We have just received this enquiry from Dave Barden on our Facebook Page and thought readers may find it helpful in identifying early stages of black spot on a bonsai. His tree is a Chinese Elm. Please click on this link if you would like to see the conversation: http://www.facebook.com/BonsaiDirect?sk=messages_inbox&action=read&tid=id.100919306728855
Hope you don’t mind me mailing you, I have a Chinese elm about 8 yrs old, been growing well, pruned nicely etc, this past week / fortnight alot of its leaves are going yellow and dropping off, can you tell me why or give me any advice please. this is quite new to me ive had the tree about 4 months and its been ok up until now.
Dave has also sent us some photos.
Hi Dave, thanks for the photos. I believe this is one of 2 things.
It is most likely to be the early stages of black spot ( a fungus). The spores are in the air and Chinese Elms are susceptible. It is easily treated, you can buy a fungicide which treats for black spot and spray ASAP and again a week later. I would then use it once a month as a preventive measure. We spray weekly as a precautionary measure.
The only other thing it could be is red spider mite (but I cannot see any signs of very fine webbing or leaves which are hanging off the branches).
Both black spot and red spider mite show the mottling of the leaves as in your photos in the early stages; this is why I am slightly unsure.
I hope this helps,
all the best