Northern New York growers whose alfalfa crops were slow to break dormancy this spring may need to check fields for brown root rot (BRR), say Cornell University plant pathologists.

The Northern New York Agricultural Development Program (NNYADP) has provided funding to continue research into the crop disease that can cause losses in excess of 60% in alfalfa and other perennial forage crops. Earlier NNYADP-funded research surveyed alfalfa fields in northern New York and identified a complex of seven biotypes of the fungus Phoma sclerotioides that causes BRR.

BRR was first discovered in New York State in Clinton County in 2003. One of the seven biotypes has been named P. sclerotioides var. champlainii, indicative of the county’s proximity to Lake Champlain and the fact that the disease has also been found on the Vermont side of the lake.

BRR causes lesions on the taproots and crowns of alfalfa and other perennial legumes. Symptoms develop in late winter and early spring. Severely affected plants often fail to emerge from winter dormancy or exhibit delayed spring regrowth.

“State funding of the NNYADP has helped New York agriculture inestimably by providing the means to continue research into BRR,” says Cornell plant pathologist Gary Bergstrom.

“Our research in northern New York farm fields has shown as many as five of the seven biotypes, sometimes five in a single field.”

With Michael Wunsch, Bergstrom co-authored a phytopathology professional journal article on the biotypes. Wunsch, who was the primary researcher on the BRR project, now is a plant pathologist at North Dakota State University’s Carrington Research Extension Center.

“The identification of subtypes of the brown root rot pathogen is expected to facilitate growers’ improved management of the disease,” he says.

The NNYADP has designated 2011 project funding from the Cornell University Agricultural Experiment Station for the selective breeding and field trials of BRR-resistant alfalfa varieties.

The Cornell research team includes plant breeder Donald Viands and Julie Hansen, plant breeding and genetics senior research associate.

BRR is known to impact alfalfa and other perennial forage crops in central, northern and eastern Canada, in areas from the Rocky Mountain states south to New Mexico, in the Upper Midwest, and in New England and Pennsylvania.

More information on BRR research is posted under Grass-Based Agriculture on the NNYADP Web site at www.nnyagdev.org.