Brown root rot has become widespread in New York, Vermont and New Hampshire and has been detected in Pennsylvania and Maine, according to Cornell University plant pathologists.

This potentially serious forage-crop disease was found in eight of 10 fields sampled in New York state, six of seven fields sampled in Vermont and five of six fields sampled in New Hampshire. "It's pervasive. These were arbitrarily chosen fields, and it is present in a majority of alfalfa fields tested in the Northeast," says Gary Bergstrom, Cornell University plant pathologist. "At this point, we have not identified effective controls for it," he adds, explaining that scientists are exploring disease-resistant varieties that are adapted to the Northeast.

The disease's lesions begin as reddish-brown to dark brown areas of external discoloration. As the lesions progress into the internal plant tissues, they can take on a corky texture, with a dark border separating healthy and diseased tissue. Lesions that do not immediately kill the plant can vary in appearance, making it difficult to identify the disease without laboratory analysis. "It was found in a high percentage of plants in many fields, and most lesions had advanced to the internal tissues of roots and crowns," says Bergstrom. "This suggests that it may be a serious factor in the health and persistence of alfalfa in the region."

In North America, brown root rot has been a problem in Alaska and in Alberta, Saskatchewan, Manitoba and the Yukon Territory of Canada. In eastern North America, it had been reported only in Nova Scotia. The disease was first observed in the contiguous U.S. in 1996 in Wyoming and then subsequently in Idaho, Montana, Minnesota and Wisconsin.

Contact Bergstrom at 607-255-7849.