Spud psyllids in northern Grand Forks County

INKSTER, N.D. – Potato psyllids, an insect pest that in some parts of the country carries a serious disease bacterium, was found Aug. 26 in university research plots in northern Grand Forks County in North Dakota.

So far, none of the psyillids found in North Dakota have carried bacterium that carries dread zebra chip disease, which can make potatoes unmarketable.

Neil Gudmestad, a North Dakota State University plant pathologist, announced that he’d found the pests just prior to giving a plot tour presentation during a Northern Plains Potato Growers Association event at Inkster. The NDSU and University of Minnesota plots are in the middle of a significant potato growing area that includes, seed, chipping and processing potatoes.

Psyllids in other parts of the country can carry a bacterium for zebra chip. The disease is named and known for causing black lines in potatoes, when cooked into chips or French fries. While the potatoes are healthy to humans, they are unsightly and unsellable. The disease is in a particular problem in Texas, although not this year because psyllids

Nick David, an NDSU/U of M Extension Service potato specialist, based in Fargo, says psyllid adults are winged and probably blew in on southerly winds. He emphasized that psyllids, found earlier in August at Oakes, Dawson and Tappen, in North Dakota, so far shown no bacterium that the carries the zebra chip. He said it will be a week before that confirmation would be made from the Inkster psyllids, at Gudmestad’s laboratory in Fargo.

The early nymph stages (Stage 2 to 3) were found at Inkster. Based on that, David says it appears the pest may have been in the area up to two weeks. He says researchers were watching for the pest, this is the farthest north it has been found this far north recently. Gudmestad noted that psyllids were common as far north as Alberta prior to the hot, dry 1930s, but since have  receded back to the southern U.S.

Psyllids – even without the zebra chip factor – on their own can cause some  yield damage to potatoes, and producers were quick to want a look at zip-lock bags that Gudmestad passed out with the psyllids in them David says they can affect the quality of potatoes by resulting in misshapen tubers, although the risk is relatively low now.

The insects inject a toxin into the leaves, which disrupts the flow of nutrients from the leaves into the roots, causing the symptom known called “psyllid yellows.” Upper leaves are erect, cupped and yellow. But by the time the yellowing occurs the plant is dying and any “bulking” of potatoes for commercial size is stooped.

David says growers can uses sweep nets to find the adults, or look at plants with the characteristics of yellowing and can look on the lower parts of the plants for the nymph stage. There are insecticides  available to kill them, but at this time of the year the damage from the insects is minimal and insecticides .

NDSU research and extension personnel are hoping to develop a trapping system for early detection for next year, throughout the state, David says.