looking at fly sprays. i have been using Ultrashield for many years. it seems to have the highest concentration of Permethrin of any of the fly sprays. But is that what keeps flies away? Or does it just kill them/make them ill when they bite the horse?
Is Deet dangerous on the horse? I really want to keep my horses as fly free as possible, but i'd like to know the general opinion on this.
Flies have VERY high tolerance to permethrin due to massive use and overuse over the years. You might get some knock down of the flies initially, but they will get back up and be all over your horse as soon as you turn your back. You are actually aiding the resistance problem by using it.
The other issue is that it is really tough to get any sort of control product to stick to a horse for any length of time. Horses sweat really well and between that and rolling in the dirt it is off before you can say "boo"
Your best bet is to set up some sort of IPM system including increased cultural control and sanitation, trapping for the type of fly you have, the use of biological control agents, personal protection like fly masks, blankets and leg wraps and if you have an outbreak after all that, spot treatment of pyrethroid based products.
When shopping for pyrethroid insecticides such as permethrin, also look for Piperonyl butoxide as an ingredient. It is a synergist that helps them work better.
Also, if mixing your own, the use of alkaline water ( above pH 7) or addition of anything alkaline will cause it to degrade quickly. A small splash if vinegar could be helpful if you are forced to use alkaline water to mix.
Please be very sparing with your use of permethrin, especially if you live near any bodies of water. It is extremely toxic to fish. When I worked in an aquatic toxicology lab, pyrethroids were the number one problem. They are also toxic to beneficial insects like bees.
As Peter, Paul, and Mary say, a dragon lives forever.
Some horses are allergic to Permethrins. We have one who cannot tolerate it.......he breaks out in hives whereever you spray him. For years we thought it was the fly bites but finally figured out it was the fly spray. We only use sprays with pyrethrins or other natural ingredients now.