Green beans (Phaseolus vulgaris), commonly referred to as snap beans, make nutritious, edible gardening possible even in small spaces. Though these versatile vegetables require only moderate care, examine them regularly for any problems or signs of ill health. If you notice curling green bean leaves, this may signal viral problems that require prompt attention and changes in your landscape.
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Proper planting and regular maintenance for this warm-season crop increase the likelihood of avoiding disease problems or recovering quickly if they hit. Plant green beans during late spring or early summer when temperatures range from 60 to 75 degrees Fahrenheit. Grow snap beans in areas that provide full sun exposure for optimal growth. Green beans thrive in most soil types provided that soil is well-drained and high in organic content. Maintain a soil pH level of 5.8 to 6.3.
Curling leaves on green bean plants are symptoms of a mosaic virus disease such as bean common mosaic virus (BCMV) and bean common mosaic necrosis virus (BCMNV). These diseases most often occur with the planting of infected seeds. Seeds become infected by aphids, small sucking bugs that feed on snap beans. As aphids feed, they pierce plant tissue with their mouths, spreading viral pathogens into healthy plants. Seeds produced by infected plants are, in turn, infected as well. Different green bean varieties experience different reactions to the virus. Certain varieties are more resistant than others.
Mosaic virus diseases on green beans result not only in leaf curl but in stunted, blistered, deformed and discolored leaves. As the name suggests, leaves display a yellow and green mosaic pattern. Some green bean varieties also experience black root disease that leads to wilting, dying plant tissue and eventual plant death. Plants that develop from virus-infected seeds are more likely to become dwarfed and malformed than those infected by aphids. The greater the susceptibility of the green bean variety, the greater the crop destruction.
Resistance and Solutions
Chemical control methods are unavailable for mosaic disease. The best means of management remains prevention. Always buy seeds and plants from reliable sources. Only plant virus-free seeds and plants for best results. Plant resistant varieties, as the seeds carry genes that resist mosaic virus. Contact your county extension agent for assistance in determining which resistant seeds to plant in your particular region. Look for virus-resistant seed strains such as Mayflower, Midnight and Jaguar.