I have had dogs as pets for more than 50 years and they are inside pets, but are let out to a fenced area constantly during all year and I have found that at spring before the first mowing. I will go to Walmart and get 2 large 0.5 cubic ft bags of cedar chips or bedding and sprinkle it throughout the areas where the dogs will be. I do this before the first mowing and after I mow the yard it will scatter the chips even better and finer.
I never have fleas and to check occasionly, I will fill small bowls with water and a few drops of dishsoap , place them under a wall outlet with a nightlight on overnite and in the morning if there were any fleas in the house, they will be dead and in the bowls. I always do this ritual every year faithfully and never have a flea problem in my yard.