April 15, 2009

NNY Research Project Developing Strategies to Manage Brown Root Rot

Northern New York has the dubious distinction of being the first region to identify the presence of brown root rot in the state, but it can also claim a proactive approach to dealing with the cold weather-active, soil-borne disease caused by the fungus Phoma sclerotioides that affects alfalfa crops.

A 2009 Northern New York Agricultural Development Program project has Cornell University plant pathologist Gary C. Bergstrom, graduate student Michael Wunsch, and plant breeders Julie Hansen and Donald R. Viands assessing the range of brown root rot (BRR) in NNY and beginning to develop BRR management strategies.

The research team members say they have the opportunity to address one of the factors contributing to reduced productivity and longevity of alfalfa crops by identifying alfalfa varieties that better withstand the fungus in BRR-infested soils in NNY.

“Brown root rot is most severe in regions with harsh winters such as Northern New York. Because there are at least four genetically distinct biotypes of the brown root rot fungus present in New York and the relative resistance of alfalfa varieties to brown root rot appears to differ by biotype, the testing of alfalfa varieties for resistance in the naturally-infected soils of Northern New York has great value in the identification of varieties that will have the potential to grow well in the region,” says Bergstrom.

To help the efforts to develop BRR management strategies, farmers can scout their fields now for the crop damage caused by the fungus.

“April through early May is the best time to assess over-wintered alfalfa for signs of brown root rot on roots and crowns. If alfalfa that looked great last October is slow to emerge this spring or appears to have ‘winterkilled,’ brown root rot may be a contributing cause,” Bergstrom says.

Absolute confirmation of brown root rot (BRR) requires a laboratory test that is now available from the Cornell University Plant Diagnostic Clinic. Farmers should call 607-255-7850 prior to submitting samples. The test costs $40 per composite field sample.

Michael H. Davis, an agronomist with the Cornell University Agricultural Experiment Station at Willsboro, notes, “This pathogen could significantly impact dairy farmers in Northern New York. The brown root rot experiments being conducted on the E.V. Baker Research Farm in Willsboro and the agronomy plots at the W.H. Miner Agricultural Institute in Chazy, are an important step toward the development of an effective management strategy.”

Researchers have found that forage grasses such as bromegrass, tall fescue, orchardgrass, reed canary grass, perennial rye, and timothy are all moderately susceptible to P. sclerotioides. The forage grasses do not suffer as much damage as alfalfa crops, but act as a host reservoir for the pathogen.

“We have not yet diagnosed an alfalfa field as lost to brown root rot in Lewis County, but the Cornell survey has alerted us that the pathogen is present in the county. Although it does not appear brown root rot will have a significant impact on forage grasses, knowing that the grasses can harbor the pathogen and continuing research to develop management strategies and BRR-resistant varieties of alfalfa will be important in reducing the chances for problems for our alfalfa growers,” says Field Crops Educator Joseph R. Lawrence with Cornell Cooperative Extension of Lewis County.

Dairy farmer Dan Chambers of Heuvelton in St. Lawrence County grows 450 acres of alfalfa and forages. He says, “Farmers have to be vigilant about scouting crops for problems. The region-specific research made possible by the Northern New York Agricultural Development Program, the New York Farm Viability Institute, state funding and Cornell provide us with valuable information and resources to prevent or reduce crop damage and economic losses.”

Bergstrom and Wunsch say, “There is no action that alfalfa producers can take currently to control BRR, but with the support from the Northern New York Agricultural Development Program we expect that ongoing research will change that.”

Brown root rot was first confirmed in New York State in Clinton County in 2003 in Cornell test plots at the W.H. Miner Agricultural Research Institute in Chazy. Brown root rot is now known to occur throughout New York State, Vermont, New Hampshire and Maine.

Photos showing the damage the disease causes on alfalfa on the Northern New York Agricultural Development Program website with the results of other regional on-farm research at www.nnyagdev.org. # # #

• Gary C. Bergstrom, Cornell University, 607-255-7849
• Michael H. Davis, Cornell University Agricultural Experiment Station at Willsboro Farm Manager, 518- 963-7492
And Cornell Cooperative Extension:
• Clinton/Essex counties: Anita Deming, 518-962-4810
• Franklin/St. Lawrence counties: Stephen Canner, 315-379-9192
• Jefferson County: Mike Hunter, 315-788-8450
• Lewis County: Joe Lawrence, 315-376-5270