Peach borers are moths - apple borers are beetles. One excellent site to dive deep into borer nuance comes from Art Agnello who puts out an excellent IPM newsletter for Cornell. Check out this issue: http://www.nysaes.cornell.edu/ent/scafolds/2000/7.24_insects.html
I've always been amazed to have never seen an adult borer though I've dealt ruthlessly with hundreds of the larvae when probing their tunnels. Window screening works best to protect young trees. The bottom edge needs to be buried an inch or two in the soil. The top is folded/tucked rather snug around the girth of a tender treeling and held that way with regular paper-type staples. I make it a spring-task to go along to each tree to loosen overly-tight screening (due to the previous year's growth) and staple it snugly anew. I'm also finding a very thick coat of kaolin clay applied to the bottom foot of more mature trees and dribbled thickly against the soil line seems to serve well. This coating is applied in late June and renewed a month later . . . but again, the window screen is a surer method and protects against vole damage. Adult borers fly to each tree and crawl down the trunk to get to the preferred egg-laying site at soil line. Which is why many conventional insecticides help reduce if not eliminate an infestation. Eggs are laid between early July through August here in far northern New Hampshire.
Heartsong Farm Healing Herbs
Lost Nation Orchard
RFD 1 Box 275
Groveton, NH 03582