A photo would help. Bush beans or pole beans?

Possible causes could include root damage like from moles or other root pests, primary stem injury, or watering issues to name just a few. Most diseases issues would have shown on the leaves first but fusarium wilt is a possibility as is what is called Sudden Death Syndrome, another soil borne fungus disease. However I'd expect symptoms of them to show up at a younger plant age but you can Google both diseases and compare symptoms.

Nematode issues would also show on the roots.

Dave

Thanks never saw that before but I am in soybean country so if it can effect bush green beans could be what it is. Never had that up north away from farming. Spose nothing can be done to stop it?