A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

July 30, 2004
From: Idaho State Journal, Pocatello, 28 Jul 2004 [edited] <http://www.journalnet.com/articles/2004/07/28/news/local/news08.txt>

Second case of late blight found in Bingham County, Idaho

Potato experts confirmed a 2nd case of late blight, a potato disease, in a Bingham County field Tuesday. Potato disease specialist Jeff Miller said the 2 cases are probably unrelated -- the fields are several miles apart. Both cases are cause for concern, he said.

Miller said that the potato disease was discovered in 1 field Monday in south Bingham County, and the 2nd was found Tuesday. Miller said both farmers plan to destroy affected portions of their fields to avoid spread.

Late blight is the potato fungus involved in the Irish potato famine in the 1850s. It first occurred in Idaho in 1995 and in 1997 it devastated potato crops. The disease is common in more moist climates, but hasn't been prevalent in Idaho for a few years, Miller said.

Chemicals are effective, he said, but because the fungus is rarer in southeast Idaho, many fields are not sprayed often. "There are a lot of fields in Idaho that are unprotected."

While the discovery of late blight in southeast Idaho fields is cause for concern, it isn't a big surprise. Forecast models created at the University of Idaho predicted late blight would appear in Idaho potatoes during 2004, Miller said. Considering the regular thunderstorms and rain, it's not unexpected said University of Idaho student Extension Educator William Bohl. If the wet weather continues, the disease could become hard to control.

Bingham County has been hit by regular thunderstorms and rain, Bohl said, creating good conditions for the fungus. Miller is encouraging farmers to walk their fields as much as possible, and to spray more often. Fungicides are like sunscreen, he said. It protects only where it has been applied, and it must be reapplied regularly.

[Byline: Emily Jones]

[Potato late blight, caused by _Phytophthora infestans_ can, if unchecked, result in catastrophic losses. The current University of Idaho recommendation, if a protectant fungicide has not been applied in the past 7-10 days is to put on an immediate application of fungicide. For those who have applied a protectant fungicide, the  recommendation is stay on a 7-10 day fungicide spray schedule.

General strategies for disease management include forecasting and reporting programs to predict late blight incidence, cultural control (strict adherence to sanitary regimens to bury and compost culls, removal of volunteer plants, avoidance of over-fertilization with nitrogen, avoidance of solanaceous crops such as tomato, pepper and
eggplant in any crop rotation, and use of certified seed). Unfortunately, there are no resistant cultivars, although some cultivars such as Kennebec, Sebago and others express some resistance and are being used in breeding programs. Compost teas made from horse or cow manures in combination with beneficial bacteria are being
investigated as possible alternative fungicides.

An interesting article: http://attra.ncat.org/attra-pub/lateblight.html - Mod.DH]