Horses

Horses
In summer 2007, I monitored catches of biting flies in an 8-week experiment comparing four cloth /netting variations of octenol-baited Nzi traps. The traps were set about 50-m apart on a farm at Edwards, Ontario (near Ottawa, 9 km north of Russell), starting in mid-June. The traps were set near a barn (with two horses and five goats) on a transect extending into a pasture where the horses grazed. The total catch was 41,841 tabanids (mostly horse flies); with an average catch of about 1,300 tabanids per trap per week.
The maximum weekly catch in a single trap was 3,155 tabanids at the end of July; mostly Tabanus quinquevittatus). The photo is of a Nzi trap made from Top Notch Blue #563 marine polyester canvas. This relatively new product appears to be a good option for traps, with catches similar to, or better than, Sunbrella Pacific Blue, #6001 acrylic awning canvas. In relative terms, Watson et al. (2007) captured about twenty times fewer tabanids per trap per day in a similar test over two summers using the HorsePal® and Epps® traps set near horses on two farms in North Carolina. My total catch in Nzi traps at the farm in Ontario in 2007, with from 2-7 traps set at any one time, was 55,515 tabanids and 7,919 stable flies over 559 trap days of effort. Watson, D.W., Denning, S.S., Calibeo-Hayes, D.I., Stringham, S.M. & Mowrey, R.A. (2007) Comparison of two fly traps for the capture of horse flies (Diptera : Tabanidae). Journal of Entomological Science, 42, 123-132. It's hard to interpret differences in catch among traps from different areas without direct paired comparisons, but the catches in Nzi traps near horses in Ontario can clearly be very, very large. Note that partial results from the publication of Watson et al. (2007) appear to have been posted on the web in the North Carolina Pest News. Except for this work, there is very little published on the performance of tabanid traps in applied settings near animals.
Below are a few more insights into trap performance from other exploratory work conducted near horses on the other side of Canada in dry prairie environment in southern Alberta.
	In September 1999, I monitored catches in an unbaited Nzi trap next to four horses near Moon River Estates (30 km west of Lethbridge). This survey coincided with a period of high stable fly density monitored with another Nzi trap at the AAFC dairy in Lethbridge. The horses were kept next to a rural, residential area in a river valley, surrounded by crops and grassland. The trap was set quite late in the biting fly season, and hence, horse flies and biting midges were not present.
An adaptation of the web instructions for making "Do It Yourself" Nzi traps was published in Volume 6, Issue 4 of Natural Horse Magazine. A brief article on the traps horse owners use for biting flies was published in the August, 2007 Newsletter of the Rusty Stirrups Riding Club "Poop Scoop". Feedback on other people's experiences using the trap near horses is welcome smihok@rogers.com Unbaited traps will catch horse flies, but catches will be improved with an octenol lure. People with horses should also consider baiting traps with aged horse urine. Krčmar et al. (2005) showed recently that aged horse urine was attractive to horse flies in Croatia, greatly increasing catches in traps. This is the first time anyone has tested this bait. There is lots of potential for further work to identify which types of urine from which animals are useful and which are not. So far most work has only been done with cow urine. See the detailed section on attractants. Krčmar, S., Hribar, L.J. & Kopi, M. (2005) Response of Tabanidae (Diptera) to natural and synthetic olfactory attractants. Journal of Vector Ecology, 30, 133-136. [article can be downloaded at the journal web site sove.org] In autumn horses are often bothered by face flies, Musca autumnalis. The Nzi trap is good for biting flies, but catches few house/face flies. Hence, it is unlikely that setting a trap near horses will provide any practical relief. Nevertheless, this approach has yet to be tested in an area with many nuisance flies. Horses are also harassed in certain areas by very small biting midges (Culicoides). In these areas, it may be useful to make Nzi traps with fine mesh netting ("no-seeum" net) instead of mosquito netting. Unfortunately, this type of netting is somewhat opaque; this substitution typically reduces catches of stable flies and horse flies by about 30-50%. Small changes like this to basic trap materials have yet to be investigated in detail and may be worth some simple comparisons in areas where other insects are serious pests.

In the survey at Lethbridge, a single Nzi trap caught many stable flies, and a few horn flies. Other nonbiting flies associated with animals/dung (especially small flies of the family Anthomyiidae) were also caught. Up to 150 Stomoxys calcitrans and 12 Haematobia irritans were caught per day. Owners considered biting flies to be a major problem in mid-summer. They also spoke of early-season problems with very small flies (likely biting midges), but were unable to be more specific. At the time of trapping, some horse owners were still using insecticides for "fly" control.


G. haemorrhoidalis (female)	The trap also caught small numbers of male and female horse bot flies, Gasterophilus haemorrhoidalis and G. intestinalis. Up to four were captured per day. Horse owners were unaware that these parasitic flies were related to the larvae they observed in dung. In this moist, riverine setting, the trap also caught two common mosquito pests (Culiseta inornata and Aedes dorsalis). Up to 20 were captured per day.