I came across this article from 2022 Modern apple rootstocks evaluated in Mid-Atlantic - Fruit Growers News where growers are stating that “Bud 9 and Bud 10 work well when growing bitter pit-susceptible varieties such as Honeycrisp”, “The Bud 9, Bud 10 seem to be a really good combination for Honeycrisp, Evercrisp, Jonagold – any of those bitter pit-prone varieties”.
It’s hard for me to comprehend how rootstock can address calcium deficiency which is a suspected source of bitter pit. Does anyone have experience with such a combo?
He also says to remove fruit entirely the first 3-4 years and is talking about a 10-12ft high-density “fruiting wall” system. The whole thing was just anecdotes with the growers saying you need to try different rootstock out and figure out what actually works at your site. They didn’t mention if they were using foliar or soil amendments of calcium, or just letting the trees get well established before fruiting, or go into much other detail. Another guy swore by G.11 and presumably would have mentioned if all his Honeycrisp were unmarketable.
Anecdotally, I can say that the more vigorous the tree, regardless of rootstock, the greater the problem with bitter pit and that it may be partially related to very large fruit. I find it helpful to thin whole clusters in spring to the spacing where you want single apples but to not thin the clusters until about 3 weeks before harvest or at least not before August here in NY. The remaining apples will receive more calcium (maybe) and certainly won’t be so big. It also seems to improve brix levels because so much of the sugar is stored into the fruit in the few weeks prior to ripeness. For home growers, it also assures choosing the best, unscarred apples.
I’m just another grower with opinions, but they are based on pretty close observation, the kind of observation that growers of commercial orchards often don’t make simply because of the scale of their operations. Many hire other people to do the pruning and other field work and don’t even touch their trees.
Maybe that’s why I get more useful information from this forum than I ever did from magazines like Goodfruit Grower.
If you’re putting in a commercial orchard I think you really need to do a test plot. This is especially true for high density systems which are not very forgiving and the margin for error is low. You can do quite a bit of research to narrow down the choices that may work but you really can’t say what will work for sure in advance. So the best choice to put in a test plot with a bunch of cultivar/rootstock combinations and see what works for you on you’re ground.
Here’s a good read on bitter pit and rootstocks topic, not a scientific publication (yet) but something supported by trial data - " Half-baked research: Honeycrisp bitter pit and rootstocks, 2019 & 2020" by Jon Clements.