They are actually tiny, stingless wasps that feed on the larvae of flies.  I've seen them advertised in some catalogs, possibly Valley Vet or American Livestock.  You can do a search on line to find out more and where to purchase.  I have never used them, flie strips do the job for my barn, but I have heard that people like them.  I don't believe they are cheap though and they have to be replenished after a while.  I also don't think they eat greenies or deer flies, more for regular stable flies.

I found this site that tells you about them.  Just put your cursor on it and click.

Biological Control of Flies

And I jusst saw this site posted on another forum!  They sell the predators.  Fly Parasites from ARBICO - Biological Fly Control for Horses and Livestock

I use the fly predators from Spalding Labs. It is best to start them in the spring - just before fly season starts. I get the smallest amount it is $19 each month. These predators do not EAT the flies, they eat the larvae of the fly. So - you may still have flies, but you can severely reduce the next generations of flies. I also use fly traps... but do NOT place them IN the barn because you will only be drawing the flies to the barn...

Last year was my first year using them and I think it has made a TREMENDOUS difference in the how few I have this year. I do have a large mosquito population (I use the donut shaped dunks in any standing water on my property but there are ponds within a 1/2 mile of my property) this year and the deer flies have been extra wicked, but very few regular flies... I got a late start this year since we had snow in May....

For trail riding, I always use DEET repellant wipes, down the neck of the horse, across his rump, his belly (where there is no girth) and on his lower legs to kill any possible ticks.  I would not use DEET on a daily basis for pasture though. I use Tri-Tech 14 for pasture / hanging out repellant and insecticide.

With the fly predators - you have to be careful in using sprays...otherwise you will kill the predators. Also - if you have neighbors that do not do anything for fly control - it would be a waste of money.

I've used the fly predators from Spalding Labs for about 4 years now. They really cut down on the fly population. You need to start them early in the Spring (to get the first flies before they get a chance to multiply!) and continue through fly season. They work best if any neighbors who have livestock use them too, but my neighbors don't use them. I guess they'd work even better if the neighbors participated.

One thing I saw in the feed store yesterday was fly strips you attach to your horse. They had ones you put around the neck, the pasterns and the tail. I think they said they work on deer flies, mosquitos, and ticks too. Anyone tried them? Which brand(s) work?

I live in Middle Tennessee.  The deer flies are worse this year but still not as bad as what some of you are having to live thru

We are inundated with ticks, however.  I started my horses on equine garlic last March and it is still working to 90% effectivity on all four horses.

I am only feeding each horse 1 teaspoon 2X/day, which is way below the recommendation, because I worry about anemia if they eat too much garlic.

It's doing an ok job keeping some types of flies away too.  However, the house flies and those knat flies seem to be able to work right past the garlic odor.

I work part time and won't leave my horses locked up while I'm gone, so I STILL spray them before morning turnout.

I have gone back to mixing Repel-X for the rest of the summer because it and "Endure" seem to be the only two sprays that are effective at this point of the fly season.  I need another job to pay for fly spray-lol

For trail riding, I HIGHLY recommend masks with ears.

Also, a lady on another message board posted a picture of her  horse's new "complete body fly suit".  I can see the advantages to that for a lot of you folks that are much worse off than I am in the fly department.

Here is the web site for the equine garlic if anyone is interested.

http://www.herbs4horses.com/

In closing, I need to comment that I will be taking the horses off garlic around October/November and will start them back up next March.  This will give their systems time to cleanse from the garlic.

Hope this helps some

Judy

Got a couple of neckbands which contain citronella.  They were ok but our horses could only wear them 2 or 3 days at a time.  They attach with velcro so they were safe but they made our horses skin flake if left on too long.

Now using the crochet ear nets to which we have sewn on a piece of netting to cover the neck, and tie it underneath.

Have had good results with using 1 part pinesol to 4 parts water as a spray.

Maybe we'll get an early frost.

I've tried the fly strips that have snaps on them and you attach them around the horse's pasterns and neck.  They smelled like citronella but I dont think they did much good because the flies would even land on them.  I dont remember what brand they were though. 

I've also used the tea tree oil, but that was for fungus, it didnt seem to have any effect on the flies.

Spaldinglabs.com

They sell "Fly Predators".  They work great

Nancy

We are also using fly predators for the first time this year.  I think they are helping.  Our farrier said we'll see a huge difference the second year.  I'm paying $18 per month for predators and have 5 horses.

For a wipe on trail riding, I mix Skin-so-soft too, with vinegar, a fly repellant concentrate and water.  I sponge it using a stripe down the back, under the belly and down each leg.  On faces I use Swat.

After a long hot ride, I'll put a little of my mix in the water I sponge the horse down with, it really helps. 

At home along with the predators I use the disposable fly attractent bags. 

The Great Bug Battle!