Mailing 9 rootstocks are too susceptible to f ireblight. Within the next two years, Cornell University plant pathologist Herb Aldwinckle hopes scientists and the tree fruit nurseries will have solved the problems of propagating Cornell's Geneva 41 root-stock—because, he thinks, that rootstock, and maybe others, is the answer to the problems of Mailing 9. Mailing 9 dwarfs trees to the size that growlers want, but the rootstock is susceptible to fireblight infection and to replant disease. Fireblightis an especially severe threat in the Midwest, Northeast, and Mid-Atlantic areas, and replant disease is a major headache in the Pacific Northwest. G.41, which is resistant to both diseases and the size of the medium-sized clones of M.9, could be the solution across the apple-production regions of North America, perhaps the world. Budagovsky 9, as a root-stock, is also resistant to fireblight, but it is not as good horticulturally as G.41 or M.9, Dr. Aldwinckle said.
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