Sam Markell, NDSU plant pathologist, reports that dry bean rust has been found in the Hope-Page, N.D., area.
"It is not known if this race of the pathogen can cause disease on bean varieties with the Ur-3 gene. The Ur-3 gene is the rust resistance gene in nearly all varieties planted in our region. The genetics of rust resistance in the infected variety are unclear. To answer the question, I took pathogen samples yesterday, but the greenhouse tests take over a month so they will not be useful for this growing season," he says.
Markell recommends scouting for rust immediately
The weather has been very conducive to rust, regardless of race, he says, and will be conducive in the future (moderate to warm temps, heavy dews).
"Rust often develops in 'hot-spots', small areas of a field (10'x10' maybe) that get significant disease. The hot spot will expand relatively quickly. Rust can cycle every 10-14 days. Initially, look for hot spots. Areas near tree rows sometimes have longer dew periods providing a more conducive environment. The middle canopy of the plant usually has more rust than the upper leaves."
Don't panic if you find rust.
It is manageable disease if found early.
"The fungicides are much better than in the mid 90's when the last epidemics hit us," he says.
If you sprayed for wild mold, those fungicides will help protect plants from rust, too.
"Proline was the best of the white mold products, but in a preventative environment (which is what white mold timing really it) other white mold products (Topsin, Endura, etc…) work to some degree. All the white mold sprays will buy time," he says.
Markell doesn't recommend preventative applications now.
"We don't know if the new race is what we are seeing so do not know if this will spread to the nearby fields. Further, fungicides can protect fields even after some rust appears, as long as it's not very severe. Folicur and generics are very good rust products. All the triazoles (Folicur, Proline, etc..) should work very well, particularly when rust is present. Headline, Quadris and the other strobilurins will work on rust, but are a better fit as preventative or in low disease severity."