FORMAN, N.D. — A fatal plant disease has been confirmed in North Dakota trees for the first time, posing a major threat to windbreaks and community forests statewide.
The North Dakota Forest Service reported that pine wilt disease was detected in Ransom and Sargent counties after staff investigated die-offs in Scotch pine trees at the Sheyenne River State Forest and near Forman. The finding was confirmed Aug. 11 by the South Dakota State University plant pathology lab.
The disease is caused by microscopic nematodes spread from tree to tree by native sawyer beetles. The pests target non-native conifers—including Scotch, Austrian, and Mugo pines—by collapsing the tree’s water-conducting pores. Infected Scotch pines usually die within a single season, while Austrian pines typically succumb within two.
Forest Health Manager Martin Shervey warned that no effective chemical treatment exists to cure infected trees.
“Removal and destruction of the wood is the best treatment to slow the spread of the disease,” Shervey said.
With rising summer temperatures, officials expect pine wilt to move northward across the state, mirroring a trend previously observed in South Dakota. Because non-native pines are widely planted in farmstead windbreaks and community landscapes, foresters are urging landowners to diversify tree species and consider native options, such as Ponderosa pine, for future plantings.
Landowners who suspect their trees are infected should submit a report through the Sick Tree Assistance form on the North Dakota Forest Service website or contact a local extension agent. Lab confirmation requires active nematode samples, which can only be collected through early September.
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