Disastrous results from using pruning sealers and wax

[Peng]

I would like to share some of my results of using pruning sealers and wax on several types of trees and the bad results I noticed.

I’m new to growing fruit trees. This year I planted many fruit trees and applied wax/sealant after pruning them in spring. The pruning was done to get the desired shapes I wanted for the trees (e.g. open vase for plum and peaches and KGB for cherries). I used 3 products - beeswax, tree wound dressing, and pruning sealer.

Until recently, I noticed that many of them did not heal well and some were even producing brown sap. So I decided to scrape off the wax/sealant on top of the pruning cuts. I noticed a lot of black/pink discoloration on the xylem part of the wood. Several cherry branches were producing sap/gummosis, and one plum branch was also producing sap as well.

These two pictures show gummosis after I cut off the top part of this branch. You can see the discoloration going through the xylem. Does anyone know what caused this?

After removing the top of the branch, the remaining wood still has this discoloration.

Worried about an infection, I decided to cut down more of the wood until a clean surface was revealed.

However, when I bought this 4-in-1 pluot tree, the nursery used another type of sealant on it (a head cut on the rootstock/interstem). This sealing material produced less discoloration and no gummosis. When I scraped it off (please ignore the beeswax I had applied on top of their sealant), the wood underneath looked aged light brown and smooth.

This picture shows the yellow material the nursery had put on. It is definitely not the beeswax or black wound dressings I used. It is yellow and elastic - almost like silicone/latex/rubber. I’m very intrigued as to why this material worked better on this plum tree, whereas the ones I used produced some kind of dark-colored infections deep into the wood, even gummosis.

This picture shows the surface after the nursery’s yellow sealant was removed. One noticeable difference - when I removed their sealant, I also cleaned out their phloem, and the phloem was green, indicating immediately underneath this nursery’s sealant, the phloem was alive, whereas the phloem was dead or rotting under the beeswax/other two types wound dressings I used. I’m puzzled. How did their silicone-like sealant produce such a different result? And I notice a mulberry tree from another nursery also used this type of sealant (and the same yellow color too!). Please see the picture below:

On a European plum tree, I had also applied beeswax on all of the pruning/heading cuts. I decided to remove all of them.

This branch looked horrible after I removed the top 1/2" of it, including the wax. So I decided to remove more but also collect the next 1" of wood and cut it apart vertically to reveal the inside.

So I obtained this section.

This is the vertical cross-section view. It shows the development of this discoloration. I do not know if it is some sort of fungus. But it clearly dug into the xylem of this branch.

This is the top view of the left half.

I proceeded to remove any discolored wood until I could not see any more dark discoloration. However, there are some trees that I couldn’t go much further because cutting further would seriously impact the branches on the trunk.

[Peng]

Another branch on the European plum tree. This is after I had removed the wax + the section below the wax. Removed all the way down to a branching point. It is still showing discoloration. Should I continue to remove it until I see no discoloration?

[Peng]

Also, this wood cracked after I removed the nursery’s sealant. Should I be worried about this crack? Water would most likely seep in.

[Peng]

I did not take pictures of the cherries. But they look similar to the plum pictures and also showing signs of gummosis.

Interestingly, pears and apples were less affected.

Cherries looked the worst, then plums and peaches.

I could not have thought this would happen. Because I live in Seattle and spring is wet here. I covered each heading pruning cut (especially on the trunk) with wax/sealant thinking I’d protect the trees from rainwater. Interestingly, the cuts I did not apply sealant did not develop this.

[marknmt]

I don’t have answers, but I think you did a great job setting this up for discussion. I’m looking forward to learning more here. Thanks for the excellent photos and descriptions.

[tbg9b]

I don’t like pruning stonefruit during our wet PNW weather. I also know using pruning sealant isn’t recommended much these days, (unlike the past). When I needed to do my heading cuts on my stonnefruit trees early this year I waited for a forecast window with at least 3 or 4 dry days to minimize the chances of infection. I quickly did my heading cuts during the dry weather then immediately sealed the cuts. On the smaller cuts I mostly gave a quick shot of black pruning spray paint to quickly seal things up. On some the larger cuts I used this yellowy colored sealant I purchased off of Amazon:

https://www.amazon.ca/gp/product/B091F2XKXK/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

I had no issues with any of my heading cuts becoming infected.

Did you sterilize your tools prior to performing your cuts?

[danzeb]

I never use sealers when pruning. Healing is better without them.

[Richard]

I use Morrison’s Tree Seal on large cuts (2"+). Also, I use it on smaller cuts (~1") when disease is a concern. Neither of these occur frequently. I never remove sealant after applying it. It can take years for scar tissue to grow underneath before the sealant falls off or is integrated into the tree bark.

