Mesquite tree with sap running down from a pruning cut Q. This is about mesquite trees of which I have two in my front yard. Last fall I had both trees trimmed quite drastically by a recommended tree service. They are coming back very nicely except one limb is dripping what I thought was oil; a dark stain looking like oil or tar.              At first, I thought the gardeners had dripped oil over the rocks and over my lantern with their equipment.  Then I looked up!  I don’t know what to do about this; I clean up the area as best I can and within a week, it looks like it had never been cleaned. Is this something I should worry about, or should I just keep on cleaning?  Only one limb on one tree is doing this. A. Mesquite trees can bleed quite profusely when they have been cut. This is nothing to worry about and it should stop by now.             Out of curiosity you might just take your finger to this sap and smell it. If it has a strong yeasty smell and it attracts flies it’s possible it could be a relatively minor disease problem called Wetwood or slime flux. I just mention this because it is more of a curiosity than anything else.             There is really not much you can do about this disease and it should not have any long-lasting effects on the health of the plant. This is not true of this disease and a couple of others but mesquite it should be no problem. It is going to be unsightly.             If the liquid persists, it is possible to drill a hole at the bottom of where it is leaking and    tap in a 2 or 3 inch tube into the hole so that the liquid runs down and out the tube, not down the side of the tree. Make sure all is sterile when puncturing or putting a hole or cut into plants.