Bramley Apple tree grease band

[Holly Daze]

Arghhh! Put grease band on tree a couple of years back and thought perhaps I should remove it yesterday. Well, underneath was dark brown trunk with fungusy stuff. Doesn’t smell. Have I broken it? It has not fruited particularly well but I thought this was because it was getting established. Has lots of lovely blossom this year though. Any advice would be appreciated. By the way, I have a Grenadier cooking apple tree and every year it produces kilos of apples.