# Killing Bot Fly Eggs on the Horse



## Dreamcatcher Arabians (Nov 14, 2010)

I think the bot fly is the OK state bird. I wait until after the first hard freeze and then I scrape them off with a pumice stone, much faster and easier than a bot knife. I pull the horses out of the pasture on to my asphalt driveway and scrape them there, then wash the driveway down after I've done all of them and put them back out to pasture. 

"The equine botfly presents seasonal difficulties to equestrian caretakers, as it lays eggs on the insides of horses' front legs, on the cannon bone and knees, and sometimes on the throat or nose, depending on the species. These eggs, which look like small, yellow drops of paint, must be carefully removed during the laying season (late summer and early fall) to prevent infestation in the horse. When a horse rubs its nose on its legs, the eggs are transferred to the mouth, and from there to the intestines, where the larvae grow and attach themselves to the stomach lining or the small intestine. The attachment of the larvae to the tissue produces a mild irritation which results in erosions and ulcerations at this site.[8] Removal of the eggs (which adhere to the host's hair) is difficult, since the bone and tendons are directly under the skin on the cannon bones: eggs must be removed with a sharp knife (often a razor blade) or rough sand paper, and caught before they reach the ground. The larvae remain attached and develop for 10–12 months before they are passed out in the feces. Occasionally, horse owners will report seeing the botfly larvae in horse manure. These larvae are cylindrical in shape and are reddish orange in color. In one to two months, adult botflies emerge from the developing larvae and the cycle repeats.[8] Bots can be controlled with several types of dewormers, including dichlorvos, ivermectin, and trichlorfon."

I don't know if anything will kill the eggs while they're on the horse, besides scraping and removal before they hatch. After the first good hard freeze, you can deworm and should take care of the problem. By deworming too often you promote resistance to the dewormers, I wouldn't do it.


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## SueC (Feb 22, 2014)

Hi Pat, thanks for your post!



Dreamcatcher Arabians said:


> I think the bot fly is the OK state bird. I wait until after the first hard freeze and then I scrape them off with a pumice stone, much faster and easier than a bot knife. I pull the horses out of the pasture on to my asphalt driveway and scrape them there, then wash the driveway down after I've done all of them and put them back out to pasture.


I really had to laugh, OK state bird! :clap:
Unfortunately in our climate we can't use the hard freeze so well in controlling the bot cycle. The flies are active in the warmer months from around October to April, and the freezes happen in July/August. We de-worm after the adult flies have cleared off, and again about half a year later, and are sometimes tempted to de-worm mid-fly season because we can get horrendous amounts of larvae in the faeces. In fact, one of our neighbours lost a (de-wormed) horse to a stomach rupture caused by a mass of bot fly larvae... more a problem of sheer masses of eggs for long periods of time, than resistance to the de-wormer... and as you say, you can't really de-worm them monthly...




> I don't know if anything will kill the eggs while they're on the horse, besides scraping and removal before they hatch.


Which only removes them, it doesn't kill them, they're still infectious if picked up by a grazing horse. I get why you use your driveway. We live in a really windy place and I don't know where I could go, other than take my horses completely off the property to scrub the eggs off them, to eliminate the risk of "floating" eggs being picked up by grazing horses...

If any entomologist out there wants to develop an adult botfly trap, I'm buying at least a dozen, sign me up...


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## Saddlebag (Jan 17, 2011)

When the fly lays eggs on the horse's legs, it bites the horse, a nasty bite. Horse grabs at the fly and ingests the eggs. The eggs that you see on the horse can't develop if removed but as long as they remain there a good chance of some being ingested with each bite. Many use a grill stone to remove the eggs as they are sticky. To prevent the flies from biting I use dirty engine oil, good old 10W30. New oil can be used but the dirty is free. It's allowed to sit out for 24 hrs to allow traces of gasoline to dissipate then I wipe it generously on the horse's legs. This does not irritate the horse's skin and it works far better than any spray on the market. Liberally apply every 3 days. It was an old bush worker who used a team to haul logs who told me about this.


