Bonsai Chinese Elm dropping leaves

Question

I received a Bonsai Chinese Elm as a gift in Dec. It was doing great for about 3 weeks when it started losing leaves. I discovered aphids and something making webs. I used a commercial insecticide, Safe Guard containing Pyrethrins 0.02% and Piperonyl Butoxide 0.20%. Two weeks later many of the leaves have yellowed and have mottled look similar to apple leaf rust. Now I’m keeping the infected leaves cleaned up and hoping for the best.

Answer 1

It sounds like you have spider mites. The pesticide you used may not be effective against mites. I would recommend that you treat the tree with neem oil, if you can find it. It is often sold in hardware stores as “fruit tree spray”. Check the label. Neem oil is both a pesticide and a miticide. If you cannot find neem oil, look for a product that specifically says it is effective against mites.

The mottled look is from the mites sucking the nutrients out of the plant and should clear up when the mites are taken care of.

Answer 2

Jeff, I realize I’m a couple of years late to your query but for others with a similar question I can offer some of the ‘tricks’ I’ve learned in my 26+ years of raising {& killing Bonsais}. For spider mites, they HATE humidity, so a ‘trick’ I’ve learned is to spray them heavily with a solution of Tea Tree Oil & water {just a drop or two of the Tea Tree Oil to a quart of water!}
The Tea Tree Oil works in two ways. As an oil, it ‘sticks’ to the leaves & thus suffocates the little leaf sucking bastards! Next step it to ISOLATE the plant from your others & put a clear plastic bag over all for a few days!
That will both prevent further contamination & retain the spider mite hating humidity!
Best wishes to all with their beautiful “Tree in a Pot” as the word Bonsai {pronounced Bone-Sigh} is literally translated to!
If anyone else has any questions about this Art Form, please feel free to contact me!