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Recently the Roseburg City Parks arborist dropped by my office to alert me to a potential problem. The large elm tree in front of the pavilion in Stewart Park was showing signs of rapid limb dieback.
The tree had looked fine just a week to 10 days earlier but now three or four main scaffold limbs and branches were rapidly dying. The visual symptoms of the tree — leaf yellowing and limb dieback — led us to believe that this rapid dieback could be Dutch elm disease. Within a few days, the Oregon State University lab confirmed that thought.
Dutch elm disease came to the U.S. in 1930 from logs imported from Holland. The disease originated in the Orient. European and American species of elm are all susceptible at varying degrees.
After arriving in North America, the disease spread to nearly all areas of the country. The fungal pathogen is spread by elm beetles from tree to tree. When beetles feed on a tree, they introduce the fungus into the water transport system (xylem), and the fungus grows downward toward the roots. Eventually nearly all water and nutrient flow is blocked. Gums and tyloses build up in the xylem and eventual death occurs to the tree. You will usually see brown streaking in the wood of a diseased tree where dieback has occurred.
Now that the virulent elm disease is in our community, it is critically important that we begin to be proactive to adopt the best practices to prevent the spread of Dutch elm. This is especially important because of the historical and aesthetic value the courthouse elm has in our community. If we would like to improve the odds of our courthouse elm surviving for many more years, all of us need to keep our eyes open for any dieback going on with elm trees.
If you see an elm tree with some dieback, please contact the extension office. You should also follow the suggestions below if you have an elm on your property.
Sanitation: If you have a tree that has some dieback, have it tested for Dutch elm disease. If the tree tests positive, get it cut down quickly and either burn or bury the remains. If you spot one limb dying back and you catch it early, you can prune about 10 feet below the wilting limb. This may remove the disease before it gets into the trunk and roots. Have a certified arborist work with you to eliminate the spread of this disease.
Preventive fungicide injections: Some fungicides will prevent the infection, but the process is expensive and will last only a couple years. Drilling holes in the root flair of a tree to make the injection can open the tree to infection. This is the only preventative method.
Since the fungal disease and vectors are in our area, the courthouse elm has had an injection treatment to remain a healthy pillar in our community for years to come.
Steve Renquist is the Horticulture Extension Agent for OSU Extension Service of Douglas County. He can be reached by e-mail at steve.renquist@oregonstate.edu or by phone at 541-672-4461.
The tree had looked fine just a week to 10 days earlier but now three or four main scaffold limbs and branches were rapidly dying. The visual symptoms of the tree — leaf yellowing and limb dieback — led us to believe that this rapid dieback could be Dutch elm disease. Within a few days, the Oregon State University lab confirmed that thought.
Dutch elm disease came to the U.S. in 1930 from logs imported from Holland. The disease originated in the Orient. European and American species of elm are all susceptible at varying degrees.
After arriving in North America, the disease spread to nearly all areas of the country. The fungal pathogen is spread by elm beetles from tree to tree. When beetles feed on a tree, they introduce the fungus into the water transport system (xylem), and the fungus grows downward toward the roots. Eventually nearly all water and nutrient flow is blocked. Gums and tyloses build up in the xylem and eventual death occurs to the tree. You will usually see brown streaking in the wood of a diseased tree where dieback has occurred.
Now that the virulent elm disease is in our community, it is critically important that we begin to be proactive to adopt the best practices to prevent the spread of Dutch elm. This is especially important because of the historical and aesthetic value the courthouse elm has in our community. If we would like to improve the odds of our courthouse elm surviving for many more years, all of us need to keep our eyes open for any dieback going on with elm trees.
If you see an elm tree with some dieback, please contact the extension office. You should also follow the suggestions below if you have an elm on your property.
Sanitation: If you have a tree that has some dieback, have it tested for Dutch elm disease. If the tree tests positive, get it cut down quickly and either burn or bury the remains. If you spot one limb dying back and you catch it early, you can prune about 10 feet below the wilting limb. This may remove the disease before it gets into the trunk and roots. Have a certified arborist work with you to eliminate the spread of this disease.
Preventive fungicide injections: Some fungicides will prevent the infection, but the process is expensive and will last only a couple years. Drilling holes in the root flair of a tree to make the injection can open the tree to infection. This is the only preventative method.
Since the fungal disease and vectors are in our area, the courthouse elm has had an injection treatment to remain a healthy pillar in our community for years to come.
Steve Renquist is the Horticulture Extension Agent for OSU Extension Service of Douglas County. He can be reached by e-mail at steve.renquist@oregonstate.edu or by phone at 541-672-4461.