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## SueC (Feb 22, 2014)

Hi SB, thanks for your post! 



Saddlebag said:


> When the fly lays eggs on the horse's legs, it bites the horse, a nasty bite. Horse grabs at the fly and ingests the eggs.


Does it really? I've never seen them bite, ours here in Western Australia just seem to hover and lay. The horses avoid swiping at them at all cost, and ingest the eggs later on, accidentally when rubbing their noses and lips against their legs. (Yeuch.) It's the noise of the fly they seem to react to.




> The eggs that you see on the horse can't develop if removed but as long as they remain there a good chance of some being ingested...


As I understand it, development of the bot egg only commences when it is ingested, it's kind of "on pause" until then, for I don't know how long, but if it's anything like other parasite eggs, it could be potentially infectious for many months. I think that's why Pat mentions using the frost to your advantage - frost will definitely kill the eggs. (That's also why putting your pillows in the freezer is such a cool way to kill dust mite!  )

So my concern is that the eggs definitely can develop if ingested from pasture after removal from the horse, just like they can when the horse picks the egg up off its own leg, or another horse's mane.




> Many use a grill stone to remove the eggs as they are sticky. To prevent the flies from biting I use dirty engine oil, good old 10W30. New oil can be used but the dirty is free. It's allowed to sit out for 24 hrs to allow traces of gasoline to dissipate then I wipe it generously on the horse's legs. This does not irritate the horse's skin and it works far better than any spray on the market. Liberally apply every 3 days. It was an old bush worker who used a team to haul logs who told me about this.


I have quite a bit of dirty 10W30 oil saved up, I'm going to give that a shot, thanks, Saddlebag! I take it that it also discourages the flies from laying?


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## Saddlebag (Jan 17, 2011)

The flies will approach to within a few inches but won't land. Just be sure to refresh the oil by the third day. It's almost comical to watch the flies in their confusion as the front legs become part of their reproductive cycle and they can't lay their eggs there.


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## Dreamcatcher Arabians (Nov 14, 2010)

To contain the eggs a little better you can spread a tarp on the ground, stand the horse on it and scrape, then remove the tarp to the trash or burn it, however you dispose of your trash. I use the driveway and wash it down later because the horses never have access to it any other time than when I'm grooming them. 

You won't get rid of them completely, I've never been bot fly FREE even in the deserts of CA and AZ, but you cut way back on them. Do you have fly predators you can buy in Australia? I use them all summer and that seems to really help too.

Personally, I would not use the used motor oil, it's no longer used here in the US because it is a known carcinogen.


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## Shoebox (Apr 18, 2012)

Saddlebag said:


> The flies will approach to within a few inches but won't land. Just be sure to refresh the oil by the third day. It's almost comical to watch the flies in their confusion as the front legs become part of their reproductive cycle and they can't lay their eggs there.


Forgive me if this is a stupid question, but motor oil? Used motor oil contains things that are toxic if ingested (things like polycyclic aromatic hydrocarbons, which causes cancer, heavy metal traces, etc), why would you want to risk that on a horse's legs? That's the same reason you aren't supposed to dump it in the storm sewers and have to dispose of it properly - otherwise it pollutes and toxifies rivers. 

Most horses wouldn't eat that, but some eat all and everything! (Or rub,lip at their legs, etc etc)


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## squirrelfood (Mar 29, 2014)

Yes, kerosene kills the eggs. But you need to be very careful with it. Wipe at them gently with a rag JUST dampened with kerosene. Give it about 10 minutes and wash it off. You still have the eggs, but they are dead and won't hatch. Again, do NOT saturate to the skin. Just surface moisten.


