Thanks all, especially Nina. I now see that my earlier diagnosis was
incorrect, definitely not crown gall, more like an aphid infestation
causing root galls.

I am now wondering if there's any link between these and a type of
woolly aphids that appear annually on the same apple trees. These orange
brown aphids with white fluff emerge from bark swellings near twig tips.
They appear to have overwintered beneath the bark. I usually deal with
these once a year with a Q tip and meths but they usually return the
following year.

Reading up on aphids has opened my eyes. Some do live in colonies inside
galls. Some in exceptionally large galls. Thankfully these don't occur
on apple!

Cheers

Kev Bailey
Vale Of Clwyd, North Wales

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