I just placed my first order today. You can have them bill with each shipment if you don't want to pay the whole year at once (well, at least with Arbico), you just note it in the comment field at checkout. You're supposed to release them every 3-4 weeks due to their and the flies' life cycle. I opted for the every 3 weeks because we already have a lot of flies... we get them bad. So, hoping it works as well as I hear it does!
Folks, how do you use them? I heard you suppose to put them on manure around the barn, but we clean everything around the barn twice a day so essentially there are not so many piles around anyway. Is it still worse it?
I don't place them on the poo piles just near the poo "hot spots" or places the horses like to do their thing. Our girls have certain areas they use more than others so that's where I put the fly predators. I also put some near my large manure pile.
I like to put them in as much of a protected area as I can since birds like to eat them. I sprinkle along and behind the fence line, next to fence posts etc. I think they recommend every 30 feet or so. They come in a sealed bag with some wood chips mixed in. As soon as I see a few of them starting to hatch and crawl around in the bag I go sprinkle them. (don't wait until you have hundreds crawling around just look for about 10-15 bugs) If you already have flys when you release its best to set out some fly traps as well. I do both all summer and we have very few flys considering we have 6 dogs and chickens that all draw flys.
ETA Kitten, when you order they ask what your horsekeeping is like. If you remove manure daily weekly etc, if you store the manure or haul it off. All those things will guide you on how many fly predators you should order. Hope that helps