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## SueC (Feb 22, 2014)

Hey, thanks all. Yeah, I know motor oil is toxic, but I'm pretty desperate to avoid getting a stomach rupture on my patch, or ulcers, or internal abscesses, which are worse... My horses don't lick their legs, and they certainly won't if there's something smelly on them, and I'm not sure how much bad stuff can be absorbed through their skin if it's not in a solvent. At ages 29 and 32, my oldies probably won't live long enough to get cancer from it, and are more at risk of the above ailments...

The kero thing I'd heard before...if that works, one could shampoo the horse soon after to remove residue, and then use one of those pumices etc to remove the dead eggs. (But then, although the legs are clean, there is no fly-laying deterrent, which appears to be the motor oil advantage...)

Great idea about the tarp, Pat. On a still day, that might work here. And you can buy fly predators in the US? Tell me more.

Thanks heaps, everyone, for your suggestions.


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## Shoebox (Apr 18, 2012)

SueC said:


> Hey, thanks all. Yeah, I know motor oil is toxic, but I'm pretty desperate to avoid getting a stomach rupture on my patch, or ulcers, or internal abscesses, which are worse... My horses don't lick their legs, and they certainly won't if there's something smelly on them, and I'm not sure how much bad stuff can be absorbed through their skin if it's not in a solvent. At ages 29 and 32, my oldies probably won't live long enough to get cancer from it, and are more at risk of the above ailments...
> 
> The kero thing I'd heard before...if that works, one could shampoo the horse soon after to remove residue, and then use one of those pumices etc to remove the dead eggs. (But then, although the legs are clean, there is no fly-laying deterrent, which appears to be the motor oil advantage...)
> 
> ...


Well your horses' mouth does come into contact with legs, that's why bot flies lay their eggs there - when the horse rubs his face on his leg to scratch, or nips an itch on the leg. So instead of a mouthful of bot eggs, he'll get a nose/mouth/possibly eye full of used motor oil. Bots aren't hard to manage if you routinely worm your horses and rotate wormers - ruptured stomachs and the like really aren't a danger unless you really neglect any worming (never scrape eggs off, never worm). I get bots, and every year I scrape them with a pumice stone during grooming and I worm them every 8 weeks. Fecals done at the end of summer are always clean. And as far as I know, nearly everything will get absorbed into the skin to some degree. The skin is very porous. Here's a CDC article about it. Mechanics is one occupation that's listed as "at risk" for dangerous chemicals being absorbed through skin.

http://www.cdc.gov/niosh/topics/skin/

It's up to you - do what you will, just be smart about it and do some good research first. a 90 year old woman could pick up smoking and she would likely not live long enough for it to give her cancer, but it doesn't make it good for her! :wink:


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## squirrelfood (Mar 29, 2014)

Simple vaseline wiped over the hair is a fair deterrent, but it attracts a lot of dirt.


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## Dreamcatcher Arabians (Nov 14, 2010)

Fly Eliminators from ARBICO - Biological Fly Control for Horses and Livestock

Here's where I get mine, they have all kinds of neat stuff. I never believed in the fly predators until I lived less than a mile from Arbico and discovered.....no flies at a boarding facility. That made a believer of me and I've used their products ever since. 

EM-1 Microbial Inoculant 12 oz - Concentrated Soil Conditioner

This product is phenomenal for breaking down the waste products, either in your manure pile or out on pasture.


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## SueC (Feb 22, 2014)

Shoebox said:


> Bots aren't hard to manage if you routinely worm your horses and rotate wormers - ruptured stomachs and the like really aren't a danger unless you really neglect any worming (never scrape eggs off, never worm).


SB, have you read my original post? Around here, bots are hard to manage because there is such an infestation due to being surrounded by non-worming horse owners that you would have to worm monthly during the 6-month bot season to be in the clear, and you can't do that because of resistance issues, expense, and because even wormers aren't great chemicals for horses to be over-exposed to. 




