Surprisingly, not just worms and caterpillars! The common application (sold as thuricide) contains var kurstaki, which is selective for lepidopterans like worms and caterpillars, and also has some effect on beetles such as bean weevils and other leaf eating pests. The species of most use for most farm applications is sp israelensis, which is selective for dipterans and may also have some effect on fleas/ticks (studies are encouraging but other strains may be more effective).
There are a lot of different bT strains, all of which produce their own unique toxins. Theyâre not toxic to anything other than the target species, and the toxin will break down organically as itâs present naturally in the environment, which makes it a very safe choice environmentally.
dungrulla, thanks. I think this clarification helps someone who might end up at their big box in the garden department and get the wrong variety of Bt. I am a Master Gardener so more familiar with Btâs use on caterpillars than I am fly larvae 
Iâm fairly new to this but VERY into insects/spiders since I keep tarantulas as pets and grow my own feeders for my tarantulas and reptiles. I do a lot of research on control mechanisms and the methodology weâre using this year is new to me, but seems to be working VERY well. My trainerâs barn is beginning to have flies and we donât have any. I also havenât had any mosquitoes, and barely any of those little annoying gnats. All of them are dipterans. Before we started this control method we had one warm night and I came in with about 15 big mosquito bites.
There are scary labels on most of this stuff but bT is truly harmless to non target species and is sold for use in stock tanks so I have no qualms about spreading it on pastures or putting it in bedding and manure piles.
Bt is usually the biological reference. The genus is capitalized while the species is lower case
As a Master Gardener, I really only comment on pests found in the garden, not in barns or homes or vehicles etc as that is where my education focused (garden plants and pests)
A well executed IPM can be very successful depending on the pest Glad that youâve landed on a strategy that works for you. :encouragement:
Sounds crazy but do you have any new construction close to your farm? Movement of earth/dirt can contribute to more flies. You may want to double up on the fly predatorsâŠa.e. get them twice as frequently this first season. Fans should help too. Are there cows nearby??
Muscovy ducks. We have four ducks and NO flies in the barn.
Hard to believe I know, but true.
When I used fly predators I put them in the field and manure piles. We just composted our manure. If you put them in the stalls they end up there anyway.
Those were the instructions some 15+ years ago for my barn in CT. They do take a while to work but once they are established they work great.
Yes for ducks! Iâve seen them snap mosquitos out of thin air.
Agree. Most of my horses are on a low NSC pellet, but occasionally I have a hard keeper and feed a Senior feed. Although itâs still pretty low in NSC, it does attract flies to the feed tub, and that horseâs manure is always blanketed in flies. But when I donât have a horse on Senior feed, I donât have a fly problem at all.
I tried fly predators for 2 years and they did not help at all. In fact the second year the flies were worse than ever. The only thing that has made a difference is putting in a Pyrahna fly system. It cost about $1100 the year I bought it and installed it myself so no costs there ( except for my paid helper that carried around the ladder and whined). It seems like most of the people that say that fly predators work live in a dry environment. I am in the HOT, muggy southeast where it rains a lot and I think there are too many breeding places for flies that I cannot control. Plus they do not work on gnats,deer flies, large stable flies, etc. The best refuge for my horses is a clean stall with a fan and fly spray misting on them several times a day. Is this ideal? maybe not but the only thing that works here.
Wow, I have had great luck with fly predators for the last 20 years. The key is to start early in the cycle. Donât wait until the flies appear! Order more than you think you need. And place them on fresh manure. All my horses live out 24/7, so I do not have the convenience of a manure pile. So I place predators in the shed and wander around the field looking for fresh manure. Fortunately I have a stallion who is proficient at creating lots of piles of manure for marking purposes. As I said, my farm is largely fly free and my horses donât have to wear fly masks.
I had no luck with fly predators. I use this stuff once a day after the morning stall mucking.
https://www.valleyvet.com/ct_detail.html?pgguid=dd88e107-8e21-4224-98d9-a9a11ab51cd9
I also clean stalls 2 to 3 times a day and keep my manure pile well, well away from my barn.
