Answer: Pittosporum tenuifolium requires well draining soils or the plants will become stressed which can lead to root rot. The foliage will take on a brown color and the plant will die completely. The spots you describe sound like a fungal or bacterial disease, which, if left untreated, can also cause death of the plants. Brown or black spots and patches may be either ragged or circular, with a water soaked or yellow-edged appearance. Insects, rain, dirty garden tools, or even people can help its spread.
To prevent and control, remove infected leaves when the plant is dry. Leaves that collect around the base of the plant should be raked up and disposed of. Avoid overhead irrigation if possible; water should be directed at soil level. For fungal leaf spots, use a fungicide as soon as you notice the problem. Be sure to apply according to label directions.
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