> It's up to you - do what you will, just be smart about it and do some good research first. a 90 year old woman could pick up smoking and she would likely not live long enough for it to give her cancer, but it doesn't make it good for her! :wink:


The external application of motor oil to skin is not comparable in potential damage to the daily inhalation of carcinogenic and toxic substances into the respiratory membranes, or the ingestion of such substances. That's why LD-50 testing distinguishes between absorption through skin, lungs, and gut. Also, I should think that applying motor oil is actually safer than commercially available personal insect repellents, which contain far nastier substances, and solvents to carry them into the bloodstream to boot.

This is why, although not ideal, the ideas of some of the other posters about motor oil and kerosene deserve consideration, when compared with the far more dangerous alternatives of internal damage caused by bot larvae.

Thank you for being part of the discussion, I appreciate it.


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## Saddlebag (Jan 17, 2011)

Engine oil was toxic for about 10 years with all the additives but too many complaints about engines not running properly on it. I've never seen a mechanic develop skin problems and their hands are in oil all the time. If you don't want to use engine oil then chain saw oil will work. It's mainly sugar yet doesn't attract flies. Horses will have red legs.


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## SueC (Feb 22, 2014)

Something else I just wanted to throw into the mix: Here is south-western Australia, which has a Mediterranean climate (dry summers, wet winters), dung beetles were introduced from other countries to deal with the large manure piles from the imported farm animals (cows and horses especially). Native grazing herbivores generally have a small pelleted manure, not the great plops of our domesticated stock, whose manure piles created breeding grounds for flies. (You know the "friendly Aussie wave"? ;-) ) The dung beetles act as a biological control to reduce fly breeding.

The wormers which kill bots also kill the dung beetles who land on the manure of a wormed horse, so frequent worming of a horse during the summer, which is undesirable for other reasons discussed previously, would also pretty much wipe out the dung beetle population and cause nuisance flies, not just the bush flies that crawl around eyes and noses, but small biting flies as well, the combination of which can really plague horses and cattle!

We worm towards the start and at the end of the bot (and dung beetle) season. I'm really looking for other ways to break the bot cycle in-between worming, because otherwise the larvae will build up to unacceptable levels. I knew about some people using kero, I knew about the bot knife, but this is a large international forum, so it's great for getting out-of-the-box suggestions, and learning other ways of doing things. That's why I put the question out there, and thank you all for your suggestions so far!


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## SueC (Feb 22, 2014)

Dreamcatcher Arabians said:


> Fly Eliminators from ARBICO - Biological Fly Control for Horses and Livestock
> 
> Here's where I get mine, they have all kinds of neat stuff. I never believed in the fly predators until I lived less than a mile from Arbico and discovered.....no flies at a boarding facility. That made a believer of me and I've used their products ever since.
> 
> ...


Pat, that is so cool! Thanks for that information. We presently use fly traps for stable and bush flies, which help reduce those populations, and we have dung beetles (see above post). It would be great if someone invented a trap for adult bot flies, like they have for fruit flies and other nuisance flies, and moths, and cockroaches...


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## squirrelfood (Mar 29, 2014)

USED motor oil carries enough metal fines to be something I don't want on my horse.


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## Dreamcatcher Arabians (Nov 14, 2010)

SueC said:


> Pat, that is so cool! Thanks for that information. We presently use fly traps for stable and bush flies, which help reduce those populations, and we have dung beetles (see above post). It would be great if someone invented a trap for adult bot flies, like they have for fruit flies and other nuisance flies, and moths, and cockroaches...


Did you look through their whole site? They have various fly traps and all kinds of neat things for the organically inclined. I loved living down the street from them (ok maybe not so much down wind on those occasions) and learned quite a bit from my visits to buy my fly predators.


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## SueC (Feb 22, 2014)

Yes, Pat, fascinating reading.  We have fly traps like that here that smell to high heaven but are non-toxic and can be emptied into the compost. I think their microbial stuff and biological control organisms is most interesting. We can't import any of the latter into Australia because it's a different ecosystem to yours (and just look at what happened here with cane toads, our famous biological control of sugar cane beetles gone wrong!), but I can start poking around Australian sites to see if anything that suits our conditions and biota is available here.

