All these flies have in common that they do not bite, i.e., they do not suck blood of livestock or pets. Strictly speaking they are not parasites because they don't need the animals for feeding or development: they can easily survive without them. But some species can transmit diseases and all of them have a negative impact on the hygiene because they easily transmit bacterial contaminants all around in their environment.
They also have in common that livestock operations offer numberless places for egg laying and development: large or small fecal remains are virtually everywhere, as well as all kinds of decaying organic materials, food rests, abundant humidity, garbage, etc.
Most of these flies land on livestock or pets only occasionally: attracted by body fluids, dirt, feces, warm temperature, etc. Usually they remain only very shortly on the animals. For this reason it is not a good idea to treat the animals with insecticides to control non-biting flies: very few flies would be killed.
There are numerous types of baits: some of them are ready-to-use (e.g. scatter baits, powder baits, paper or cardboard strips impregnated with insecticides, etc.), others are liquid or solid concentrates that have to be diluted in water and/or mixed with some kind of food (milk, beer, sugar, etc.) before application on resting surfaces (e.g. as paint-ons) where the flies like to rest.
In addition to commercial products, there are numberless traditional home recipes for preparing fly baits without synthetic insecticides. If they work, there is no reason not to use them. Probably they won't solve serious outbreaks, but they can help diminishing the populations and will not select for resistance to insecticides.
Active ingredients used in fly baits
Most fly baits contain classic veteran insecticides with oral activity. They include mainly:
- Organophosphates (e.g. malathion)
- Carbamates (e.g. carbaryl, methomyl, propoxur)
- Synthetic pyrethroids (e.g. cypermethrin, permethrin)
- Neonicotinoids (e.g. dinotefuran, imidacloprid, thiamethoxam)
- Phenylpyrazoles (e.g. fipronil)
Most fly baits contain also a pheromone (usually tricosene) i.e. a specific sexual hormone of insects that attracts the flies to the bait. Many fly baits contain also some kind of bitter substance to avoid humans, especially children, or animals ingesting the baits.
The housefly (Musca domestica), which is the most important target for fly baits, is the world champion in resistance development to insecticides. There is virtually no chemical class of insecticides for which a resistant housefly strain has not been reported. Therefore it is essential to combine the use of baits with other methods that target the places where housefly develop, especially in order to eliminate or at least reduce all kind of manure and decaying organic materials in the facilities.
Pros and cons of baits
All baits have the advantage that they do not leave pesticide residues in meat, milk or eggs because they are not administered to the animals. They are especially appreciated and used in dairy farms and layer operations.
The major inconvenient of baits is that they do not control bloodsucking flies (e.g. stable flies) or other insects that may also infest livestock facilities (e.g. cockroaches, carrion flies, etc.).