Late blight, heat stress and psyllids. Those seem to be three issues of concern for growers in the Columbia Basin at this time.
Dennis Johnson's late blight hotline reports that late blight has been found in five fields south of Basin City in Washington state.
For more information on late blight and how to treat the disease, Syngenta sponsors a late-blight phone number in the following states: Idaho, 800-791-7195; Michigan, 888-379-9012; Oregon, 800-705-3377; North Dakota, 888-482-7286; and Washington, 800-984-7400.
A couple of Idaho growers I spoke with at the U.S. Potato Board summer meeting in Klamath Falls, Ore., said they were seeing early signs of heat stress in their fields prior to leaving for the USPB meeting.
Of greater concern throughout the Pacific Northwest is the threat of potato psyllids carrying liberibacter, the bacterium that causes zebra chip disease.
At Oregon State University's Hermiston Research and Extension Center, entomologist Silvia Rondon and director Phil Hamm report that two out of 13 psyllids tested positive for liberibacter in the first week of August. The two positive samples were collected from the Cold Springs area and from a field at the Hermiston center.
"Finding some positive plants is not unreasonable, and certainly something to be concerned with, but not to lose any sleep over," Hamm said. "As long as you are following recommendations that Silvia has given related to insecticides to use, at what rate and at what time, some of the disease in your field might be expected, but certainly a very low percentage."
Rondon encourages growers to actively scout for psyllids in their fields. She said that growers are bringing in samples on an almost daily basis. After confirming the insects are psyllids, they send the samples to Hamm's lab, where they do Polymerase Chain Reaction (PCR) testing to determine if they are liberibacter positive.
Rondon said that she and her staff are busy testing the efficacy of insecticides on psyllids found in the Pacific Northwest. Until now, almost all Integrated Pest Management data on psyllids has come from Texas.
"That's where the problem started — when this insect started moving from Central America up to Texas and then up north, reaching us here in 2011," Rondon said.
"We want to know if the chemicals that really do work well in Texas do work here in our conditions, which are different," Rondon said.
"The big picture is that there are some psyllids out there that have liberibacter in some areas — but apparently not in all areas, at least given the samples we've collected thus far," Hamm said.
For up-to-date information on psyllids and zebra chip findings in Oregon, visit http://oregonstate.edu/dept/hermiston/trap-reports.
On July 24, entomologist Erik Wenninger, of the University of Idaho Kimberly Research and Extension Center, said potato psyllids continue to be found across several state sites being monitored by the university. The number of psyllids at the Kimberly Research & Extension Center and at a grower's field in Twin Falls County were up considerably, with 16 potato psyllids trapped on yellow sticky cards at the Kimberly center, and 54 potato psyllids trapped in the Twin Falls County field.
An additional eight psyllids were trapped on sticky cards in Jerome County, and one was trapped in a field in Twin Falls County.
At that time, potato plants infected with zebra chip had been confirmed by PCR testing at three locations in Twin Falls County and one location in Minidoka County. Plants with zebra chip symptoms have been collected or reported from other locations, but have not been confirmed with PCR test results.
The most recent report of Aug. 9 stated that during the past week mature potato psyllids were found on sticky cards in the Magic Valley and no immature potato psyllids have yet to be found on leaf samples taken from potato fields.
For the latest information on psyllid and zebra chip findings in Idaho visit, http://www.kimberly.uidaho.edu/potatoes/