Ian Stocks responds by email:

"I think probably Diaspidiotus juglansregiae, which is recorded from many conifers, even though Juglans is the walnut genus; it is probably a cryptic species complex anyway. Another possibility is Nuculaspis*, which I understand to be another troublesome genus.

I can certainly slide mount the females if you would like to send samples.

Also, Dr Ben Normark, molecular systematists at UMass, might like to sequence specimens, especially of Nuculaspis, if that’s what it is.

*NB-To my knowledge, this is the only bona fide correct use of the root-form ‘nucu(l)-‘ instead of the root-form ‘nucl-‘ to convey ‘nuclear’; thus, ‘nucular’-in some linguistic universe-may technically be correct, but for the wrong reasons."