Virulent new races of rust have overcome the Ur-3 resistance gene and are now appearing in bean fields in Michigan and North Dakota, the country’s two largest bean-growing states. Ur-3-protected varieties that once withstood the disease are succumbing to it, and there's concern the new races will spread to other Northern Plains states where common beans are grown.

New cultivars of common bean developed by Agricultural Research Service and university scientists could shore up the legume crop's defenses against the fungal disease common bean rust. According to Talo Pastor-Corrales, an Agricultural Research Service plant pathologist in Beltsville, Maryland, the new cultivars possess two or more genes for resistance to the rust fungi. Most of the cultivars also harbor Ur-11, which is considered the most effective rust-resistance gene in the world.