Idaho Potato Psyllids test positive for zebra chip disease

The University of Idaho extension today announced that the potato psyllids found last month in Idaho tentatively tested positive for Liberibacter, Zebra Chip disease.

Zebra Chip disease is a threat to potato quality for growers and processors, zebra chip can reduce the value of both fresh and process potatoes. It particularly affects processed products such as French fries and potato chips by creating darker chips and fries. The dark coloration results from changes in stored sugars that caramelize when the potatoes are processed. Potato products showing signs of zebra chip are removed before packaging due to their appearance.

University of Idaho Extension statement:
 

Adult psyllids collected from a sticky card on a commercial field in Twin Falls County on June 19 have tentatively tested positive for Liberibacter, the bacterium that causes zebra chip. PCR tests conducted last week by Alex Karasev’s lab are being followed up this week by sequencing the bands to confirm that the sequences belong to Liberibacter. In the mean time, additional psyllids collected last week from this site and from the U-Idaho Kimberly R&E Center will be tested this week for Liberibacter.

We still have not found psyllids of any life stage on potato plants themselves. However, field bindweed was found along the edge of the field near the sticky card with “hot” psyllids, and today we found potato psyllid eggs (but no other life stages) on several field bindweed plants. The importance of this finding in relation to psyllid infestations in potato remains to be explored, but, considering potato psyllids have a broad host range that includes at least 20 plant families, weed management might aid in psyllid management in potato fields. The infested field bindweed also will be tested for Liberibacter.

This is the first (preliminary) finding of Liberibacter-infected psyllids in the Pacific Northwest this season;however, we still strongly recommend that fields be scouted in order to make the most sound and appropriate management steps for a given field.

Last year zebra chip disease showed up for the first time in the Pacific North West, including Idaho. At the time several confirmed reports were made in Twin Falls County. Although the pest was found in several fields, the number of plants infected initially appeared low.

University of Idaho Extension potato specialist and storage researcher Nora Olsen last year:

"The question is whether this is an artifact of the unusual weather we had earlier this year or whether this is going to be a long-term problem."

We might already have a preliminary answer to that question.