Stay home for 14 days from the time you left an area with widespread, ongoing community spread (Level 3 Travel Health Notice countries) and practice social distancing.
Take these steps to monitor your health and practice social distancing:
Take your temperature with a thermometer two times a day and monitor for fever. Also watch for cough or trouble breathing.
Stay home and avoid contact with others. Do not go to work or school for this 14-day period. Discuss your work situation with your employer before returning to work.
Do not take public transportation, taxis, or ride-shares during the time you are practicing social distancing.
Avoid crowded places (such as shopping centers and movie theaters) and limit your activities in public.
Keep your distance from others (about 6 feet or 2 meters).
The CDC guidelines read to me like your friend and his wife can work by themselves on their farm as long as they practice social distancing.