Yes spalted wood commonly is prone to tear-out.  Sometimes sanding is the only way to get a good surface.  Many times you can stabilize the wood prior to your final cuts:  water, shellac or sanding sealers can all work.   I frequently use water based poly on spalted wood.  It is "water white"  meaning very clear, with none of the amber tones added by oil based finishes.  It tends to have a high solids content & has a pore-filling effect.  So if the tear out is particularly troublesome(ie, can't be removed with normal tool work or sanding), I might dry sand a piece to 220 grit, coat with poly, wait anywhere from 2 hours to overnight, and then sand with the next highest grit.  Any tear-out that remains after the 220 sanding tends to get filled with poly.   Repeat up through 400 grit, followed by Beall buffing.     This produces a very glossy finish.   If I want a semi-gloss finish, I would probably wet sand with walnut oil through 400 grit.  This would fill all the pores and tearout but the piece will be darkened by the oil:  still looks good but the spalted contrast is muted somewhat.  Leave as-is for a matte finish or buff to a semigloss.

Keith Marshall wrote on Jan 4^th, 2018 at 11:59am:

I would suggest that before you need to employ one of Mike's suggested method you try "shear" scraping or high angle cutting with the wing of a gouge.
If you are using a scraper flat on the rest it can have a tendency pull fibers out rather than cut or slice through them. This will be especially evident when using "suspect" wood. I would describe this as wood that is either punky, spalted or has less than uniform stability throughout.
A high angle cut can drastically lessen or eliminate tear out in some circumstances.
As always, a photo would also help us help you.

Keith, there are a number of 'it depends' issues here. First, spalting is a process where fungi start turning good solid wood into compost. So, how far the spalting goes can make a big difference in how clean the wood will cut. The particular type of maple can also make a big difference. So, sugar maple/hard maple will be way different than big leaf maple which is a lot softer.

Next comes your cutting. A scraping cut, for a finish cut, works pretty well in end grain cutting, but not in side grain/bowl grain cutting. Again, softer woods are generally worse than harder woods. This leaves high angle shear cuts, which means the closer to vertical the cutting edge is, the better the cut is at gently lifting the wood grain and slicing rather than pulling it out. I have a video up in that section here which is all about shear scraping (a non bevel rubbing cut). You can do bevel rubbing cuts as well. On the outside of the bowl, to get the higher shear angle, you generally drop the handle of your gouge. This generally doesn't work as well on the inside of the bowl because every thing gets in the way, bowl rim, tool rest, and lathe bed. If I am doing a bevel rubbing shear cut on the inside I prefer a gouge with a ) shape nose (Doug Thompson's fluteless gouge or some thing similar) as it is easy to roll over on the side with the handle slightly dropped. This profile also has a larger sweet spot than the standard bowl gouges.I have found that particularly with softer woods, if you sharpen on a 600 grit wheel or hone, and take very light cuts, that can make a big difference.

The other alternative, especially if the wood is really soft, is to 'stabilize' it. Methods vary from polymer impregnating (vacuum pot, pressure cooker, and heat), to flooding it with Cactus Juice, super glue, or even spray lacquer. Some times just getting the surface damp (not soaking wet) and taking very light cuts will do a better job.

Of course, there is no limit to the 'toys' you can buy to help you out... I do have a bunch of bowl turning videos up...

robo hippy

One of the tremendous benefits of this forum is that when appropriate you will get all of the possible solutions to a problem.  Sometimes one works, sometimes another, so it's a benefit to know the possibilities.  You'll also hopefully get explanations so that you can grow as a woodturner. 

Hope the range of responses wasn't overwhelming.