I have a five year old grapefruit tree grown from seed. I keep the tree outside in the summer (Vancouver) and bring it inside for the winter. This year (it is still outside), the leaves have been a much paler green than usual and in the last few weeks have become covered with a dark brown/black dusty fungus, covering most leaves and much of the stems. Any suggestions as to what is wrong and how I can treat it ? Thanks, John Bennett
What you're seeing could be sooty mold. Is the foliage sticky? If so, it could indicate the presence of sap sucking insects such as scale which would explain the yellowing of the leaves.
