Is it private property or is it BLM or state?
If it’s her property I would tell them to stay off.The property is private.So don’t trespass.
If she is leasing the property from the government she can do nothing.Afterall they’re the property owners.
Make sure it really is the USDA first.
Your friendly gov worker will happily tell you the legal basis for their entry if you ask them. There may be something in place contractually that your Dad set up with the Feds that your Mom is unaware of. If they can’t answer your question, tell them they need a warrant and contact your congressman same day.
BOOKMARKING
Did she take govt money, now you pay the cost.....................
Tell them via certified mail you expect a complete brief including who will be on your property, the dates, all equipment they’ll be bringing, etc.
Set up game cameras at all access points and post the property immediately. Not sure about your state’s laws, but only a game warden can legally enter posted property in mine without a search warrant. If they just show up, report them as trespassers, contact your Rep and Senators, find an attorney and file suit.
Send them a registered letter, return receipt requested. State in no uncertain terms that no permission is granted. Send a copy to the County Sheriff and other local relevant LE, also by registered mail.
Follow both up with phone calls once delivery is established. Tell them ANY trespassing on your private land will be cause for arrest and that you will file charges.
Do not screw around with these people.
L
Find a way to contact a local militia and set up a roadblock and cordon. It’s HER land, not theirs.
The Bundy's have a TON of data and information for you
Most rural surveys for land use managment, crop surveys, CRP compliance etc. can be done through remote sensing, especially now that LIDAR is available. physical surveys on the property sounds to me like a search for noxious weeds, endangered species, and bodies of water. Danger, Will Robinson. Get a lawyer.