During the first summer after bark grafting a pecan tree, I try to return to that graft every three weeks or so. In April, I showed you how I
make a bark graft. By May, the buds on the scion were
bursting with growth. Then in June, I selected the strongest growing bud to become the
central leader and later that same month I
pruned off stalked buds. Now its mid July and I'm back again (graft in photo at right) for some more graft maintenance.
The graft has continued to grow in height but has begun to slow down in response to this summer's dry weather. With a slower rate of growth, the newest part of the shoot is not producing stalked buds. However, I did take the time to add another tie to attach the graft to the 2x2 post.
In the past, I've seen a new bark graft become the home to a colony of ants (photo at left). Ants like to live in the warm, moist environment found under the aluminum foil and plastic bag that covers the graft union. Ants tunnel into decaying wood found on the upper portion of the stock and weaken the graft union. To combat possible ant problems, I decided to take a bold step and change my normal graft aftercare procedure this summer.
Lets start by unwrapping the bark graft (photo at right). The first thing I noticed under the wraps was the dark, wet stain located on the top of the stock near the scion. This is
bacterial wetwood starting the decay process on the stump of the stock. Opening up the wound to the air will dry up this wetwood and slow the decay process.
The second thing I noticed was that callus tissue has formed all the way around the outside ring of the stock, a sign of healthy growth. I also noticed that lenticels on portions of the bark that had been covered by plastic were expanded (lenticels are raised rough patches in the bark that allow stems to "breath").
Removing the grafting wraps at this time of year would help prevent ant problems but exposing the graft union to full sun in mid-July would cause major sun burn problems. So I decided to apply some sun block in the form of white tree marking paint (photo at left). We have used white latex house paint in the past to protect graft unions but I couldn't resist the convenience of using a spray can with a paint specifically tested for non-toxicity to trees.
In applying the paint I covered all areas of the graft that had once been covered with aluminum foil and plastic (photo at right). Now, the ants can't find a cozy place to lay eggs and I have a bright white visual marker to the location of my grafts.
I have used tree marking paint in the past and found that it fades rather quickly. This is probably not a problem in terms of providing sun protection for the rest of this summer but if you would like to have a more permanent marker of graft location, latex house paint will give you 3-5 years of service.
