Dropping needles are a sign your Christmas tree is dry. You can combat this by buying the freshest tree possible in the first place. Then, be sure to cut a slice off the bottom of the trunk immediately before you put it into the tree stand. This removes the sap that has collected over the original cut, which allows the tree to take up water. Make sure it has LOTS of water for the first couple days, and don’t ever allow it the water to drop below the cut. You can also spray your tree with Christmas tree spray before decorating it. That will seal the surface of the needles and keep them from losing moisture.