that looks more like rust then something eating it - at least in this picture

Hard to tell in the image..certainly not deer, they take the whole tender tip and leave a ragged raw end on the twig.

Separately (sorry for the unsolicited advice but..), We are getting into the season for round headed apple borer damage here in VT, which can take out a young tree left unchecked.

I would make a point of clearing the weeds from the base of the tree and take off the protector. It just gives the beetles a nice safe place to hide and lay the eggs and then hides the signs of grub damage until too late.

Thanks to both. Sorry the photo isn't better quality. I'll do some research on rust and round headed apple borer.

Rob, the unsolicited advice is more than welcome! I'm a complete novice, so the more the merrier. I left the protectors on because the wretched rabbits gnaw on bark, but I could cage them with wire the way I did my dogwoods if it turns out to be a problem.

Is there anything else I should do about apple borers? I just want the trees to have a decent shot at getting established this year!

There is an insecticide known as lorsban that is supposed to be extremely effective. We keep our trees organically, so I have not used it myself, but I have come close after losing some trees and I think there is a place for it's use even in an organic orchard early in the tree's life when it is most susceptible. There are folks on this forum who can advise on it's proper use.

Without the use synthetics, you are basically down to keeping a sharp lookout. The adult beetles (which I have never seen) lay eggs in the trunk usually from soil line to about 1' up. They supposedly prefer some shelter while doing this, so keeping weeds and grass down around the trunk and plastic guards off helps some. (open wire is a better alternative if your dealing with summer bark eaters).

A lot of folks also recommend painting the trunk in white latex paint. From my experience it does nothing to discourage the egg laying, but it does make it much easier to spot the purple brown ooze and frass (shavings/poop) the grubs make as they girdle your tree.

Check carefully 2-3 times in the summer. If you see signs of damage use a sharp knife and dig out the borers. they will be in the cambium. start where the frass is coming out and remove all the dead tissue until you find good green cambium again...keep chasing it out until you find the grub. It feels like you are girdling the tree yourself, but the damage is already done and will get worse if you don't kill them. If you find one there are almost always a few more so look hard.

Like all pests, some locations have a harder time than others...maybe you will be lucky.