I recently planted a small orchard of dwarf apple trees. In order to
limit both vole and borer damage I made little screen skirts with foam
collars for the trees, as I have seen described in a couple of
locations. My question is, with M9 rootstock being highly susceptible
to burr knots as it is, am I asking for trouble by having the foam in
contact with the tree essentially year round? The foam seems to dry
out but it will still always be dark underneath it. These collars are
approximately 18" off the ground, so they are not grabbing the
rootstock but rather the scion. Does anyone have any experience or
thoughts on this?