Hi Jayne! 

A few short-term options to control smaller populations of prairie dogs include baiting, relocating or shooting the prairie dogs. A little more information about this can be found in this factsheet: https://extension.colostate.edu/topic-areas/natural-resources/managing-prairie-dogs-6-506/

This booklet also has good instruction about installing visual barriers, monitoring and closing prairie dog tunnels as non-lethal management methods: https://habitatharmony.org/docs/hpdm-6x9-web-v2.pdf

Preventing future infestations will require you to keep montioring and managing the pasture to discourage future colonies to move in. Visual barriers are a great way to dicourage prairie dogs from moving into an area. Prairie dogs like having a full view of their surroundings so if you have a permitere fence you can block the lower portion of it with a silt fence, vinyl or other light blocking materials and skirt it with chicken wire that extends to the side were the prairie dogs are moving form. On the long term, you might need to encourage natural visual barriers like planting thick brushes and trees surrounding the property. 

Junipers, wild rose, rabbitbrush and other low-growing bushes are great at deterring prairie dogs from the property. Short vegetation and grasses make for great prairie dog habitats so you want to encourage grass and plant growth if possible. 

Thanks for reaching out!

-Karla