Q: Our deck is in the shade of a big tulip tree. This past week this tree as been raining down large splats of something all over the deck. We think it might be scale insects that suck the juice from tree with the resulting nasty shower.

A: Your diagnosis could be correct! Scale insects do suck sap from plants and they do exude copious amounts of honeydew. It could also be caused by a big population of aphids. Systemic insecticides will control either insect. Look for products that contain either imidacloprid or acetamiprid.