What can be sprayed on pine trees to keep deer from eating them?

Answer

The deer were there first. We as humans moved in on there habitat.

But enough of that, try going to a homegraden center and ask them for some kind of repellent or try moth balls around the base. You can always put human hair clippings around to keep them out but if they are really hungry, nothing can stop them but a good hunter. Good luck.

more try spraying it with chilli.

You might want to go to a hardware store or nursary and ask for coyote urine. It comes as a dried powder. Spread on the ground around the plants and the deer will stay away (the urine tells them that a predator is around and they might be the next meal !).