QA Forum

Question & Answer

We are discussing Gardening, Growing and Green Thumbs!
With Brian Walters, Diana O'Brien and Pauline Cornish

Question:
I planted a Yellow Top Ash (Eucalyptus luehmanniana) five or six years ago on Sydney's northern beaches. Some of the leaves have a red/yellow/rust appearance which I think may be red spider mite. I haven't noticed it on the local bush mallees. I assume those leaves are permanently damaged. Can I prevent this happening. (Brian's response)

Answer:
Brian - There are a number of possible causes of this sort of leaf damage and red spider mite is one. Other possibilities include nutrient problems, adverse weather conditions, particularly extended dry periods, and fungal disease. Without a positive identification it's difficult to recommend a specific treatment. Mites can usually be identified by the fine webbing they create under the leaves.

If you are certain that mites are the cause, then there are several approaches. If the tree is not too large, a strong jet of water from a hose will often dislodge them - it may be necessary to do this over a period of several weeks as mites multiply rapidly and you're unlikely to remove them all at the first attempt. Of course, you will need to be mindful of water restrictions currently applying.

Overall, however, most eucalypts develop some discoloured leaves and this is often not a cause for concern. If the plant is otherwise healthy, it's probably best to leave it alone.

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