most of the time when they send you a nasty letter that you have to clean up your yard its a neighbor that complained...at least that is what i understand...but in your case 40 acres sounds like they could have just been checking the area...it was great when my neighbor had to clean up all thier scotchbroom...they had other stuff growing in it...it was the best summer breathing i had that year...i have since moved but didnt realize it was my breathing problem...:)