Problems with Olive Trees and Star Jasmine

My Star Jasmine has hundreds of small black mites (aphids?) custering around the buds, any ideas what I should do? Are they dangerous to the plant?
Also, my olive trees have a kind of white floss substance nestled between some of the leaves and stems. In the middle of the floss, there are small, lightly coloured organisms which I think are developing into small insects? Again, any ideas what these organisms are or what I should do?

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