PSYLLIDS SHOW FAR LESS ZC THIS YEAR
About the same number of potato psyllids have been caught on sticky traps in Idaho fields this season as by this time last summer, but far fewer of the tiny, winged insects have tested positive for the Liberibacter bacterium, which causes the crop disease zebra chip.
Zebra chip ruins tuber appearance with bands in flesh that darken when fried.
University of Idaho Extension entomologist Erik Wenninger said only six of more than 100 psyllids collected throughout Idaho have tested positive this season, compared with about half of the psyllid population tested last season. He now suspects last season's infection rate was an anomaly.
"I think the incidence (of psyllid infection) we're finding now is maybe more typical of what we might expect to find," Wenninger said. "Work in the central U.S. suggests 1 to 4 percent is about typical, and we're somewhere in that range this year."
Idaho confirmed its first three positive psyllids, captured in separate Canyon County fields and at the Kimberly Research and Extension Center, during the first week of July. Three more psyllids tested positive from cards collected July 22 from separate fields in Jerome County and one from Canyon County.
Psyllid testing programs based at Oregon State University and Washington State University have each detected a single infected psyllid.