Gum and wilt on grafted stone fruit trees
One of the new grafts on a multi graft I did this year has a gum residue at the graft site and the growing tips seem to be wilting. Is this a problem and, if it is, how should I treat it? The parent tree is an old nectarine, which was suffering from leaf curl. I have left 2 parent shoots to develop. The stump was sprayed with copper oxychloride prior to grafting (most of the old wood was removed in prep for the grafting) and any leaves of the parent which were showing signs of wilt have been removed as they appeared, and it now looks very healthy. Of the 12 grafts of 5 different varieties, I have managed 100% take!
Gummosis is the oozing sap from wounds or cankers on fruit trees.
Gummosis can result from environmental stresses, mechanical injury, disease or insects.
Cytospora canker or Valsa canker is the fungal cause of gummosis.
One of the symptoms is that new shoots or leaves will yellow and wilt.
The disease kills the wood underneath the canker.
These fungus diseases overwinter on dead wood and in the spring release spores, they transfer to the tree with water splash or wind.
They will enter the tree in open wounds (likely the graft site).
Here is a link with more information.