Question

Diseased Hoya   QUESTION: Hi Melissa,
I have a lovely old hoya - around 30 years old, I think - but its leaves are looking really terrible. I don't know what's wrong with it, but despite the condition of the leaves, it's producing more flowers than ever before. I've attached a couple of photos showing how bad some of the leaves are at the end of the branch, and the less marked leaves near where the plant emerges from the soil. In February this year all the leaves were green, though a few had a white patch that looked like it'd dried out. There was nothing like this mottled brown which is on nearly all the plant now. It's been in the same pot for years and years and we moved to where we are February last year. It's seemed very happy where we are now because I've never seen so many flowers on it before. Yesterday I had to repot it because the pot disintegrated. It's summer here in Melbourne, Australia, and we've had a lot more rain since the drought has broken. The extra water in winter and spring is about all I can think of, although the pot it was in was so old it hardly retained the water. Can you help???
Many thanks,
Lyn

ANSWER: Dear Lyn, Yes, I'm sure that the increased rainfall is the underlying source of the problem.  Hoya is one of those plants that prefer to completely dry out between watering, so the more frequent rain has made your plant more susceptible to a leaf spot fungus.  The solution is to purchase a fungicide (systemic if possible) for your Hoya and spray thoroughly.  I'm not sure what fungicides are available in your area, but in this case I would go with the strongest one available, perhaps daconil if available.  You will have to spray and/or saturate the soil more than once, likely many times, approximately every 1 to 2 weeks, for several months, but the condition should clear.  You are beginning this treatment in early summer, so you should have quite a few months for the plant to acquire new, healthy leaves.  Interestingly old broken pots that don't seem to hold water can often have soggy patches in them that stay wet for long periods and that makes the problem worse.  With it's recent repotting and a fungicidal treatment, your Hoya should be fine.  Congratulations on having such a magnificent plant (I love Hoya) and good luck in controlling the disease.  Please let me know if you have further questions.  Good luck, Melissa

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QUESTION: Hello again Melissa,
It just occured to me, after re-reading your reply, what should I do once the new healthy leaves appear? Should I cut off the old diseased ones? I often wondered if I should cut the whole thing back and get it to start again (ouch!) but am reluctant to do that, especially with so many flowers on it.
Thanks again, Lyn

Answer
Dear Lyn, Definitely do not cut the hoya back.  The fungus affects leaves only, the stem won't be harmed.  As the new leaves appear, I might start gradually removing the oldest leaves.  Don't make any radical changes.  Once a great deal of healthy full leaves appear, you could remove all the spotted leaves.  Until then, keep using the fungicide at regular intervals. Also remember, unhappy plants don't flower profusely as this seems to be doing.  It's mostly a cosmetic problem when caught fairly early.  Melissa