This is why it's so great to talk to people from everywhere on this planet! Digs up interesting stuff.

Saddlebag, my motor oil must be different to yours, or maybe we have less choosy bots, I tried it out on a horse and the next day there was a botfly laying on the leg, don't ask me how. I am now thinking of trying peppermint oil - but that has the complication of stinging the horse's eye if it makes contact.

Another person said to me today that kerosene actually bursts and kills bot eggs, so I'll do some more investigations there.

Otherwise, it might be back to the bot knife and that tarp Pat suggested, on a still day...

I'd like to do anything I can on top of worming, to get rid of these creatures...:twisted:


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## Dreamcatcher Arabians (Nov 14, 2010)

Have you tried a pumice stone instead of the bot knife? I don't even own a bot knife anymore, the pumice is so much easier.


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## amigoboy (Feb 14, 2014)

hi SueC.
Oh No, man that really sucks!! This is exactly what is happening over here, people here have got the "RESISTANCE PARANOIA" so they don´t deworm their horses.
People have no common sense at all.

The Bot Fly can fly several km. looking for a host, it´s a real bummer when neighboring ranches don´t treat their stock.
Egg. You have too scrape them off and they are pretty tuff, often times what you see are the yellow shell, the larv has already burroed into the horse or has been injested by licking.
DO NOT USE CEMECLES, KEROSEN, ENGIN OIL AND SUCH!! there is the risk they will get it in their eyes or lick the stuff.
You have to break the Life Cycle, here in Sweden we deworm the horses around Nov. - Jan. as this is the best time to get rid of most of them treating them with a Ivermactin desighn to take bots. (most Iver takes bot I think).
The Bot Fly can swarm into the beginning of fall Sept. The eggs have a incubation time of around 6 weeks inside the horses mouth, then they work their way into the stomach lining where they feed causeing sores and taking nuritionment fromt the horse. The horse can die from over infestation.
We want the give the larv time too develope to the treatment will be most effective.
Equimax Aus. had a very good youtube worm series but I can not find it.
check out Equimax
Amigo


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## amigoboy (Feb 14, 2014)

YAHOOOO SueC.......I found it!!




A series of 12.
For you on Bots.




Very good information.
I think they are Aussi films.


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## SueC (Feb 22, 2014)

Thanks for the clips, Amigo!  Our horses get IMAX Gold three months apart during the bot season, our vet says resistance becomes a problem when people routinely use it every 6 weeks. And as you say, the ******s start burrowing into the horses again in weeks. My vet was over today to do teeth. I quizzed him on the posted question and he said one way to kill the eggs was to sponge the legs with very warm water. He says this simulates the licking and starts the hatching phase. Then you scrape them off and let them fall on dry ground / a place where the horses don't eat, where they will quickly perish. Without the warm water treatment they stay in their little safety capsules and remain viable for a while. He's sceptical about kerosene killing the eggs.

I still think the perfect complement to worming for bots would be an adult fly attracting trap... when / if that gets invented, I'm buying!


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## amigoboy (Feb 14, 2014)

SueC said:


> Thanks for the clips, Amigo!  Our horses get IMAX Gold three months apart during the bot season, our vet says resistance becomes a problem when people routinely use it every 6 weeks. And as you say, the ******s start burrowing into the horses again in weeks. My vet was over today to do teeth. I quizzed him on the posted question and he said one way to kill the eggs was to sponge the legs with very warm water. * He says this simulates the licking and starts the hatching phase*. Then you scrape them off and let them fall on dry ground / a place where the horses don't eat, where they will quickly perish. Without the warm water treatment they stay in their little safety capsules and remain viable for a while. He's sceptical about kerosene killing the eggs.
> 
> I still think the perfect complement to worming for bots would be an adult fly attracting trap... when / if that gets invented, I'm buying!


