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European Fruit Magazine

Good results with CG.11 in Haidegg

Is M.9 still the most suitable rootstock for apple trees? Not under all conditions. This may be concluded from the trials with new rootstocks that were done at the research station in Haidegg (Austria). Researcher Thomas Rühmer discussed the trials during the online Bundeskernobstseminar of 10 through 12 January this year.

Throughout Europe, M.9 is by far the most commonly used rootstock. New rootstocks introduced in the past, such as the Polish P-, the Russian B- or the Czech J-TE series, often turned out not to be the ideal replacement for M.9. Times have changed, however. New training systems are under development, trees are more and more often planted in the same place as their grubbed predecessors and susceptibility to diseases plays an ever more important role. Also for organic growing or for weak-growing varieties, (think of SQ159/Natyra®/Magic Star®) a slightly stronger rootstock than M.9 may be valuable.

M.9 not always ideal
“M.9 is a good rootstock, however: trees on M.9 do not stay upright of their own accord, but have to be supported and the rootstock is susceptible to fire blight, woolly apple aphid, winter frost and replant disease”, Rühmer enumerated. Woolly apple aphid preferably hibernates on the rootstock, where burr-knots offer ideal conditions for the woolly apple aphid. Fire blight can also be found on or in the rootstock and is much more difficult to find there than in shoots or flower clusters in the crown of the tree.
As the second important reason to look out for another rootstock, Rühmer mentioned the development in the direction of trees with more central leaders, such as the Bibaum, Guyot or Flagtree. For this type of tree shapes and the accompanying training systems, M.9 is probably not always the most suitable rootstock, but a slightly stronger rootstock may be advisable.

Read the article in the may-edition of EFM