I have had the same problem a couple of years ago when it was very cold with snaow on the ground I bought some capilliary matting that is used to sit oots on I coated the outside with ordinary engine grease which you can buy in a tin I then wrapped the matting around the bare area taking it a few inches above the bare area and just below ground level with the graease face outside. I secured it by wrapping thin nylon rope around the trees at about 100mm intervals
I then gave the matting a good soaking from above I did not put grease on the top or bottm edges of the matting The idea is to repalce the cappilliary action of the bark and stop the outer layer of the wood drying out Rain water running down the tree seems to keep the matting moist and the grease prevenst it losing moisture through evaporation
It has worked because the tree had teh same ammount of fruit hat year and in subsequent years
On the other hand I ma have just been lucky!