Apple Tree Canker

Frank just sent me some pictures of canker on his apple trees.

Canker is a fungal infection that often infects apple trees and I think other fruit trees as well.  I did a post on this a few days ago.  What I understand is the infection tends to enter the tree through open wounds, as well as the scars left behind when leaves come off the tree in the fall.

First Frank gives three examples of canker at progressively worse stages on different trees:

This last picture is what Frank uses as an example here to show how he treats it, and he pointed out that this is not really that bad.  The yellow-green stuff you see in the picture is lichen and unrelated to the canker infection.

In a comment on my previous post, Frank mentioned you should never cut more than half way through a branch or the tree trunk.

Here I’ve already started to clean up the wound, use a sharp knife, a chisel, drawknife, or whatever you like to work with, as long as it’s sharp.

In the next picture, the wound has been cleaned up, the brown patch in the middle is actually the ‘true’ apple wood, the white wood surrounding it is ‘spint’, the new wood that hasn’t turned into real wood already.

Here the wood has been treated with the tree paste, obviously something is wrong with it, this should give a smooth result (I suspect the tree paste has been frozen this winter), instead of the sort of bubbly aspect it gives now. This is a method I learned over ten years ago, nowadays many tree pastes are based not on a sealing aspect, but on a breathing aspect, and are mostly oil-based. These new products are indeed better, but I don’t know if in this specific case the oil-based pastes would work as good as the older-style ones.

It’s interesting Frank mentioning the changing composition of tree paste.  Since making my last post I’ve been reading a little bit about this on the Internet.  It seems the older tree pastes were mostly asphalt or latex like materials, but many people concluded they were not only on the toxic side but trees were able to heal their wounds faster without them. I remember using these kinds of pastes in my family when I was a child.

This seems to go along with Søren’s suggestion in my last post that I could also just leave the canker alone and let it kill the tree slowly.  If the canker infection enters the tree through open wounds, and you conclude it’s best not to use tree paste, than I could also see why you wouldn’t want to create a wound by cutting a spot of canker away.  Perhaps this is also what Frank was referring to when he mentioned the older sealing style tree pastes might work better in this case.

I recently read a recipe for home made organic tree paste made with equal parts of sand, clay and manure (one place suggested this should be composted first).  This will clearly wash away, and need to be reapplied after rain.

I am completely undecided as to what to do.  Does anyone else have any experiences or suggestions?