Big fights back and forth on this resistance buisness It all started here with the Islandic Pony People, a tight group that got into the over treating their horses, every month they´d trott down to the drug store and buy dewormers useing the same typ time after time, for all their knowlage they knew nothing about rotating. To make matters worse they under dosed the horses so the wormer was not haveing the desired effect, instead to breaking the life cycle they were makeing the worms resistance, so red flags went up all over the place and the goverment declared worm meds as a Controled Substance that only the vet can write out with the recomendation that egg counts be made before the vet write out the meds. The result being many horses are not being dewormed for long periods, I know some that have not been dewormed in several years because the test shows 0 - low infestation. The older experiance horse vets do not rely on the test but will write out the medicine if asked. 

You lost me?? you mean the horse starts to lick?
NOw that´s an idea, sticky fly paper that attracts bot flys.


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## SueC (Feb 22, 2014)

I was thinking of a trap, like a bottle trap, with irresistible pheromones like they do for fruit flies. Just don't have the pheromones. Of course, I expect that once they're ready to lay, they mightn't be so interested in pheromones anymore...

Well, Colin's theory is that the warm water replicates the contact with inside the horse's mouth when they scratch themselves and somehow get the eggs in their mouths, and therefore set off the hatching phase. The horses don't lick per se. Sorry late night, not communicating clearly, sick old mare. :-(

Hey Pat, yes, a pumice sounds easier, I'll try it!


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## amigoboy (Feb 14, 2014)

Oh, I see.
From what I´v read the eggs hatch and the larv will irritate the skin causing the horse to bite and lick itself.
The bot fly lays eggs around the horses mouth as well. I think they mention that in the films I sent you.
Do you have bots year around?


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## SueC (Feb 22, 2014)

See Post 1!


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## SueC (Feb 22, 2014)

...actually, it's Post 3. Oops. ;-)


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## jaydee (May 10, 2012)

You could invest in some leg protectors that keep the flies off the legs - made from the same stuff as fly sheets. They do mostly lay the eggs on their legs
A bit of baby oil or Vaseline wiped over the legs seems seems to help stop the eggs from clinging to the hair and clumps them together on the blade when you scrape them off so you can just wipe them onto a piece of cloth or kitchen roll


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## Corporal (Jul 29, 2010)

I like the driveway idea. Also, you could mix bleach 1/2 and 1/2 with water, and drip the eggs in that. Pretty much the pumice stone or the bot fly comb and elbow grease, and you'll get a handle on this. =D
I would suggest that you get your Vet to do fecal counts on all of your horses so that you know who is liable to pick up all of the OTHER parasites that are living there.


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## SueC (Feb 22, 2014)

Our property never had horses on it before and the horses were clean when they came. The eggs counts (not bots) we did all our lives before that always came up negligible (for _all_ the horses on my family of origin's property). We still worm, as discussed before.


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## amigoboy (Feb 14, 2014)

jaydee said:


> You could invest in some leg protectors that keep the flies off the legs - made from the same stuff as fly sheets. They do mostly lay the eggs on their legs
> A bit of baby oil or Vaseline wiped over the legs seems seems to help stop the eggs from clinging to the hair and clumps them together on the blade when you scrape them off so you can just wipe them onto a piece of cloth or kitchen roll


Can minimize but will not stop it as they lay eggs around the mouth and as Sue said in the mane and withers, anywhere they can. Horses love scratching each other for social bonding, they get it that way.
Vaseline and oil is just going to make a sticky dirty mess....yuck.


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## jaydee (May 10, 2012)

I would do anything to minimize it - mess or otherwise and Baby Oil isn't messy, I often wipe my horses over with it because it seems to deter the ticks as well
Worming to kill any larvae will help reduce the flies but if the neighbours don't do their stock its just going to be a drop in the ocean - though of course it still should be done
They also infest other animals that she has no control of
Stabling the horses during the time of day when they're most active could be the easiest solution because they never seem to fly into the barn


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