I've looked through all the books I have on the setting, checked the Pathfinder Wiki, and Googled... but I can't find what descriptor is used for the folk of Erastil. Are they Erastilites? Erastilians? Erastilese? Anyone know?
We use "Erastilians" ourselves, though that's hardly canon. We may have seen it somewhere (in the Kingmaker AP), but I'm really not sure.
Farmers.
Heh. True. True.
(Among others.)
I would go with Erastilites, or perhaps just Erastites. -ite seems to be the common 'follower of' suffix from what I can determine.