Clemson University Continues the Search for Solutions to Armillaria Root Rot

photo by JONATHAN VEIT, Clemson University


MANAGING ARMILLARIA root rot— the disease all orchardists and scientists alike recognize as the single greatest threat to stone fruit or­chard sustainability in the southeast— has gotten a recent shot in the arm for more research.


The devastating fungus commonly known as “oak root rot” causes more than $4 million per state in peach losses every year, and millions more in control costs. What can be done to halt the spread of this in­sidious, underground problem?


Researchers at Clemson University are dedicated to finding out. Though biological and chemical controls are virtually ineffective and hard on the environment, plant pathologist Guido Schnabel has de­vised a manageable solution. Trees are planted in shallow engineered berms with the top parts of roots exposed above ground. Armillaria fungus does not tolerate extreme temperatures, so it is unable to sur­vive above the soil line. This simple, low-cost solution could drastically reduce the number of trees susceptible to the disease.


Scientists have been studying Armillaria root rot for nearly 100 years. Other advances include the release of plum/peach hybrid root­stocks that have a natural tolerance to the fungus. This solution is not ideal, however, due to the fact that these hybrids generally produce a smaller tree and smaller fruit. The only really effective control tech­nique up to this point has been to avoid planting trees on land previ­ously infested with Armillaria. Now, growers can use Dr. Schnabel’s berm technique to aid in the prevention of infection.


Research on grapes showed that mycelium retreats from excavated roots. Dr. Schnabel extended this finding to investigate the effects of planting peach trees higher up initially. “It is not a silver bullet,” he cau­tions, but goes on to say that “the method does buy growers a few more years of production on replant sites.” Planting peach trees in this man­ner does make them more susceptible to drought stress during the first year, meaning that adequate irrigation must be provided to compensate.


The Advanced Plant Technology Program at Clemson University uses a variety of techniques to research plant diseases. Experts in ge­nomics, genetics, computational biology, plant pathology and physiol­ogy, molecular breeding, and more are working together to solve these expensive problems. This research is part of a larger research project by the U.S. Department of Agriculture called RosBREED. The program focuses on developing and applying modern DNA tests and related breeding methods to deliver new cultivars of rosaceous crops in 22 U.S. breeding programs.


Wells Fargo has provided $150,000 to Clemson University through the bank’s National Food and Agribusiness Division. This grant will be used to further the breeding program and find sustainable solu­tions for problems like Armillaria root rot. Stephen Kresovich, Coker Chair of Genetics and director of Clemson’s Institute of Translational Genomics, has this to say about the grant: “The funding provided by Wells Fargo will allow us to apply advanced genetic and computational techniques to build a foundation for solving a critical problem of peach orchard sustainability in the southeastern U.S. This work, if successful, will lead to a more manageable production system with a reduced need for chemical control measures.” This is good news for researchers and, more importantly, peach growers, as the quest to find a cure for this disease continues on.