Looks to be lecanium scale. No sense treating until the crawlers (babies) emerge from the "shells," then use an ultrafine horticultural oil spray. I don't know where you live, but if you're familiar with growing degree days, they usually emerge somewhere between 700-800 GDD. Here in Wisconsin, that's usually sometime in July.
Good luck!
Suzy, Zone 5, Wisconsin
I just saw these bugs in a plum tree in my garden. They look like tiny,
> black, German army helmets. The tree is not doing too well this year,
> with a lot of dead branches, and the critters all over. What are they
> and how do I get rid of them? Thanks.
>
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