I am currently training an unbroke, 5 or 6 year old Mustang gelding for a lady to gain experience.  Let's just say that he was the most disrespectful, pushy, rank horse I've ever worked with.  I was sore for several days from whacking his rump and shoulders with my stick.  But he's finally become respectful, listening, and decent--not as good as he will become in a couple of weeks, but good enough.

However, we ran into problems with the plastic bag.  I won't get on a horse unless he's respectful and is not afraid of the plastic bag, and so far by using this method (Clinton Anderson's methods) I have not had a horse buck when I first get on them (knock on wood, LOL).  But this horse is very difficult.  The first time I brought the bag out, he reared, struck out at it, tried to jump on top of me, bucked like a rodeo bronc when it got near his back, and kicked out at me.  I worked him several days in a row and was having difficulty getting him to accept it, but I finally got him to accept it flapping all around him and all over his body, on both sides, and on his face, even while he was walking in a circle (purposely "desensitizing in motion").

But the problem is, every time I bring this horse out again to work with him, he acts like he's never seen the bag before.  He kicks at me, snorts, strikes, etc. for fifteen to twenty minutes before I can finally get him back to where I had him the day before.  I just don't understand it--I've done everything.  I stand there and flap that bag until he's bored to death, so I don't believe I'm taking away the pressure too early.  He's a little tricky, because even after the standard fifteen seconds (if they haven't shown a sign of relaxing) he'll often still be tense and nervous.  But I keep flapping past that until his muscles relax, his head drops a little and his eyes soften.  I've tried running at this horse with the plastic bag, flapping it under his belly (though never to the other side!), sneaking around him to try and get him to react so I can fix it.  For some reason his problem is more when I sneak around him then when I become obvious, so I've done lots of it to get him used to it.  Yet still he flips out at the beginning of each session.  I even tie him for an hour or two after the session to help him think about it.  Is there anything I could be doing wrong to cause this?  Or are there just some horses out there that never truly get used to a plastic bag?  I don't feel confident enough to ride this horse until I get him over this fear, and during that time his owner is paying to feed him without getting the entire point of bringing him over--breaking him and riding him--accomplished.

Is this horse a recent capture or has he been in captivity for a while? And how long have you been working with him so far?

He was a wild stallion until about three years of age, then was caught, gelded, and has been in the lady's care for about two or three years (she has so many horses she forgot how old he is).  He's completely gentle to touch, etc.  The strange thing is that he's fine with the rope being thrown over his back, the stick and string slapping the ground and whirling above his head, and yet he still flips out when he sees a plastic bag.  He's also extremely lazy and on the generally bored, quiet side.  But I might take your advice and leave the plastic bag problem for awhile, and come back to it later on in his training.  That's probably part of my problem: I've been working on it for about a week's worth of days now (spread out into about ten days) and he's probably gotten into the habit of being scared every day.  Maybe if he comes to respect and trust me more, he'll come to accept the plastic bag.

Have you considered using a cloth flag istead of plastic bag? You could start with the cloth then transition to bag - I get my horses off the range in MT and find that non-rattlesnake-sounding things are better. 

What I have had success with is reducing the size of the area that the horse is in - We have permanently welded 12' x 12' 6 1/2' tall pens - The horse is free inside and the handler is outside. Our horses stand in those pens for a couple of hours every day - if not all day. It's good for a horse's brain to stand contained or tied for a length of time. So after the horse is relaxed standing on his own, I start the desensitization. 

I start far enough away that the horse doesn't react to the bag (I don't want them to even look at me - I want to elicit no response). I wave it and make a lot of commotion away from the horse. I stop BEFORE the horse reacts and leave completely. If the horse does respond, it's a learned fear - much harder to deal with - but the next steps are still the same.

