Research by Jeff Miller, principal in Miller Research near Rupert, Idaho and other scientists is providing potato growers with more tools to use in controlling pink rot.
The soil-borne disease is caused mainly by the pathogen Phytophthora erythroseptica. It infects potato roots, stolons and tubers, and if not controlled can lead to significant losses in potato fields and in storage..
Finding a new treatment for pink rot proved difficult. Miller kept working on it with scientists from UI, and Washington State, Oregon State and North Dakota State universities.
Researchers experimented with a common, phosphorous-acid-based fungicide that was safe but relatively weak. They found that it, too, was ineffective at controlling pink rot — until once mistakenly applying about twice as much as intended.
“We found that we were achieving control,” Miller said. “Typically, twofold use would cause problems. But the difference was that these phosphorous acids or phosphites are very safe.”
The discovery meant growers who found the pathogen resisting Mefenoxam in their fields could instead use a phosphite. Researchers would go on to determine ideal application rates and methods — and to also find phosphites effective at reducing pink rot and Late Blight while potatoes are stored, if applied when they are going into storage.