Heat may have bright side -- fewer potato psyllids
By JOHN O'CONNELL
Though Idaho growers fear the arrival of a record-setting heat wave could stress crops, it may have come with a silver lining for potato farmers, according to Andy Jensen, regional research director for the Washington, Oregon and Idaho potato commissions.
Laboratory research has found neither potato psyllids nor the Liberibacter bacterium they harbor, which causes the spud disease zebra chip, fare well in intense heat.
"There have been lots of lab experiments to show potato psyllids don't reproduce well, if at all, in hot weather, and Liberibacter doesn't survive well in psyllids in hot weather," Jensen said. "They really start to do less well in the low 90s. It's possible the heat will slow down the psyllids."
Jensen offered the caveat that psyllids are also mobile and adept at finding more moderate temperatures.
During June, 16 heat records were set at the five Idaho locations in which records have been kept for at least 30 years, according to the National Weather Service. Pocatello set five record highs, Idaho Falls broke four records, Challis and Stanley each set three records and Burley set a record.
On June 30 alone, Pocatello recorded a 98-degree high temperature and Idaho Falls reached 97 degrees, both breaking records set in 2008, and Stanley's 88-degree high broke a record set in 1976. National Weather Service predicted temperatures would drop closer to normal beginning July 4 and stretching through the weekend before returning to record levels again on Monday and Tuesday.
Zebra chip first arrived in the Pacific Northwest in 2011 and creates bands within tuber flesh that darken when fried.
In the Columbia Basin, Jensen, who recently completed a series of grower workshops in identifying psyllids, said the tiny, cicada-like insects were detected in potato fields in late May, much earlier than expected.
"There were not big numbers, but they were moving around, and they were getting caught on traps," Jensen said.
Psyllids have been found in more locations through June in Idaho, though Jensen attributes that fact to a significantly expanded monitoring program this season.
"The number of counties psyllids have been found in has gone up," Jensen said.
In early June, scouting efforts detected an adult psyllid and several eggs on bittersweet nightshade, a host crop, in Twin Falls. A few weeks later, a single psyllid was found in Canyon County. In late June, four more potato psyllids were found in Canyon County fields, two psyllids were found in Tiwin Falls County, one was found in an Elmore County potato field and one was found in Ada County, according to an update issued by University of Idaho.
Jensen also found psyllids overwintering in the Boise area both this season and last season.