I leave the horse standing quietly. I go do something else then come back and do the same thing, this time I take a step forward so that I'm closer. I want to see a widening of the eye, a snort, etc - I don't want the horse to actually start moving in fear, but I do want the horse to show some of his natural instinct - I maintain that distance and let the horse sort it out. I don't stop after 15 seconds - sometimes I'll be waving a flag around a horse, pushing them, for minutes at a time. I look for the slightest relaxation at first, a tipped ear, lowered head, relaxed tail, a breath. As soon as there is a change - I stop and I give the horse a break from the scariness for an equal amount of time as it took to get that change. I'll stay at this stage for several sessios - the longer you stay here, the more likely you'll be successful. 

After the horse has learned that the bag is not scary from a distance, I will approach the pen and increase the pressure. The horse will move their feet, they will kick, snort, buck, rear, try to climb out - or if you did a really good job and the horse was super comfortable with the previous step, the horse will pace around, face you, and then you'll stop and let the horse relax. Again the rule is the horse gets to rest for as long as you had to work to get a change.

The goal is to get to the point where you're sitting on the fence, waving the bag and the horse is unconcerned.

After the horse accepts the bag from the fence, you get into the pen with the horse. The horse will have a halter on at this point so that you can tur their haunches away from you. You have a contained area that will prevent too much speed - but watch yourself, this is a place that can be very dangerous for a person who is not 100% aware of their and their horse's movements.

You then introduce the bag as an aid - it means something, You use it to move the haunches and shoulders. In fact if I really hit a brick wall trying to get a horse to accept the scary thing, I just start using it as an aid much sooner and alot of times the horse will accept the bag because it's not just a scary thing, but a tool with a purpose.

I have a mare that had similar problems with trailers, she reacted slightly less violently than what you describe.  Finally my dad (a cattle person) decided that he was sick of the trailer taking up space in the driveway and the horse's response so he just parked it in her turnout.  Since she lives in a runin shed she was stuck with the trailer.  It took about a month but she finally stopped having a meltdown at the sight of the trailer.  After which we hooked it up to an old tractor and put blocks under the back as well as behind all the tires and we rigged the door (stock trailer) so it would stay open.  we started feeding her near the trailer and slowly moving the food closer until she had to climb into the trailer to eat.  Once she was accustomed to that we started closing her in until she settled and then letting her out.  We finally got her so she would go into the trailer, granted she's still the worst horse I've ever trailered (we have to leave her loose in a space about the size of a box stall, little smaller) and whenever we stop she starts spinning.

My other horse used to be scared of plastic bags as well so I tried the same method of leaving the things around his pen, especially where they could flap in the wind, he still doesn't like them, but he tolerates them.

This is VERY common in Mustangs for good reason.  A mustang’s first interaction with humans is with the BLM wranglers.  Out of necessity and convenience the wranglers use sticks with plastic bags to separate, herd, or stop the horses from running them over.  Nearly all Mustangs come with a caution of bags pre-installed for you.  Most get over this pretty quickly but others take a very long time, and we even had one that just never got over it 100%.  It wasn’t a spookiness to other things, only bags.  It is because they’re first association with them was one of fear.  It’s a bummer but those of us who train a lot of Mustangs know that the wranglers don’t have much of a choice.  They have to get the job done and take care of thousands of unwanted Mustangs the best they can.  

Great forum post.

Kudos to FloridaHorseman, Katie, Lovmyhorses and madel_equiestrians for excellent feedback. I was going to give my $0.02 worth, but after reading your posts, I'm sure that reining_lover has great advice to go with.

Thanks for participating in this forum!

Mark Seller
http://equimed.com

 What others said - training takes as long as it takes. A horse is a horse.

I desensitized a mare that hated plastic bags by putting treats in them. Gave her the treat by hand or in a bucket first, then in the bag. You could put the bag flat on the ground with the item in it or in a bucket with the treat inside, not in your hand so it is not associated with a human (wrangler).  Of course with a mustang, this might not work but it didn't take long for my mare to look forward to seeing a plastic bag, even out on trails flying beneath her legs.