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.