It’s not rust. This is Phaseolus vulgaris: it damages the leaves with polygonal lesions restricted by leaf veins. Later the lesions merge into large spots, causing leaf yellowing and leaf drop.

Recommendation: tebuconazole or difenoconazole, ten antibiotics, copper quinoline or copper thiazolin, combined with trace element foliar fertilizer spray. Use 2 times once every 5-7 days.