Nov. 15, 2007 Cornell University plant pathologists have detected brown root rot - a potentially serious forage crop disease - in the Northeast United States. The scientists report that it is widespread in New York, Vermont and New Hampshire. Brown root rot (Phoma sclerotioides) has also been recently found in Pennsylvania and Maine.
This disease affects dairy farmers, as it attacks forage crops alfalfa and clover. "It's pervasive. These were arbitrarily chosen fields and it is present in a majority of alfalfa fields tested in the Northeast. At this point, we have not identified effective controls for it," said Gary Bergstrom, Cornell professor of plant pathology. He explains that scientists are exploring disease-resistant varieties that are adapted to the Northeast.
Brown root rot was detected 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.
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 corky texture, with a dark border separating the 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.
Says Bergstrom: "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. This suggests that it may be a serious factor in the health and persistence of alfalfa in the region."
Michael Wunsch, Cornell graduate student in plant pathology and the lead author of this research, says that spatial patterns within fields suggest the pathogen was not recently introduced in the Northeast. Within 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 United States in 1996 in Wyoming and then subsequently in Idaho, Montana, Minnesota and Wisconsin.
Bergstrom suggests that if farmers in New York have questions about brown root rot in their fields, the farmers should contact the Cornell Cooperative Extension field crops educator for their county. Outside of New York, farmers should contact their local cooperative extension office.
The other authors on the study, "Distribution, Impact, and Soil Environment of Phoma sclerotioides in Northeastern U.S. Alfalfa Fields," are: Robert Schindelbeck, research support specialist, and Harold van Es, professor, both of crop and soil sciences.
This research is reported in the October 2007 issue of the journal Plant Disease.
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