Under the outer layers of bark on one of my Betula jacquemontii I yesterday
discovered some spongy patches. Exploration (peeling back the peeling
layers) revealed linear clusters of black mouldy domes 5mm dia, looking
rather like scale insects. further exploration revealed white wiggling worms
5-10mm long living in the domes.

10 minute on google suggested Bronze birch Beetle as the culprit, all the
descriptions and pictures fit with what I see.

I stripped off the overlying peeling bark on all I could see and sprayed
with ultimate bug killer

does anyone have any experience or advice?

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PK
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God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t,"
and there was light.