Question
The oak tree in my back yard produce a great deal of sack and is very messy and dirty how do i prevent this tree from producing sap? Do u have someone in the Calabasas, Calif area that can help me with this.  This tree is a protected tree

Answer
More than likely the tree has an infestation of either aphids or scale insect. Both of these will suck the plant juices from the tree and secrete a substance called honeydew which is high in sugar content and sticky. Control the insects and the sap will stop. Treat the tree with an insecticide called Bayer Advanced Tree and Scrub Insect Control. Apply this to the soil around the tree and the roots will transport it to the foliage and twigs and the insect will be killed when they suck the plant juices. It will take a week or so for the action to get to the foliage after you apply the insecticide. Check with your local nursery for this product. Here is a web link to the product.

http://www.bayeradvanced.com/product/Tree-Shrub-Insect-Control/concentrate.html