How much land do you have? Is the land fenced? And is there gates on it? It might be worth the money and fustration to get a good fence and gates up on the land. What I've learned from the past is Trespassers are creatures of habit. They use the same path in and out, and take the path of least resistance. Are they seeing deer from the roads and going in after them? If so maybe a screen of White Pines, spruces, or Hybrid Populars will stop the tempation.