The potato psyllid sample from June 19 in Twin Falls County that tested positive for liberibacter, the zebra chip pathogen, was confirmed to be positive by gene sequencing. Samples from the following week (one from the Kimberly R&E Center and one from the same grower's field in Twin Falls County) also have tested positive for liberibacter by PCR.
A few more adult potato psyllids (collected on July 3) have been found on yellow sticky traps in two different commercial potato fields in Twin Falls County, Idaho. These samples should be tested for liberibacter this week. Numbers of psyllids continue to be rather low (1 and 3 psyllids per field), and we have yet to find potato psyllids of any life stage on potato plants themselves, suggesting that colonization of fields has not yet occurred.
Field bindweed found harboring potato psyllid eggs in a grower's field last week tested negative for PCR, which is consistent with studies by USDA-ARS, Wapato suggesting that field bindweed is not a host to Liberibacter. More field bindweed with potato psyllids was found along edges of a potato field in Gooding County, ID. Both eggs and early instar nymphs were found. Although reported to not be a host for liberibacter, this weed is a suitable host for potato psyllids. The importance of field bindweed and other alternate weed hosts of potato psyllids (e.g., nightshades) in facilitating spread of psyllids into potato fields remains to be explored, but good weed management might aid in psyllid management in potato.
We continue to encourage scouting in order to make the most sound and appropriate management steps for a given field.
Refer to the following sites for guidance on scouting and IPM programs for potato psyllids:
http://www.kimberly.uidaho.edu/potatoes/
http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/30058/pnw633.pdf