Bleeding Cankers on Beech trees, particularly mature trees, in Westchester County is a big problem
Bleeding Cankers on European Beech -- An Update
Last year, Dr. George Hudler -- plant pathologist at Cornell University -- tested a variety of proprietary compounds for management of bleeding cankers on European beech caused by Phytophthora spp. Work began in the spring of 2004 with applications of Agri-Fos, one of several formulations of phosphorous acid that have recently shown up on the market. He followed a protocol recommended by company representatives and scientists at the University of California calling for a bark drench (to a height of six to eight feet) with a mixture of 31.2 fl. oz. Agri-Fos plus 31.2 fl. oz. water plus 1.6 fl. oz. of Pentra-Bark". The latter is an adjuvant that is supposed to promote movement of the Agri-Fos through the outer bark and into the living phloem and cambium. Most of the trees we treated were in the 30-40 inch stem diameter class, and they used about 1/2 gallon of mixture per tree.
When he examined the trees five months later (October 2004), the cankers were still oozing and there was no evidence that the treatments had been effective. However, a second exam about four weeks ago (August 2005) was more encouraging. Cankers less than about one square foot in area were no longer oozing fluid and, in comparison to pictures taken just before treatment, appeared to be the same size that they were at the beginning of the observation period.
Unfortunately, the experimental design was far from optimal inasmuch as there were no untreated trees on the same properties as the treated trees and on all but one of 12 properties he worked on there were only one or two diseased trees. Thus, he cannot be sure that the apparent improvement is a result of the treatment or some other factor such as the persistent drought in 2005. He looks forward to 2006 with plans for better experimental design with guarded optimism that he is on the track of a viable treatment for this disease.
In the meantime, Agri-Fos for Phytophthora-caused beech cankers, applied either as a bark drench or injected directly into the trunks of trees has been approved by the EPA and the NYS Department of Environmental Conservation. Other phosphorous acid formulations also approved for Phytophthora on beech include Arborfor, Whippet, and Alude. So far as Dr. Hudler is aware, data to indicate that any of these materials is effective for control of bleeding cankers has yet to be published in a scientific forum but their use in New York State for this purpose is now legal, nonetheless.
The bottom line is that if you are caring for European beech trees with bleeding cankers, Dr. Hudler's very tentative observation is that one of the phosphorous acid products may be a viable option for slowing canker growth. The earlier that cankers are found, the more likely you will be to contain them, and treatment is likely to be most effective when trees are actively growing. He has not seen any evidence of phytotoxicity on beech, but if the bark drench mix of Agri-Fos gets on herbaceous plants or moss, it will burn or kill the plants. If there are valuable groundcovers around trees you are treating with this material, be sure to cover them with a tarp during application.
Submitted by Paul Trader, Cornell Cooperative Extension of Rockland County
From Branching Out, Cornell University, October 2005
