MPB eyes seed testing
to control blackleg disease
PRESQUE ISLE, Maine — The Maine seed potato industry is trying to figure out how to deal with a new bacterial problem and protect a good reputation.
Last year, potato growers in the Mid-Atlantic, some of whom buy their potato seeds from Maine, experienced an outbreak of blackleg, a rotting disease caused by several species of bacteria.
That should worry Maine seed potato growers, said Steve Johnson, a crops specialist at University of Maine Cooperative Extension, in large part because it isn’t just the usual Pectobacterium atrosepticum causing the blackleg,
“This isn’t your daddy’s blackleg,” he warned at the Jan. 20, 2016 Maine Potato Conference in Caribou.
Today, blackleg is being caused by Pectobacterium as well as Dickeya, a bacteria that’s been a major problem in European potato farming for a decade and is now found in the U.S., Johnson said.
Compared to Pectobacterium, just a small amount of Dickeya can spread blackleg among potato plants. “You need so little Dickeya it’s almost undetectable,” Johnson said.
The emergence of Dickeya has raised a number of questions for Maine seed potato farmers, who rely on the Maine Potato Board’s Porter farm in Masardis for the first generation of their seed.
“There’s so many questions and nobody knows,” said Maine Potato Board executive director Don Flannery. There are the natural questions like how Dickeya got to Maine and the U.S. (That is not known). Then there are the technical questions that Flannery and others on the board are mulling, like: “Is 2 percent too high or too low?”
Two percent is the five-year blackleg tolerance level for seed potatoes that the Maine Potato Board and Department of Agriculture, Conservation and Forestry are considering as part of seed potato certification.
The Maine Potato Board is also looking to offer seed growers a screening test for Dickeya, free of charge. This will help identify “if there’s a Typhoid Mary there,” said Flannery, referring to the first American found to be a carrier of Typhoid fever.
To help with additional testing, the potato board is going to ask the Department of Agriculture, Conservation and Forestry for funding for two more part-time inspectors.
The larger U.S. potato industry industry is planning more research into understanding Dickeya and ultimately how to control it. So far, only one species of Dickeya has been found in the U.S.
In the meantime, UMaine’s Johnson believes seed farmers should be trying to avoid potential contamination in their growing and harvesting operations, which could be two potential routes of spreading.
“We’re probably in a good position to do a lot of this initial work and lead the country through how to deal with it,” Johnson said.
