Prune it off... it wont hurt your tree... as for digging, it is quite possible that you could cut it out with a nursery spade and transplant it... With most trees it would be too late to dig... but crabs are pretty tough... (and who cares... its a sucker) however if you do transplant the sucker chances are it won't be a prarifire crab... it will be whatever generic malus root system your prarifire was grafted to...

Thanks for your reply. The sucker comes up from the ground so I'll have to dig it with a spade and sever it. I'm glad to hear it won't hurt my crab. What exactly is a "generic Malus root system"? Would it be foolish to plant it?

Malus is a crabapple... most cultivars of ornamental trees are genetic mutations which are continuously propagated or in this case... grafted. since specific characteristics of these cultivars cannot be reproduced by seed they are propagated from cuttings off of the "mother plant" by grafting the cutting of the original plant onto a standard compatible crabapple trunk... on most suckers produced by grafted trees you'll notice a difference in the foliage shape or color... these are leaves produced below the graft on the donor root system...

Crabapples are notorious for foliage disease problems. They are carefully bred to produce cultivars that are resistant to these diseases. Prairefire is a good cultivar. I would not want a 'generic' crabapple on my property.

When cutting off your suckers try to prune them all the way down to the root they are growing from, but know that you can't always do that.

Also the more the tree is pruned (from the top), the more suckers it will produce. Although I think it will produce suckers regardless.

Be prepared to continuously prune suckers! It gets worse the older the tree gets. I have two crabapples and I usually do one a year. You get used to seeing them, but just don't let them get out of control.

Thanks Wendyb,
I guess I'll forget about planting it then. I will also keep a better eye on these young trees and prune the suckers before they get this big again.
Thanks again
Chris

Chris,
You could transplant the sucker, and graft/bud it using material from your Prairiefire to produce a clone of your original - or if you have friends with a different variety that you like, you can build one of those.
I pull/prune some suckers from beneath my apples; some I just discard, but some I line out in nursery rows and topwork to desirable named-varieties.

Grafting is not rocket surgery - just simple carpentry, and you don't have to have expensive equipment. A stiff-bladed boxcutter or exacto knife, a rubber band, or even just some masking tape is about all you'd have to have to get the job done.
But, be forwarned - it can become an obsession