OREGON STATE UNIVERSITY

Computer helps farmers curb potato famine disease

10/08/1996

ONTARIO - Most of the potatoes are out of the ground in eastern Oregon and western Idaho and it looks like better detection devices, early intervention and more favorable weather headed off substantial losses to a disease called late blight that has caused problems in recent years.

"We beat late blight on both ends of the economic scale this year," said Clint Shock, superintendent of Oregon State University's Malheur Experiment Station at Ontario.

"There were fewer losses and less money was spent on spraying to prevent late blight," added Shock. "It looks like fungicide treatment for prevention cost about $40 per acre this year compared to about $150 per acre last year."

Until recent years late blight, the disease responsible for the Irish Potato Famine in the 1840s, was not thought to be a problem in the arid climates of the American West.

However, more virulent strains seem to have developed and weather conditions aided its spread. It was first detected in Oregon around Hermiston in 1993. It was just those weather conditions that the OSU agricultural experiment station in Malheur County kept close track of this year.

"The environmental conditions most conducive for late blight growth are temperatures below 78 degrees, with humidity higher than 90 percent," said Shock.

"Though these conditions might sound unusual for this part of the country, 90 percent humidity often occurs down near the ground among the potato leaves," he said. A Malheur experiment station cooperative program helped potato growers attack the disease this year. Other members of the program team included Lynn Jensen, an OSU extension agent in Malheur County, and University of Idaho researchers Mike Thornton and Krishna Mohan. Also, the effort had support from the Oregon and Idaho Potato Commissions and the ISK Company.

"We put a lot of technology to use tracking (growing) conditions," said Shock. "We had eight remote sensing stations and dozens of cooperating field scouts and growers observing the crops. We ran automated weather data through a computer program called 'Blight cast' twice a week that gave growers a risk severity number."

For example, a severity number of 15 meant late blight could be expected to show up in 7-14 days, Shock explained. Growers could then head off the disease by applying protective fungicides.

Technology also was important in getting forecasts to the growers, he noted.

"We had an 800 number, a web page and faxes. There were about 4,000 calls to the hot line and about 2,000 visits to the web page," said Shock.

"The best way to stop late blight is to catch it early and make sure the spray covers all the leaves to kill as many spores as possible," he added. "Fungicidal treatment can provide excellent coverage early on because you can go in with tractors and spray. If it occurs late in the growing season you usually have to hire crop dusters."

Hermiston-area growers also seem to have minimized losses from late blight, according to Jeffrey McMorran, an OSU Extension agent and agronomist in Umatilla County.

"We used a slightly different computer model for our area, but we also relied heavily on field scouting reports and getting the information out to growers quickly through an 800 number and electronic mail," said McMorran.

"About 80 percent of the potatoes have been harvested. Yields are good, but not spectacular. Quality is good. There was a great fear of late blight early in the season because of the cool, damp weather conditions, but it looks like early intervention with fungicides kept it from becoming a wide-spread problem."

Shock said the OSU-Idaho research and extension team's next goal will be to fine-tune their computer program to make predictions even more accurate.

"One of the things we may do," he said, "is add additional humidity detectors at the existing AgriMet stations and place them closer to the ground - at the potato vine canopy height - so we can get more accurate humidity readings."