The suckers are due to the rootstock to which the variety is grafted. I share your problem. Most herbicides that will kill the suckers can kill the tree, but there are products that are touted to stop suckers (google "tree sucker stopper"). I have found that physically ripping them out of the ground when small seems to stifle them longer than cutting, although they continue to return.

Good luck...

hortster

I used Sucker Stopper this year for the first time on my Crabapple. It worked. When you cut them (or pull them) first time in the Spring, you follow with the Sucker Stopper over the area they grew at. I did not have to do it again this year and I normally prune or pull them around 5 times a year. It has to be repeated each Spring at the first cutting though.
Cher

Cher, notice any changes in growth or fruiting? I would be watching next year's flowering, too. Just curious as those products contain growth inhibitors and if nothing else is affected by them I'm going to have to try it.

hortster

Hey horster. This year it flowered beautifully, but I know that was buds from last year and it actually flowers before suckers start and of course lots of fruit from those flowers but again first year using it.

I will say it did a LOT of width growth this year to give that definite fat Crab look and I'll actually need to prune some end of Winter as some are in the way of mowing. That's the reason I posted this was my first year using it. If someone remembers to ask me this time next year, I'll be more than happy to give further updates to you to see if next year affects more than what I've seen this year. I sure hope it is a product I can continue to use.
Cher

What is so hard about cutting the suckers off?

I did that and I got enough of the rootS to plant several as whole trees in the woods. Deer love apples.

Maybe not as good as the "suckerstopper" mentioned above, but two other chemistries that can work: Fatty acids like the old "Sharpshooter" herbicide that Safers used to market-I don't know what's become of that, and another class of "burn down" herbicides like stuff containing diquat. These and the soap act to burn the foliage of whatever they're applied to so they don't translocate into the roots, etc. Probably best used when suckers are just starting. I used to spray Sharpshooter on some amelanchiers that were supposed to be tree-form but were doing what amelanchiers want to do everywhere-form a thicket. It worked but then you had a cluster of tiny dead suckers to look at at the base of each tree.

+oM

Thanks all, off to buy sucker stopper!