Sudden Oak Death Canker Treatment
Image courtesy of Joseph O'Brien, USDA Forest Service, Bugwood.org
A New Technique to Arrest Sudden Oak Death Canker Development
Sudden Oak Death (SOD) is caused by Phytophthora ramorum. Several species of oak and tanoak are susceptible.
Once infection occurs, disease can spread rapidly to the inner bark and sapwood resulting in stem girdling and death of the host tree. SOD treatment has several combined approaches that depend on tree susceptibility and condition. To date, thousands of oaks have been successfully treated in using phosphite fungicides.
Phosphites are systemic fungicides. When absorbed by stem tissues, the phosphates stimulate production of defensive compounds within plant cells. At high concentrations, phosphite can also act directly on Phytophthora to inhibit its growth. So far, phosphites have proven to be the most effective preventive treatment for healthy oaks.
Once infection occurs, phosphite treatments may slow progression of SOD but, unfortunately, will seldom stop the disease progression completely. The majority of oaks affected will eventually die. This is where an innovative new technique being used by Bartlett Tree Experts comes in.
In this technique, arborists rapidly excises bark at the margins of SOD cankers using a power planer. Diseased tissue at the margin of the canker is exposed, minimizing injury to healthy inner bark and sapwood outside of the cankered area. Similar techniques have long been successful in managing canker diseases, including Phytophthora canker on fruit trees.
A planer exposes the leading edge of a Phytophthora canker to stop further progress of disease into healthy bark tissues. Any dead tissue in the interior portion of the canker is also left undisturbed because Phytophthora does not survive on dead tissue.
After diseased bark tissue is excised, the stem is sprayed and injected with fungicide, which further helps to arrest the growth of Phytophthora and aid in tree recovery. Observations indicate that SOD canker development can be arrested as long as treatments are applied in the early disease stages. Once cankers encompass more than a third of the trunk circumference, tree health and stability are severely compromised. Trees with symptoms on more than one third of the stem circumference are poor candidates for treatment.
This treatment regime from Bartlett Tree Experts is an exciting new technique to preserve oaks that have Sudden Oak Death disease.
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