list your crop, and its directions (amount, timing, gear, bees, days before harvest) are the law. If this page and the label differ, follow the label.
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- Nitrogen DeficiencyUniform yellowing starting on the oldest, lowest leaves while new growth stays green — nitrogen is being pulled from old tissue to feed new growth.
- Spider MiteStippled, bronzed leaves with fine webbing on undersides; damage intensifies in hot, dry weather.
- Mexican Bean BeetleLacy skeletonized bean leaves with yellow-spotted oval beetles and spiny larvae on undersides.
- AphidSoft, clustered insects on new growth causing curled leaves and sticky honeydew.
- Why do my bean leaves have rust-colored spots?Rust-colored or orange-brown pustules on bean leaves are bean rust, a fungal disease that spreads in warm, humid conditions and is manageable but rarely fully eliminated once established.
- My pole bean plants are lush and green but I'm getting very few beans — why?Pole beans often drop flowers and fail to set pods when temperatures climb above about 85°F or when given too much nitrogen — excess leafy growth at the expense of production.