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.