With 350 species of horse flies in North America, no area of the country escapes this plague. And the horse fly is no sissy. The female is responsible for the transmission of equine infectious anemia (EIA—the thing Coggins tests look for) and for the painful biting and blood-sucking action that drives your horse crazy. She laughs at herbal repellents. Even heavy-duty chemical sprays are but a brief deterrent. Download a PDF of this article here.
A single female horse fly lives for about four weeks and produces five to six batches of eggs, with each batch containing between 100 and 1000 eggs. That’s scary. If you could just locate those females and wipe them out, your horse would have a much more enjoyable summer. Fly traps can help you do that, and we found two good choices.
The Horse Pal fly trap works on the theory horse flies are “sight feeders.” This means they find their victims by recognizing their shape. The Horse Pal’s large, swinging shiny ball looks (to a horse fly, anyway) like the rear end of a horse. You might laugh, but we’ve caught a bunch of flies in that trap.
The EPPS fly trap operates on a similar principle, except the horse-like components are large black sheets of polypropylene tarp with open areas underneath, much like the side of a horse might appear to a horse fly.
The Horse Pal traps the flies in a clear jar at the top of the escape route where they decompose in sunlight. The EPPS uses plastic panels that deflect the escaping flies into water where they drown. The water is treated with dish soap, breaking the surface tension of the water and preventing the flies from swimming out of the catch pan.
Placement of the traps is important, as you want to target the prime spots. We placed the traps near where the horses normally congregate, with mown grass underneath, and safely out of the reach of curious equines. Most importantly, there was a good “sight” line, away from woods, buildings or obstructions.
The EPPS maker claims it will trap one pound of horse flies a day and 80% of all biting flies. The Horse Pal manufacturer makes no numerical predictions, although we had used that trap for several prior years.
Horse Pal sent us an unpublished two-year study by Mike Stringham, an entomologist at North Carolina State University, that showed Horse Pal and EPPS caught similar numbers of flies the first year. The second year, the Horse Pal caught more flies than the EPPS. However, the study does not state whether or not they replaced the plastic deflectors on the EPPS for the second year.
The EPPS trap requires regular attention. You need to keep the trays filled with water and dish soap, and you must remove dead flies every 48 hours.
This is a slightly revolting task that can’t be ignored. If the dead insects start piling up, the dazed flies—apparently recovering quickly from the traumatic brain injury sustained when ricocheting off the plastic—can use the accumulating insect bodies to escape their watery death.
Finding the most productive trapping spot is a challenge, but both manufacturers agree that nothing’s more important. Be prepared to experiment. The difference of even just a few feet can dramatically change your results. Both traps claim to attract deer flies, but we never caught any, as our traps were placed well away from wooded areas, as instructed.
In an attempt to see exactly how important placement was to catch volume, we loaned out the original Horse Pal to a horse owner who reported she had many horse and deer flies. She reported poor catches, in spite of moving the trap to several locations on her property. However, when we investigated further, we noted that there was an active machine-repair shop on the premises, and fumes like these will discourage flies in the area. This reminded us how important location is in setting the trap.
We noted many more horse flies around our horses when they left the trapping area and came down to the gate to be stabled for the night. We thought moving the Horse Pal to the gate area would take care of that problem, but we trapped only a few. When the horses left the area, so did the flies, underlining the importance of placing the traps near the herd’s normal loafing spot.
Both these traps will, with consistent proper use over the years, reduce the overall number of horse flies on your property. We believe they are worth the investment.
If you decide to invest in a fly trap, figure out if you have an ideal location for trapping and if you’re willing to do whatever it takes to find one. Nothing is more important in catching flies than location.
Next, ask yourself how much time you’re honestly willing to spend on maintenance. If you’re a “set it and forget it” type, Horse Pal is for you. If all that matters is body count, and you don’t mind tending to the trap every day or so—and going through the effort of moving it until you find the ideal trapping spot—the EPPS might be the one for you.
When all’s said and done, we admit we are the “set it and forget it” type, so the Horse Pal is our top choice.
Article by Beth Benard, Horse Journal Contributing Editor