Will grinding the stump of an infested tree affect the rest of the trees in yard. Also, will it be safe to use the mulch from the stump grindings in gardening?
The grinding of the stump will take care of the beetles in that stump.
You can use the grindings in your garden as a mulch. No more than an 2-3 inches deep and as with all mulches, pulled away from contact with plant stems, crowns and trunks.