I have just started gardening. My first tree purchase was a Yoshino Cherry (Prunus y yedoensis Ivensii). After potting it into a larger pot, it has started to have lots of holes appear in the leaves. I have found 1 leaf with a collection of bugs on it but no idea what they are or how to treat it.
I am in East Lothian, Scotland if that helps.
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Update Image from tips of branches, believed to be new growth but could be a symptom.