I have a backyard orchard with perhaps 15 plums and a scattering of other stone and pome fruits. One of my plum trees has developed a bad case of bacterial canker, which showed up this spring as many dead shoots (crisp brown leaves with gummy sap) throughout the canopy. I removed the affected shoots, of course, but what I want to know is whether the tree is systemically affected. I want to take bud wood from it to graft onto another tree, in case I lose that tree. Or I might decide to cut that tree down, as it never really performs well anyway… Either way, I want to preserve the the variety in my orchard as a pollenizer. Is it advisable to take healthy-looking scions or bud sticks from a tree with bacterial canker? (Frankly, I feel relatively certain that all or most of my stone fruit trees have some degree of canker already, as they exhibit shothole leaves during summertime…but I don’t want to totally blow it and spread the disease to a healthy tree.)
A related (or at least similar) question: another of my plums has had black knot lesions (or whatever those knobs are called). Am I correct in thinking that black knot is indeed systemic and one should NOT take scions or bud sticks from an infected tree?
And, heck, while we’re here, what about scab-infected and/or rust-infected pome fruit trees? Safe to take scions from those?
I’m no horticulturalist, so this is only anecdotal. I bud grafted multiple rootstocks with Dapple Dandy taken from a bacterial canker infected multi graft Apricot tree last summer. One of the 4 main scaffolds from this canker infected multi graft tree up and died last summer. I decided I was going to try and salvage DD from this tree before it died or I removed it, as it was my only remaining live branch of Dapple Dandy.
I bud grafted 4 different root stocks with bud wood from a DD scaffold from the infected tree last summer. I knew there was a possibility that I could end up spreading the disease so, I did not mult-graft onto a plum tree that was already maturing and healthy. I simply grafted onto young rootstocks that didn’t already have desirable varieties I was looking to grow. I figured no great loss if the tree showed signs of infection after grafting from an infected tree.
One of the DD buds I grafted was to Peach rootstock, and so far it is exrememely healthy looking and vigorous. It put on about 3 feet of growth late last summer after the grafted bud broke. It has put on another 3 feet of growth so far this summer, (late July). This bud grafted tree is one of my most healthy looking trees in my nursery, so IMO the attempt at salvaging DD from an infected tree appears to have been very successful. Other rootstocks I grafted last year with DD aren’t as vigorous as the tree in the picture below, but they are doing fine.
So, IMO as long as you aren’t harvesting scion wood from a branch close to the canker showing no sign of infection you may be fine.
Definitely don’t multi-graft from an infected tree to a heathy tree just to be safe. I harvest most of my rootstocks from root suckers, so I really have no worries if a graft doesn’t work out. Nothing wagered nothing gained IMO, as the DD variety is not easy to come by in Western Canada.
Also IMO, as long as you don’t harvest wood directly from a branch infected with black knot I think you’ll be OK. Just make sure it’s not collected from anywhere close to a branch that is/was infected with black knot.
As always nothing in life is a sure thing, and YMMV.
If you collect scion wood from a tree you are concerned about, dip the cut ends of the scion wood in wax. After the wax dries you can soak the scion wood in a solution of water with 10% bleach if your worried about black know spores on the wood you collect.
