Is this mushroom or animal? I can remove the black dots by slightly scratching the leaves.
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possible duplicate of Can anyone identify this abnormality that is on my dwarf citrus? – kevinsky♦ Aug 23 '13 at 10:56
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@kevinsky: both are indeed certainly scale, eventhough it is not the same species. – RockScience Aug 23 '13 at 17:47
If you can remove them from the leave then they are scale. Due to the dark colour I believe they are Black Scale (Saissetia oleae). They suck juices from the plant and excrete a sugary sap. Look for sticky leaves. Ants are sometimes seen in close company with these pests.
For small plants some control can be done with soap and water but a complete answer is here.
They are described here and an excellent answer on maintenance of citrus is here
Edit @RockScience feels they are a different species of scale for which a reference can be found here. Either way soap and water and possibly a toothbrush for "hands on" pest control will work.
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thank you very much for your help. After some research based on your hint, it seems to be 'Parlatoria ziziphi', which is indeed a variety of black scale. The leaves are not really sticky but comparing my plant with pictures of this scale is clear. – RockScience Aug 23 '13 at 16:43
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