Are there circumstances where painting or sealing pruning cuts is still a good idea? i.e. larger cuts, fruit trees, springtime, conifers.

Reply to post by Greg Miller, on April 24, 2000 at 20:51:42:

First, what product are you talking about using? Something like orange shellac has at least been shown to have no negative effects, unlike creosote-based products.

If talking about orange shellac or some other demontrated neutral effect product, there are two uses that we recommend:

1) with clients who insist that the wound be covered, because they don't like the color or they just "know" that what is supposed to be done;\
2) when pruning live wood during a known period of high pathogenic activity; in the midwest, the USDA recommends using it against oak wilt when pruning in early to mid spring, and here we follow the Cornell (sorry!) pathologist George Hudler in suggesting it be used for live wood pruning in the early fall, when most decay fungi are sporulating.

It may be worth recalling that research shows that the fastest rate of wound sealing (so, presumably, the least infection) comes in the early spring, with high cambial activity, and the early summer, after full leaf expansion and before drought stress restricts photosynthesis.

Reply to post by Jerry Bond, on April 24, 2000 at 20:51:42:

Jerry, do you have citations on orange shellac? I brought it up recently in a thread on the ASCA listserver concerning treatment of wounds or scars created in root crown excavation.... it seemed a good idea to me before replacing soil.

I learned to use it in the "old days" of cavity work. The masters immediately coated any cut cambium surface to prevent dessication. There was some thought that the alcohol might be fungitoxic, but that was not the main intent... sealing was. I'm very comfortable from experience that it causes no damage but have not had references to cite.

Two other questions are 1) what's different about white and orange? 2) it's now marketed as "amber (formerly orange)." Has there been a formulation change from the original product and if so do the research data (if any) reflect this?

Scott

Reply to post by Scott Cullen, on April 24, 2000 at 22:09:03:

Originally made from lac, a substance secreted by the scale insect Laccifer (Coccus) lacca, and refined through heating and mixing with alcohol to a type of varnish. The base form is orange (less pure), but it can be bleached to clear (white). I suspect it is now made synthetically, but not really sure. Since it is a natural organic compound, it will be non-toxic to the trees (except perhaps for the alcohol or acetone solvents).

The purpose was (is?) to seal the fine pores with a solid coating of non-toxic material. The idea is to seal in moisture and prevent desication of tissues, and to prevent infection by micro organisms. I've never seen any studies on the reliability of this material, although I seem to recall Shigo as having discussed this with outher treatmetns. It may be in his early work on dressings.

Reply to post by Russ Carlson, on April 27, 2000 at 08:47:41:

I know from experience (and passed down wisdom) the anti-dessication part works.... if your QUICK. The old timers were fanatic about coating the bark edge around the excavation every few inches... even if it was likely to get cut back again in final shaping. They could point out places on older work where the bark edge had been dessicated or "popped" from the underlying wood.

The sealing out micros think intuitively makes sense, at least new ones that didn't get in from the air or cutting tool.

So do we guess that the difference between O & W was/is some damaging agent related to the bleaching?

Reply to post by Russ Carlson, on April 27, 2000 at 08:47:41:

Russ, I am currently dealing with trying to preserve the largest healthy Madrona (Arbutus menziesii) in WA state. We have major problems in the area with both "Nattrassia" and "Botryosphaeria/ Fusicoccum". It is necessary to prune some small lower branches from the tree and I am concerned that, irrespective of how well the pruning cuts are made, we will be creating wounds attractive to the above pathogens.Do you think orange shellac would be of any use in this situation? Is there anything which might reduce the likelihood of wound infection? Is "Borax" phytotoxic? if it can be used to stop invasion of "Annossus" on cut hemlock stumps might it work here?. Sure would appreciate any and all feedback,

James Causton.

Reply to post by James Causton, on April 27, 2000 at 23:29:02:

Please Send for me All comments about Nattrassia