Get it right at planting
Some Geneva rootstocks have tolerance to replant disease.
To achieve a yield of 50 to 70 bins per acre, the canopy of a new orchard must be established by the third season after planting, says Tom Auvil.
Photo by Geraldine Warner
A wrong decision at planting is something a grower has to live with for the life of the orchard, warns Tom Auvil, horticulturist with the Washington Tree Fruit Research Commission.
“You can never make up lost time if you make an error when you plant,” he said during the Washington State Horticultural Association’s annual meeting. “Make sure you do every planting right.”
The yield benchmark is 50 to 70 bins per acre for a new apple orchard in Washington, with 1,200 to 1,500 trees per acre on Malling 9 and a vertical system. To accomplish this, 80 percent of the canopy must be grown during the first two seasons after planting, and the whole canopy must be established within three seasons.
The rootstock has a relatively small impact on vegetative growth in the nonbearing phase of orchard development because the genetics for precocity do not limit the overall performance of a vegetative, nonbearing tree, Auvil said. So, it is still possible to grow the full canopy in three years, even with a dwarfing rootstock and weak scion. The rootstock does have an effect on the spur and crop density—which translates to how many fruit per foot of branch the tree can support. Good and consistent cropping is needed for an apple tree to calm down and be reasonably productive.
Rootstocks can influence fruit size, but it’s sometimes difficult to distinguish from the effect of crop load. If the trees set a big crop but the fruit is small, the grower might mistakenly attribute the fruit size to the rootstock.
“If you look at fruit numbers versus size over time, what we want is large fruit with more fruit per tree in that same period,” Auvil said.
Annual cropping is one of the greatest economic drivers in apple production, he said, and biennial bearing—with 50 bins per acre one year and 15 the next— is one of the greatest economic disasters a grower can encounter. The more dwarfing the rootstock, the more regular the cropping.
One of the main obstacles to good orchard establishment is replant disease, which will require mitigation whenever an orchard or vineyard is replaced with another woody perennial crop.
Some of the new Geneva rootstocks, which are resistant to fireblight, also have tolerance to replant disease. The rootstock alone will not provide complete mitigation for replant disease, but could be a benefit where fumigation fails or where it is not legally possible to fumigate.
Horticultural management is intertwined with the rootstock traits, Auvil said. Semidwarfing rootstocks put growers at a tremendous disadvantage because the trees don’t crop annually.
Trees on Budagovsky 118 will produce fruit that is two box sizes smaller than trees on dwarfing rootstocks. “So, if you’re growing Gala on Bud.118, you can expect to have a big crop of Gala size 125s every other year,” he warned.
Malling 106 and M.111 don’t crop annually, produce smaller fruit, and have no tolerance to replant disease, Auvil said. Those two rootstocks have been used successfully for spur Red Delicious, but cannot be used when replanting. “If you put them into a replant site, you will fail, I would say, 80 percent of the time.”
He describes M.7 as a noxious weed. “It’s better than seedling, but 30 percent of the trees, if you don’t trellis them, will fall over. Semidwarfing trees are not a substitute for fumigating and planting precocious dwarf rootstocks. There’s no point in being in tree fruit production if you’re going to grow 15 to 20 bins per acre,” he stressed. “It’s not going to work.”
Malling 9: There are more than 100 clones of M.9 in Europe. It has become the global standard, and though it has some resistance to root rot, it is not tolerant of replant disease. Trees on M.9 are 25 to 50 percent the size of seedling, depending on the clone. M.9 337 is midpoint; Fleuren 56 is smaller; and EMLA, Nic.29, and Pajam 2 are larger. Nic.29 seems to have trouble calming down and produces root suckers. All the clones are bigger than M.26 in Washington State and give better annual production.
Malling 26: It is a myth that M.26 is more vigorous than M.9. This will very rarely be the case on a replant site. M.26 is one of the most inconsistent rootstocks in terms of vigor, and there can be a variance of two to three feet in growth from tree to tree. It is susceptible to fireblight, prone to biennial bearing, and performs poorly in replant sites.
Mark: Mark is the current standard for precocity. Auvil said more than one operation in Washington has trees on Mark that produce 140 bins per acre of Granny Smith. It is a good option for plant-in-place orchards because it takes budding and grafting very well and the trees grow uniformly. The trees grow very vigorously at first, but once they come into bearing and set fruit, they stop. The trees must be completely grown before they crop. The rootstock’s characteristic root proliferation at the soil line has not been an issue when growing trees from bench grafts.
Budagovsky 9: This is a widely available fireblight-resistant rootstock that propagates well. However, it is sensitive to replant disease, and the trees will be smaller than on Mark. In a number of orchards in Washington’s Columbia Basin, Gala and Fuji trees have not filled their space when planted four feet apart. They need to be planted more densely on this rootstock.
Geneva 11: This rootstock is the size of the M.9 337 clone and is very productive. It is not tolerant of replant disease but still yields better than M.9 in replant sites. It is resistant to fireblight and crown rot, and is fairly winter hardy.
Geneva 41: This rootstock has good horticultural characteristics. It will tolerate replant disease but yields best in fumigated sites. It is winter hardy.
Geneva 214: This rootstock, which is bigger than G.41, has done well in Washington State. It is resistant to fireblight, woolly apple aphid, and crown rot and is winter hardy.
Geneva 935: In Washington, this rootstock is no bigger than the bigger M.9 clones. It is not resistant to woolly apple aphid.
Geneva 16: The major shortcoming of this rootstock is its hypersensitivity to viruses. It is M.9 in size and is fireblight resistant.
Geneva 202: This woolly-apple-aphid-resistant rootstock was released in New Zealand several years ago. It is also resistant to fireblight, but its tolerance to replant disease is not yet known. It doesn’t have the best crop density, and Auvil said it is not productive enough for him to recommend. Yields might be 20 percent less than with G.41.
Geneva 202, 935, and 16 are the most readily available of the Geneva rootstocks.