Hello Melanie,

Raising vegetables is always a challenge because many are susceptible to disease. I cannot tell for certain what is happening with your beans, but given the photos, I can see two possibilities causing the symptoms in your beans. I am also providing links to more information on the diseases causing these symptoms and possible treatments. Unfortunately, as with most vegetables, by the time symptoms of this severity become evident, treatment may be difficult. I suggest that you monitor your green beans against the information provided to identify which disease is causing the symptom and then treat accordingly and prepare, as the links suggest, for next year’s crop.

The first possible disease is rust, a fungal infection common to vegetables. It causes curling and darkening of leaves. I think this is very likely a cause of the symptoms in your beans because fungal infections tend to increase after a wet spring and I believe we had a wet spring this year. See the link below on more information. Treating for rust is involves cultural practices as described in the link below.

https://extension.colostate.edu/topic-areas/agriculture/rust-of-dry-beans-2-936/

The other possible disease is a mosaic virus, which is transmitted by aphids. You can check for the presence of aphids on your bean plants. Mosaic virus infections also create curling and darkening of leaves, similar to rust. I found a link from another extension site that does a pretty good job of describing potential viral infections. I suggest reviewing the attachment and monitor your beans to see if it is a viral infection. The most effective treatment is prevention by ensuring your bean seeds are free of the virus or to ensure you have a resistant variety of beans.

https://www.vegetables.cornell.edu/pest-management/disease-factsheets/virus-diseases-of-snap-and-dry-beans/