At Aberdeen, UI Extension potato pathologist Jeff Miller and postdoctoral fellow Lyndon Porter are evaluating resistance to the fungicide mefenoxam in the pink rot fungus, Phytophthora erythroseptica. Tests they have conducted in the past three years indicate that more than 75 percent of this fungus' "isolates" from infected eastern Idaho tubers are already moderately resistant to mefenoxam, a chemical that's intended to control the disease.
 

"Growers should start watching for premature wilting and roots with unusual brown to black lesions," says Miller. Top-priority spots to check are both waterlogged and water-stressed areas: high, dry ridges, saturated lowlands and rows beneath end guns. "Wilting could be a sign of another disease, like early dying, but don't assume that. We'd like to check and make sure."
 

Pink rot infects tubers via fungus-infested soils. Although signs of wilt develop at the bases of stems, the worst damage occurs in the tubers themselves. When affected tubers are cut open, their "boiled textured" interiors turn pink, giving the disease its name. These discolored interiors are neither mushy nor slimy, but other diseases-including leak and bacterial soft rot-can quickly break down affected tubers in storage.
 

Pink rot struck both eastern Idaho and Magic Valley potato fields in 2003, but growers held storage losses to a minimum by detecting the disease early, keeping most infected lots out of storage, and managing their storages carefully. "So far, our weather this year has not been favorable for pink rot," says Miller.
 

Growers should send suspect potato plants to Miller (UI Aberdeen Research and Extension Center, P.O. Box 870, Aberdeen, ID 83210-0870) or bring them to their county Extension educator. For more information, contact Miller at (208) 397-4181.