Rusty orange pustules on the underside of my French bean leaves

Rusty orange to brown raised pustules on the underside of bean leaves with pale yellow spots above, leading to drying and leaf drop in humid weather, are bean rust, a fungal disease. It spreads by spores in moist conditions and can defoliate the crop if unchecked. Remove and destroy heavily infected leaves and old crop debris which carry the spores, improve spacing and airflow, and avoid overhead irrigation and working in the crop when wet. Spray a protectant fungicide such as mancozeb or wettable sulphur at first signs, and use a systemic like a triazole if it is spreading, rotating groups to avoid resistance. Choose resistant varieties for the next crop where available and rotate away from beans for a season in badly hit fields. Since beans are eaten fresh, follow the label dose and pre-harvest interval, and confirm the diagnosis with your KVK before spraying.