Question
Under 2" oval sections of bark on the limbs of the Macoun apple tree, I found a half-inch white grub in one spot and white powder or other stuff in others.  I also noticed spots on the tree where it looked like small tunnels or something is eating the wood.  On some branches there are older split areas, exposed to the core.  My question is how do I stop these guys and do I need to prune off the limbs where they hatched in previous years?

Also see it on the Gravenstein, but not the Yellow Transparent.

thanks

Answer
Sue,

This is some kind of wood borer, possibly a beetle. Most borers are not fatal for the tree and the best approach is to simply prune out the affected limbs. Since apples can tolerate a lot of pruning this should not be a problem. Late winter is a good time to prune apple trees before the sap starts to flow in the spring. Also, contact your local Cooperative Extension office and they will have a better idea of the exact borer species since this tends to vary with region.

Jack DeAngelis
http://www.livingwithbugs.com/