Giant horse flies

Any updates on giant horse fly control? My horses are being eaten alive by flies the size of vultures. I can’t use fly sheets because it’s too hot this time of year. I tried those black balls with sticky goo and I tried a homemade fly cage last year, but the only flies I caught bumbled in there by accident. I catch more in my tack room window. Anything new on the market? I want a dome for my farm, complete with rain on demand.

Hope this hasn’t come up too recently, I’m hardly on COTH since the forum interface change. I tried to search but “giant horse flies” returns a surprising variety of topics, few of which have anything to do with this menace.


Can you get CLAC/Deo Gel? I’m noticing if I reapply it daily down their topline, the very big bugs don’t land on them. It only works directly where it is applied though, it doesn’t have a “radius” the way some fly sprays do.

You could feed oats or get a bird feeder. The presence of birds deters big flies. We have a huge roost of song sparrows that occupy the run-in sheds; while at first the amount of poo on everything was annoying, they do WORK on the bugs. Just make sure if you get a bird feeder, you don’t flyspray near it.

BTW, welcome back! It’s been a minute.



I have bird feeders at the house and a neighborhood of barn swallow families in the barn, but I could definitely do more to attract them out to the pastures. That hadn’t occurred to me before. Do you mean feed oats to the horses because the birds will eat the seeds from the manure?

I had not heard of CLAC/deo before. Unfortunately I have one horse who is massively allergic to essential oils like lavender and clove. His skin erupts and peels off into raw pusfilled sores, barf. I try not to have any of that type of thing in the barn so he doesn’t get accidentally touched by it. I can use swat on him, maybe I’ll try a thick line of that down the top line. It’s the giant spine sucking flies that are the worst, they can protect their shoulders and sides pretty well with their own tails and nose.

1 Like

Keep the horses in when the flies are at their worst and turn out overnight?


Yeah, horses are in during the heat of the day. Around here the flies are bad from dawn
to dusk. Anyway, I’m looking more for fly eradicating tools and products, and especially wondering if anything new has hit the market in the last decade or so.

Some people seem to find ecovet effective for the big horse flies. I’ve not had the same luck, but it’s worth a shot!

The hot & dry weather seems to have kicked up the population here, I’ve never seen so many as this year.

Nothing new here… the Horse Pal traps work. You might have to experiment with placement. Those flies are sight hunters, they go after dark moving objects. If a bite is unsuccessful, they fly upwards.

Every female in the jar is one who is not breeding more!


Fans. They aren’t strong fliers, so the more air movement the better. I’ve found no fly spray works for them. They are sight feeders, not smell or CO2 feeders like stable flies and mosquitoes are, so they aren’t as effected/confused by fly spray.

However you can do some preventative measures. They start their life cycle in water. Using BTi spray or granules in water sources on your property may prevent them from being able to complete their lifecycle. It also stops regular fly and mosquito larvae too.

1 Like

Oh! I didn’t know that. I’ve been using Bti dunks this year for the first time and have seen a vast mosquito improvement, though maybe that’s also due to our stinkin’ droughty July. Do you know how long it takes to be effective? Are this year’s flies last year’s eggs?
I do have a creek at the back of the property that I obviously can’t treat with BTI, but I’ve been putting the dunks in all the waterers and even crumbles in the wash stall’s little puddle.

I tried a homemade horsepal that my husband made for me and moved it around but never could find a sweet spot. Caught some greenheads, but not even the slightest dent in the population and none of the giant black horseflies. It blew over in the wind a lot, which maybe the real Horsepal would be better anchored. I guess I’m just really hesitant to spend $300 on something I’m not sure will work. :grimacing:

I tried ecovet one time and it attracted a ton of Japanese beetles! It was crazy, they were flying in and trying to land on the horses I had sprayed and the horses were a bit freaked. Weirdest thing I’d ever seen with a fly spray. Tried it a couple times and then threw it away. The smell was also breath taking, in a bad way. That was when it was new on the market, I think maybe they’ve changed the formula.


No, it will still make you choke and your eyes water.:woman_facepalming:

1 Like

Ah, too bad, it was not a very comfortable feeling!

1 Like

Yeah it’s still pretty terrible! It’s less awful cut with another spray. I’ve never found it very impressive, but some people rave about it. Every couple years I get suckered into trying it again :rofl:

1 Like

Usually it takes about 3 weeks to start seeing results. Basically, you have to wait for the adults to die off. The BTi works on larvae, so even if the eggs overwinter when they hatch they will be affected and not mature to adulthood.

From what I know about horse/deer flies, most species have an aquatic larvae stage. This means the BTi will kill them. However, some species can have their larvae on land. They tend to lay their eggs/larvae in thick, tall foliage (grass) so if you can mow your property short that should help quite a big. I’m not an entomologist so maybe someone with more experience in this can explain which species and what locations need to be doing that.

The Horse Pal fly trap works. I have one for the first time this year and it has caught so many horse and deer flies, as well as the occasional wasp or green head.

1 Like

I have two of those and one big H-trap. ALLLLLLL empty. I have one of the Pal’s hanging from a pecan branch and my hay feeder right underneath. The horses will stand right under the ball, i mean the ball is TOUCHING whoever is there, and horseflies will go to the horse’s back (light colored horses both of them) and never hit on the black ball and fly up into the trap. It is empty. Never has caught even one.
Nor has the other one at the other barn.

Only thing that gives my horses relief it their barns. They have 24/7 run-in barns and have pretty much become nocturnal.

About this time of the year, every year, i have become pretty sick and tired of parasites.


That’s so weird. I will say that we moved my fly trap around a good bit before we found the spots that really caught the bugs. Some spots just didn’t work well and others produced tons of fly carcasses. It was just trial and error.

What I find interesting about the giant horse flies is how few of them there are these past many years. In an old journal I’d written one day that I killed 30 - yes 30 - with a broom on a wall. That was 25 yrs ago.

Anyone notice that big change? And so thankful for it. They are as evil as wasps.

1 Like

I started using Ecovet fly spray and that has been a godsend. It smell awful and you have to spray it in a ventilated area but you only spray legs croup and neck and nothing touches them.

1 Like