Thanks to everyone for your helpful -- and diverse! -- responses to how best to handle treating tree cores to prevent spreading decay. As suggested, I've removed the identifying information and combined the answers here as a compiled reference for all. The responses are from Jim Worrall, Dave Houston, Matteo Garbelotto, Brian Geils, Kevin Smith, Martin MacKenzie, Linda Chalker-Scott.
I'm afraid the clear message is that there is still not a clear message for how to handle this. We'll do our best in this project to follow impacts and report back what we find.
Thanks to all!
Greg Gilbet
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Below are some references, and of course there are lots more. The evidence does suggest that wound treatments/disinfectants are likely to be ineffective or harmful.
Although foresters often replace cores after examining them, with the idea it will prevent entry of insects and pathogens, at least one paper has shown that plugs are deleterious. That makes sense because they may interfere with wound closure at the cambium, prevent drying, and provide substrate for buildup of inoculum in the hole before invading the wound.
I’m not aware of a paper showing that sterilization of borers and bark surface reduces infection, but it can’t hurt. Carrying bits of infected wood from one tree to another certainly provides more inoculum potential than a spore. If there is concern by managers, it seems a logical thing to do.
One paper in the list below (Weber) concludes that boring into a decay column does not result in long-term expansion of the decay column, but of course that could vary with tree species.
Unfortunately, there are lots of published examples of increment borer wounds leading to disease, so it is difficult to assure people that it won’t.
Berry FH. 1978. Decay associated with borer wounds in living oaks. Broomall, PA. Research Note NE-268. 2 p.
Clark FB. 1966. Notes and observations: Increment borers cause serious degrade in black walnut. Journal of Forestry 64(12):814-814.
Dujesiefken D, Rhaesa A, Eckstein D, Stobbe H. 1999. Tree wound reactions of differently treated boreholes. Journal of Arboriculture 25(3):113-123.
Hepting GH, Roth ER, Sleeth B. 1949. Discolorations and decay from increment borings. Journal of Forestry 47(5):366-370.
Houston DR. 1971. Discoloration and decay in red maple and yellow birch: reduction through wound treatment. Forest Science 17(4):402-406.
Kessler KJ, Jr. 1974. An apparent symbiosis between Fusarium fungi and ambrosia beetles causes canker on black walnut stems. Plant Disease Reporter 58(11):1044-1047.
Lorenz RC. 1944. Discolorations and decay resulting from increment borings in hardwoods. Journal of Forestry 42(1):37-43.
McQuilkin WE. 1950. Effects of some growth regulators and dressings on the healing of tree wounds. Journal of Forestry 48(9):423-428.
Weber K, Mattheck C. 2006. The effects of excessive drilling diagnosis on decay propagation in trees. Trees - Structure and Function 20(2):224-228.
You may have found this study that quantifies, for one tree species, the efficiency of decay detection by this method.
Stenlid J, Wästerlund I. 1986. Estimating the frequency of stem rot in Picea abies using an increment borer. Scandinavian Journal of Forest Research 1(1-4):303-308.
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Gregory, for what it is worth, you might check out an ancient pub. of mine that looked at what happened to yellow birch and red maple increment borer wounds treated with various substances. The upshot was that discoloration and decay readily occurred if nothing was done to the wounds, and that various chemicals affected the extent of these consequences in different ways in the different species. The substances which reduced discoloration and decay the most were those that blocked the entrance of air and which had little to no effect on wound closure.
(Houston, D.R. 1971. “Discoloration and Decay in red maple and yellow birch: reduction through wound treatment”, Forest Science 17 (4): 402-406.)
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the main issues arise when the hole is freshly drilled. An
application of a fungicide without tarring or sealing will ensure
most fungi will not take hold for a few days while allowing the wound
to dry. A dry wound is much less susceptible and you will get , as
you know, a few decay fungi that may use it as infection court, but
overall not many.
I suggest apply a fungicide after you drill the hole and do not seal.
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I am not the source for information to address your question, but I can make to suggestions. 1) the USDA Forest Service Forest Products Lab at Madison, WI and 2) the Tree Ring Lab at the University of Arizona, Tucson, AZ. I don’t know who at either place would be the best contact, but that knowledgeable person may not be on the Forpath list.
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This topic is frequently discussed and occasionally even directly investigated by the dendrochronology community. You might want to search the archives of the International Tree Ring Database Forum for past discussions and references. The forum and its archives are linked to: <http://web.utk.edu/~grissino/forum.htm>. I give the above reference to past discussions on the topic because there are definitely different points of view.
Here is my point of view as a pathologist and dendrochronologist that occasionally dissects trees with deep wound caused by increment borers:
1. How important is the information to be gained? Obviously, this is a judgment call. I discourage increment boring as a class project. It can provide information useful to forest research and management. For me, the choice is less about comparing the effects of increment boring to no injury and more about comparing the relative value of collecting increment cores versus stem disks.
2. Less injury results from coring healthy, vigorous trees than declining trees. Reduced injury results from better compartmentalization of infection and decay on the inside and more rapid closure of the wound.
3. Do not treat the borer wound. Disinfection even if possible would last only a very brief time. Disinfecting agents (bleach, alcohol, etc.) will kill living wood, bark, and cambial cells near the wound. There is likely no value in plugging the hole with dowels, wax, etc. That can obstruct closure of the wound by the formation of new wood.
4. Use sharp tools, both to save your back and shoulders (or motorized power head) and to provide a cleanly cut wound.
5. Disinfection of the borer between trees is likely not necessary *except* with a small set of diseases such as, perhaps, fire blight. There are lots of differences of opinion here. My view is that inoculum of wood-inhabiting fungi is ubiquitous, particularly the insect-vectored sort, so host response is more important than pathogen exclusion.
6. Keep in mind that boring may release previously compartmentalized, well-develop decay infections in the core of the tree that can then be released by mechanically breaching that boundary with the borer.
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As I have been asked the same question more than once, and still do not have an answer I would be interested in what you find out. Can I ask you to compile the responses you get and send it to all of those who respond. In the past when I have used this mailing list , I made a compiled response removed all identifying E-mail addresses and sent the compilation to all who responded. This way each respondent can recognize her/is response and see what unnamed others thought.
My thoughts are. (!) slight down slope on core to prevent filling with water.
(!!) fill hole with a non-biodegradable plastic core, cut flush with the surface. Rationale, as hardwood will seal over the hole eventually and the circular closing of callus tissue from opposite sides will conflict at the centre. Fill the hole with inert sterile plastic rod and we get that conflict in the first year of growth. So all we have bought with the plug is that the hole is sealed over at time zero. But then again if the tree’s natural growth rate is such that the hole would be closed in one growing season would we gain anything?
(!!!) Document your results on subsequent decay and publish it so that others who have to subsequently have to answer the same question have a substantiated source to quote.
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Attached is a summary put together by John Pronos, retired Plant Pathologist with USDA Forest Service Forest Health Protection (California). It does not address tropical trees but has been helpful over the years for answering this question.
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Like you, I’ve not found a lot on what, if anything, to do with the holes from coring. My inclination would be to treat the corer like we do pruning tools – sterilize with Lysol or some similar household disinfectant (not bleach!), let dry, then core. The argument would be that pruning like coring can introduce pathogens, but sterilized tools all but negate that possibility. Pruning wounds also take longer to seal and open up more living tissue than corers do. For your project, it would be especially important since your core samples will likely be contaminated with fungi.