The Farmers Market Coalition (FMC) has published a resource for farmers market managers, vendors, and other members of the local food system with information regarding COVID19. This resource includes preventative measures, market operations procedures, and other information that will help keep your community and market safe during this time.
Key points include providing preventative sanitation methods at your market (such as handwashing stations and tissues), limiting cooking demonstrations and samples to avoid opportunities for cross contamination, and providing sanitary gloves for staff members who handle things like money and payment vouchers.
Find these resources and more on the FMC website here.
Additionally, the State of Michigan and Michigan Department of Health and Human Services have created resources that include COVID19 facts, preventative measures, and recommendations. Those are available here and here.