Conference pear

 I have a twenty year old Conference pear tree which produces a very good
crop. This year is no exception, but about 10% of the leaves have some sort
of disease. On the affected leaves an orange spot about ¼" across appears on
the top side and underneath a yellow blister apparently containing about
three eggs or what appears to be eggs.
What is it, and how do I get rid of it, if not for this year perhaps next?
Alistair

 
"Alistair Macdonald"  wrote

That sounds like a Gall Wasp, the sort of thing that is common on Oak trees.
I don't know of one affecting Pears but these wasps usually have a two year
life cycle and in some cases they climb up the trunk from a period in the
ground, so a grease band should prevent it if it's that type and a Tar Oil
spray in winter would kill any overwintering eggs/pests and certainly do no
harm.

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Regards
Bob H
17mls W. of London.UK

 Thanks Bob,
That sounds like it and the remedy noted.
Alistair

 
"Alistair Macdonald"  wrote

A word of warning, Tar Oil Winter Wash is excellent but nasty stuff so wear
cloths you wouldn't mind throwing away, keep skin covered, wear eye
protection and if you have evergreen plants under the tree cover them or it
will damage them. Won't harm the dormant tree though.

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Regards
Bob H
17mls W. of London.UK