Question
I thought I had a Maple tree, but I have an Elm Tree, anyways we have lived here for 6 years and this is the 1st year it decided to sap.  I guess the aphids around town are horrible this year, everyone in towns tree is sapping.  Is there anything to do if the aphids are that bad? We live in Northwestern Montana.  Thanks Candi

Answer
For large trees it is hard to spray insecticides on the foliage so I would recommend using a systemic insecticide. These are taken up by the tree and transported into the leaves and twigs and when the aphids suck the plant juices it kills the aphids. Certain persistent insecticides that move systemically in the plant may provide control through the fall. Imidacloprid (Bayer Advanced Garden Tree and Shrub Insect Control) is a newly available systemic insecticide that can provide aphid control on trees for several months following application to the soil. Check with your local nursery/garden type store for this insecticide.