So far, only GRIN wood and Maple Valley orchard wood has proven to be virus free. Fedco trees, CRFG exchanges and Botner all appear to be sources of infected wood. CRFG is by far the worst offender, which makes me seriously question if I would consider grafting wood from CRFG exchanges without knowing where it came from.

It's really worth paying a little extra to get clean wood.

I know, your knife is out allot,...I found out, the more you graft onto one tree the more it is prone the get infected.

For those with a lot of varieties, an advantage of the close hedgerow plantings as opposed to the n-way graft is you can check the spread of these diseases - nearly all of the spread is through trees with more than one variety on them.

Scott

Scott, the apple virus is the same, it expresses itself under stress. On many varieties, it never even shows, the only way to know if the wood is infected is by grafting an indicator variety to it. Granny Smith and golden delicious are two varieties that are highly susceptible and will show symptoms.

My approach is to use kelp spray mixed with serenade to boost the immune system of the apple trees. The kelp provides required micro-nutrients and the Bacillus subtilis in serenade is also known to stimulate the natural immune response of plants. It won't get rid of the virus, but the plants are less affected.

The virus removal process is straight forward but time consuming. Here is the process:

• Year 1) Graft infected wood onto a potted rootstock
  
• Year 2) Place growing tree into controlled heated environment to keep the tree at a constant 38C temperature for 8 days.
  
• Year 2 + 1 or 2 months) take fresh budwood and graft onto virus free rootstock. (In the professional procedure, the fresh budwood is collected right after the heat treatment and then grown in-vitro via micro-culture. The reason is that fresh growth is usually virus free. So the combined heat treatment plus immediate fresh growth collection ensures a high rate of success of virus removal.)
  
• Year 3) Let graft grow out and observe to make sure the virus was successfully inactivated by grafting indicator variety.
  

If the virus was not successfully inactivated, repeat procedure. This procedure is worth it if you have an old unique heirloom and you want to make it available to everyone.

Now, keep in mind, most people who do exchange scions have Franken-trees. This does significantly increase the chances of virus infected wood to circulate. There is the possibility to heat treat wood before you graft it but it would work only on summer budwood, Winter wood would start to bud out and no longer be graftable. Of course, there is the possibility of collecting and heat treating the wood right after a late Fall leaf drop. Since the wood has not yet been chilled, it would not bud out at that time.

Note: heating your in-ground tree to 38C for two weeks won't work. The roots also have the virus. However, if you have super-dwarf trees, you can dig them up and go though this procedure on the tree itself.

One more note on viruses. I did have an interesting discussion with the fellow who runs Tress of Antiquity. He tells me that people did remove the viruses out of cox orange pippin, but the resulting wood after the in-vitro procedure resulted in a cox orange pippin that produced inferior tasting apples. So either the in vitro process caused a mutation, or the viruses actually contribute to improved flavor in the fruit. So virus removal isn't always a good thing. In some cases, you might prefer the virus infected version.

I can already see it: "Scotts Virus removal service" - will show up with bulldozer and will tent your tree on location to heat treat. :) LOL

Scott

What is the probability that my trees have the virus? Do orchardists ever destroy their trees just on the outside chance that they are infected? That would be really sad.

Marc

Speaking of scion wood exchange, i got a pigeonnet rouge from you a couple of years ago, and it's got leaves that are red when they emerge, and they slowly turn dark green, more akin of a red fleshed apple. However, the pigeonnet rouge from Geneva does not have red leaves. Anything red fleshed growing close to your pigeonnet rouge that could have been sent to me by mistake?

Scott

Scott

All grafting runs the risk of introducing viruses, especially when people do multi-varietal grafts. So for example you could have a nice virus free lapins cherry, and do a couple of grafts of some older varieties that might have viruses. Then you decide to exchange scion wood of your lapins cherry. Et voila, now an infected lapins cherry is in the scion exchange flow.

Bottom line is that grafting often leads to virus infections, the only way is to stick with known virus free sources.

I got scion wood there 2 years ago. It was my first time grafting to established trees. The only graft that actually worked (and produced a misshapen apple) was Mutsu. I was discouraged (some of the grafts grew but later died), so I skipped last year. I am attaching a photo of my only success so far, 2 year old Mutsu graft's only fruit. (Grafted to a Granny Smith)

Now I want to try again. I guess I will just take my chances and hope for the best. Thanks for the info though. I never would have thought that. I am going to the one at Cabrillo Hort in Aptos CA.