How do I choose plum and apricot rootstocks?
Answer: Because of the prevalence of soil-borne diseases, the selection of disease-resistant or disease-tolerant rootstocks for plums and apricots can be important. Size-controlling rootstocks (dwarfing rootstocks) can also be advantageous to the grower trying to reduce or eliminate synthetic pesticides because: 1) a smaller tree can allow for better spray coverage with organic pesticides; and 2) smaller trees are more easily accommodated in high tunnels where the blowing rains that often spread disease can be eliminated.
Because many scion-root combinations are compatible within the genus Prunus, researchers and nurserymen have a lot to work with to find the best plum and apricot rootstocks for any given condition. For instance, Citation rootstock is a peach-plum hybrid developed by private breeder Floyd Zaiger. Citation produces a tree about three-quarters the size of a tree budded onto a standard seedling rootstock (e.g., Marianna or Myrobalan). Moreover, Citation is resistant to root-knot nematode and very tolerant of wet soils. It’s compatible with either plum or apricot and is probably the rootstock of choice for the plum X apricot hybrids.
If you’re looking for dependably dwarfing rootstocks for plum or apricot, Citation and the Krymsk series (Krymsk 1 for plums and Krymsk 9 for apricots) are probably the most reliable choices, and Citation should get the nod for most growers because of its broad disease resistance. The Krymsk series seem resistant to nematodes, but bacterial canker could still be a problem.
Standard seedling rootstocks are still widely used, especially in the part of the nursery trade geared to home growers. In most cases, these rootstocks will function well enough, but growers will need to avoid sites where plums, cherries, peaches, or apricots have grown before because of the chance of infection by nematodes, verticillium wilt, oak root wilt, and crown gall.
For sites where plant-parasitic nematodes are likely (sandy and/or where Prunus species have been planted before) or have actually been detected, rootstocks have been specifically developed for nematode resistance. These include Flordaguard, Nemaguard, and Nemared. In any case, if you’re considering planting on a commercial scale, it is advisable to contact state Cooperative Extension fruit specialists to see what rootstocks are recommended for your area.
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