I am planning expanding my hobby cider apple orchard. I have read that many of the late blooming, classic English varieties are very susceptible to Fire Blight. Is there an advantage to graft placement? Normally the graft is a few inches to a foot above the crown of the roots. What about growing out the rootstock for a year or even two, establishing frame work branches and then topworking the tree? Would this provide a buffer between one branch and another, or will the infection simply travel throughout the tree and infect the susceptible varieties?
This process would be done on the Geneva 935 rootstock, first to provide Fire Blight resistant rootstock, and secondly to provide increased production on unproductive varieties.
If there is a patent on Geneva 935 (?) there might be a good starting point to answer your question. If you can see one then try covering related patents listed in that patent for other experimental data.
One thing I can remember about firelight is that fast lush growing conditions such as high nitrogen application fertilizing favors fireblight. If the 935 is controlling the rate of growing to your new apples then grafting higher might make sense if it's stated that way. In which case making a long interstem would also work.
Another mode of action to "block" the disease would be more idealistic if the patent mentions it, then you can still leaf feed fertilize above the graft with less concern it will spread and kill the root. (ie. start over)
Can you find a link and tell us where you are?
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