Answer: I don't know of any diseases common to Myoporum, and your description of the problem sounds more like an insect infestation than a disease. The silvery, or stippled appearance of leaves usually indicates the presence of mites. They are very tiny, andthe black spots on the undersides of your leaves are quite possibly adult mites. Why not try looking a leaf with an magnifying glass? Sometimes mites spin webbing, so that's a clue. If your plants do have mites, you have several options. Sometimes mites can be controlled by simply spraying plants daily--mites like hot, dry conditions--and a spray of water can wash them off leaves. You can also try an insecticidal soap. Read the label and apply according to directions.
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