Depends what the actual problem is - could be Brown Rot, Apple sawfly, totrix moth infestation. Check the fruits for holes - often brown rot sets in after the fruit's been penetrated by a moth larvae or damaged by sawfly larvae. You need to decide on the problem before carrying out remedial/preventative treatment.

I'd say Brown Rot is very descriptive of the problem. The fruit goes from looking lovely to entirely rotten very quickly. Maybe a small patch to start with, but no holes. The brown mush is covered in tiny white pimples (smaller than a pinhead). The leaves also have a problem, some of them turning brown and curled up at the edges, but this seems to be a common problem with fruit trees in my garden and sometimes the pussy willow as well. Does this help in suggesting a treatment? Thanks for your input so far.

The leaves sound rather like my damson leaves where the problem was aphids. They have gone now but the damage remains. I have had good advice on here about what to do next year - one was to spray with a solution or organic washing up liquid and Crissue suggests a garlic treatment - see her blog about aphids. Oh, and Tugbrethil said to spread seaweed round the tree in early autumn (you can buy it at garden centres if you can't get to the coast)

That's interesting - my trees do get woolly aphids (and I do use washing up liquid on them) but I didn't know they were the cause of the leaves crinkling up and going brown. Thanks.

The thing about Brown Rot is, it can only get into the apple if there's some break in the skin - it's a fungal infection, and usually enters the apple through things like bird peck, codling moth holes, skin splits caused by irregular water supply or fungal scab infections. You need to work out what the cause was and minimise the risk of it recurring, and remove immediately any fruit showing early signs of brown rot. Any mummified fruit remaining on the tree should be cut off, including the spur directly behind it. All fallen apples should be cleared as quickly as possible, and should be disposed of away from the garden, or burnt. Clear away fallen leaves from beneath and around the tree before winter sets in.

I suppose it could be bird pecks, but it's a bit of a mystery to me as until the first brown patch the apple appears to be perfect. Where does Brown Rot come from - is it air borne? Or in the ground, or the tree itself? I've noticed there's quite a lot of moss around the base of the tree - any connection? There were only about a dozen apples in total and five have already gone, so it won't be difficult to keep an eye on the rest, and I'll cut off the spur as you suggest from now on.

Its a fungus in the air and ground - think of it as something like staphyloccus, which is present on most of us on the skin, but causes no trouble - unless it gets into a puncture or wound in the skin. Cut one of the apples open to make sure there's no tunnel inside from a caterpillar.

I see - thanks. No, there's no caterpillar. If it is the birds starting it off it seems I will have to hope for a crop so big that they can't get their beaks on all the apples before they're ripe!