What is causing the leaves of our pole beans to have brown spots and holes?
That looks like it may be a fungal leaf spot. I recommend that you apply a preventative fungicide, such as chlorothalonil (Daconil), according to label instructions on application interval and such, remove any affected foliage, seal it in a bag, and dispose of it. It is best to water in the morning at the base of the plant, keeping the foliage dry, to prevent some disease problems. Mulching around plants helps to conserve moisture, keep weeds down, and prevent some disease problems by preventing splashing up onto the leaves.