At least two fields in western Idaho were found to exhibit a high incidence of severe zebra chip symptoms in tubers last week. The incidence is estimated to be upwards of 60 percent. Samples are on their way to the University of Idaho campus for confirmation of zebra chip by molecular testing. Unfortunately, these fields were not part of UI’s psyllid monitoring network; however, this development supports the need to maintain an integrated pest management program targeting psyllids through the end of the season.
Only one potato psyllid collected last week in UI’s monitoring program tested positive for Lso (liberibacter), the bacterium that causes zebra chip. The Lso-positive psyllid was found in a single Payette County field.
Potato psyllids were collected this week on sticky traps in potato fields in the following counties: Malheur (Ore.) (1 field), Payette (three fields), Owyhee (five fields), Canyon (13 fields), Ada (two fields), Elmore (two fields), Gooding (two fields), Twin Falls (five fields), Jerome (three fields), Minidoka (two fields), and Cassia (four fields).
Additionally, potato psyllid nymphs (22 total) were captured on leaf samples from Ada County (two fields) and Canyon County (two fields), with 38 potato psyllid adults being captured from vacuum samples taken from four “intense”-labeled fields in the following Canyon, Ada and Gooding Counties.
UI researchers collected 690 psyllids last week from sticky cards (556 from “light” sites and 134 from “intense” sites). Of the total 728 psyllids captured last week, 643 came from the Treasure Valley. Psyllids were found in 43 of the 83 fields (52 percent) sampled last week. Several cards did not come in last week, but will be processed when they hopefully arrive this week.
Because of the recent prevalence of Lso and the relatively high numbers of potato psyllids that have been collected each week, growers are urged to maintain their IPM programs targeting psyllids and to be on the lookout for plants exhibiting zebra chip symptoms over the coming weeks. Foliar symptoms should be manifested about three weeks following inoculation, but will need to be confirmed by examining and testing tubers. Growers are encouraged to take suspicious plant samples to the Kimberly R&E Center or the closest UI Extension Center.
Detailed results from the “light” sites can be found here.
Detailed results from the “intense” sites can be found here.