Take the 2-minute tour ×
Gardening & Landscaping Stack Exchange is a question and answer site for gardeners and landscapers. It's 100% free, no registration required.

My Cussonia bonsai suffers for a couple of months now from an unrecognized pest. First I thought these are mites, so I bought a powder that you mix with water and spray on the leaves. But unfortunately it persists. It looks like brown spots on the back of the leaves, and some leaves are getting white spots all over,

Does anyone know what pest is it according to the images? (I could add only two since I'm a new user) And if it mites, perhaps I should spray weekly or monthly?

http://i.stack.imgur.com/snqd6.jpg

http://i.stack.imgur.com/w8rqO.jpg

share|improve this question

2 Answers 2

up vote 3 down vote accepted

The Cussonia or cabbage tree is native to South Africa and used for bonsai due to the large fleshy roots. It likes a well drained neutral pH soil with lots of sun.

The pictures are helpful but do not show the white spots that you mention. What I do see is:

  • veins of the leaf remain green but the area in between is yellow.
  • it appears that new growth is affected more than old growth

This looks more like an iron or manganese deficiency, due to the pH of the soil being too alkaline, rather than a pest issue.

It is still possible that you have spider mites but we would need to see a closeup picture of the underside of the leaf where they live. Full details on what spider mites look and control like are found here but, in brief, they look like tiny grains of salt and are found on the undersides of the leaves where the flow of sap is strongest (near the veins). A really bad infestation will show webbing between the axils of the leaves. Fortunately a dish cloth soaked in soap and water rubbed on the underside of each leaf repeated three times at 5 to 7 day intervals will offer good or complete control.

Here is what you could try:

  • An application(s) of a sulphate or "acid" fertilizer will help.
  • Watering with pH neutral water helps in the long run.
  • Top dressing with a more acidic soil based on peat moss or sphagnum moss helps too.
share|improve this answer
    
First of all thank you for the thorough answer. I will try what was suggested. Could you advise with what should appear on the back of the leaves if these are indeed mites? –  user1895 Jan 31 '13 at 15:29

Just to update on this issue in case someone stumbles upon it: I did add the moss. However, the method that worked the best was to re-pot it in the same pot. I had this bonsai for more than two years, and as the roots are overgrowing the size of the pot, there is no space for the roots to suck water anymore.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.