trail cameras rune... thats what works. call your local Sheriff's office and file a report of trespassing. and then put up trail cameras. that way you can take cold hard evidence to the LE agency.
gates also work...until someone cuts them down
oh, and so does sharpened rebar at say a 45% angle in the areas you know they are coming in on your land. make them have to buy new tires
, but that may start a "war"... so i have to fall back on what i said first. TRAIL CAMERAS