A survey to determine distribution and intensity of cankers and associated damage in North Dakota windbreak plantings of Russian-olive and Siberian elm was conducted in 1972. Four hundred and thirty-five (76 percent) of 574 Russian-olive examined had cankers, and 552 (72 percent) of 769 Siberian elm examined had cankers. Cankers on trees in all windbreaks except one contained the secondary fungi Cytospora sp., Dothichiza sp., and Camarosporium sp. Tubercularia ulmea, the reported pathogen, was recovered from only one windbreak. Most cankers were on small twigs and branches. The cause of windbreak decline appears to be herbicide injury, with root pruning caused by close cultivation, and soil compaction caused by livestock exerting minor effects in localized areas. Recommendations are made to reduce windbreak decline.