You may consider getting a seperate rootstock for the Asian pears. My pear tree with both Shin Li and Dasui Li is pretty balanced, but my Warren tree grows much more slowly. Easily outgrown by Potomac on the same tree. You may be able to prune it evenly, but expect to lose a lot of buds on the Asian pear branches, or the Warren may end up shaded out.
No FB on any of these yet in Southeastern Alabama.
Asian pears:
For fireblight resistant asian pear cultivars, my personal favorites are Kosui, Shin Li, Olympic/Korean Giant as first choice, followed by Kikusui and Ishiiwase as second choice.
As for rootstocks, Pyrus ussuriensis is extremely fireblight resistant, but unfortunately very susceptible to pear decline. Which rules it out for me.
Callery is pretty fireblight susceptible in my experience, as well as psylla and decline susceptible, which is also a no go for me.
Which leaves us with OHxF 97, Horner 4 & random BET seedlings for high vigor rootstock choices for asian pears. Because personally, I would never use OHxF 87 or smaller for asian pears, but then I also have a little adverse growing conditions.
OHxF 97 obviously has big advantages in regards to its fireblight and pear decline resistance.
Horner 4 has advantages when it comes to my arid summer climates (I’m in southern coastal OR where it literally doesn’t rain April-October), because their root systems are massive and deep, and they need a quarter of the irrigation that asian pears grafted onto OHxF 97 need.
We also have extreme winter storms of up to 100 mph, and even though both rootstocks have excellent anchorage, Horner 4’s anchorage is superior to OHxF 97.
As for fb and decline resistance, I haven’t seen either on Horner 4. The literature on this topic is limited. But since it came from OHxF genetically, and I haven’t seen any, I think Horner 4 is pretty safe when it comes to fb and decline.
Obviously BET is always a viable option for asian pears. It is psylla and decline resistant, with varying degrees of fireblight resistance. Highly vigorous, great anchorage, low irrigation needs.
The really biggest downside to BET for asian pears is that it suckers like a mothersucker. And I mean, constantly. Everywhere. And lets not forget that those suckers have nasty spines on them.
Which makes this rootstock a little challenging for the low maintenance oriented home orchard keeper. Because unless you are on it, you have yourself a problem.
Horner 4 barely suckers at all. Really only the occasional one. And there are no spines. Which is a huge plus.
I would say grafting compatibility is a bit lower for Horner 4 than for BET, when it comes to asian pears. Tree size and growth rate are comparable. Trees on Horner 4 tend to be more precocious than on BET.
Horner 4 does tend to get you bigger fruit size in asian pears than OHxF 97.
I think as of right now Horner 4 is the best high vigor, precocious, disease resistant rootstock option for asian pears. And for standard size euro pears, although there OHxF 97 has advantages in terms of yield efficiency, and those Horner 4 grafted euro pear trees really do get massive.
To me, to sum it up, Horner 4 is the new BET alternative that comes without the annoying suckers, and probably a more consistent fireblight resistance, while having the same advantages in regards to vigor, fruit size and reduced watering needs. And it doesn’t have the Callery disease issues. Callery is a fantastic asian pear rootstock - until all your trees die. Not worth the risk imo.
I should add that my above choices of fireblight resistant asian pear cultivars are very much flavor and texture driven. Which is why they are so limited. There are other fb resistant asian pears. They just either taste like crap, or they are mealy.
I like my asian pears crisp, sweet, tart. Not musky, fermented and grainy. I’m serious, some of them taste so bad you’ll spit them right back out. Call me picky, but eww.
Yield, vigor and fruit size also fall into my equation.
I know it’s a short list, but you are better off with 5 good cultivars than with 20 mediocre ones.
All 5 of those are on the japanese end of the flowering spectrum, so they overlap with each other as well as some of the early euro pears.
Ishiiwase is horrible acting as a pollinator. The rest are good. Kikusui is the only one on that list that is at least somewhat self fertile.
Have you grown Yoinashi?
FB magnet for me.