[tbg9b]

@danzeb

I never use sealers when pruning. Healing is better without them.

That is the modern view, however living in the coastal PNW we often see many months of almost continuous rain. When heading cuts need to be done on stone fruit trees during the monsoon season sealant is a good precaution against the diseases stone fruit are especially susceptible to. Pears and apples I don’t worry as much about during the rainy seasons. During the dry weather with hot temperatures and low humidity I never bother with sealants on pruning cuts. Some extra precautions seem only prudent when dealing with stone fruit trees during wet disease spreading periods.

[danzeb]

Here’s a quote concerning disease: “While research supporting this advice is sketchy at best, it may be justifiable to use a fungicide or insecticide during spring or summer pruning. If pruning is done during the dormant season, the chance of infection is greatly reduced and wound treatment should be avoided.”

wound-sealer.pdf

[Richard]

@danzeb

If pruning is done during the dormant season, the chance of infection is greatly reduced

… depending on disease pressure and climate.

Overall though, it is very good information. I liked this statement:

It’s important to recognize that trees do not heal. Instead, they isolate damage through formation of
suberized, lignified wood that physically and chemically repels invasion. Callus develops at the edge of the wound and gradually expands towards the center. This wound wood remains for the life of the tree; bark does not regenerate itself the same way our skin does.

[swincher]

I’ve used buddy tape/parafilm with good results for a few types of trees that I have pruned during the Seattle wet season. I’ve never tried any liquid or spray products.

[tbg9b]

@swincher

I’ve never tried any liquid or spray products.

You must not be a grey beard then, old dogs / new tricks.

:white_hair:

[alan]

The research against sealants is quite old, really. and well established by Alex Shigo, who I think got lots wrong, but this one pretty much right. He also started a cult of arborists opposed to topping trees because the results are terrible if you don’t steer following growth at the cuts- he never once suggested that the problems of topping can often, if not usually, be alleviated by training a tree to a single dominant leader afterwards, or just making the removal of upward shoots a regular part of maintenance, as we fruit growers usually do. He was also adamantly opposed to stimulating tree growth with supplementary nitrogen, even young trees. In other words, his beliefs often spilled over the banks of genuine research.

But the research he did was mostly financed by the U.S. government to invent a pruning compound that works, and he failed to do that but did figure out how trees heal wounds, which, in itself, makes him a god of tree science. Pruning compounds can keep wounds wetter, which can encourage rot.

However, for grafted scion wood the largest issue is usually for the scion to gain water flow from the tree before it dries out, so some kind of sealant may greatly increase the odds of healing before death by dehydration. I’m not sure the sealants are the problem in these photos so much as that the bark of the scions were not protected from dehydration. That is why I wrap scions with Buddy Tape parafilm.

Pears and apples have more resistant bark to dehydration and you can get good rates of success with only a dab of sealant on the tip, but not so with stone fruit- at least in my region.

[danzeb]

Also its important to not to cut the branch collar at the trunk.

[Peng]

Did you try this yellow sealant on cherry trees? They seem to be prone to gummosis.

Yes I do sterilize with rubbing alcohol.

[Peng]

Thank you for your tips! I do need to clarify that there are no scions or grafting in these photos. I pruned the trees according to KGB or open vase shapes and used wax or wound dressings to seal the open tips or trunk. This was done this spring. Recently I started to check the sites and found that some were leaking sap, which got me to remove them and want to find out how they healed or if there was some kind of infection taking place underneath. Nearly all sites, when exposed, were showing discoloration running down the xylem.

[tbg9b]

Yes I did try it on heading cuts on at least 8 Cherry trees, they were fine with it.

[Peng]

@tbg9b @alan @danzeb @swincher

What is your take on this one? This is a fresh cut but the inside is already discolored. Should I continue to prune it down?

[tbg9b]

@Peng

This was done this spring

I did my heading cuts on my cherry trees during dormancy, likely early Jan. The buds on the cherry trees started swelling very early with the warm weather we had in Jan & Feb this year.

I did get some leakage initially on an apricot tree I headed and grafted onto in March. The sap was flooding my cleft grafts as this was not a good time & temp for grafting apricot. One graft on the apricot failed, but another elephant heart plum graft on the tree did well. The graft wounds and heading cut on the apricot tree all healed nicely. It actually responded super well to my heading cut and pushed a bunch of new scaffolds to make a perfect open center tree. I used that yellow grafting sealant on all my large cleft grafts this year, (brushed on top of the parafilm wrap). That combination seemed to work very well for me. That sealant I linked does not dry soft and pliable, it hardens, but is easily removed from grafts once they have healed.