Farmers have a new weapon in their arsenal in detecting and combating the soil-borne plant pathogen Phoma sclerotioides, commonly known as brown root rot/BRR, thanks to Cornell researchers.
First detected in the eastern United States in Clinton County in 2004, BRR is a cold-weather disease affecting the roots and crowns of alfalfa and other perennial legumes during the dormant period when plants are not actively growing.
It is most severe in regions with harsh winters such as in northern New York and northern New England, and other stresses to alfalfa plants interact with BRR to cause plant death. Winterkill and weak regrowth of alfalfa were prevalent this spring, and brown root rot may have contributed to the damage in different areas, according to plant pathologist Gary Bergstrom.
“The widespread finding of BRR in association with winterkill represents an opportunity to reverse one of the main factors that reduces the productivity and longevity of alfalfa in our region,” Bergstrom said.
He worked with graduate student Michael Wunsch, now the plant pathologist at the Carrington Research Extension Center of North Dakota State University, to develop an improved molecular test for BRR. The new tool is a polymerase chain reaction (PCR) test that is 10 times more sensitive in detecting DNA of the pathogen than those previously available. It’s also much quicker than the two to three months it previously took to culture the fungus, said Karen Snover-Clift, director of the Cornell University Plant Disease Diagnostic Clinic, which will be administering the test.
While there is currently no “cure” for BRR, farmers may consider planting a mixed crop of alfalfa and other perennial grasses to help cope with the pathogen.
“While the roots of overwintering grasses also harbor brown root rot, this disease is unlikely to cause reductions in the survival or yield or perennial grasses,” Wunsch said.
“There is no action that an alfalfa producer can take currently to control BRR, but we hope that ongoing research at Cornell University and elsewhere will change that,” Bergstrom added. “With support from the Northern New York Agricultural Development Program we are assessing alfalfa varieties adapted to this region in BRR-infested soils in order to identify varieties that may perform better than others in the presence of the BRR fungus.”
