MT. VERNON, Mo. Think how much aggravation 200 flies biting and flying around you would create. No wonder research shows that blood-sucking horn flies can reduce calf weaning weights by up to 20 pounds and reduce gains on stocker cattle by 25 pounds per head when flies are not controlled.
The threshold level for economical fly control begins around 200 flies per animal according to Eldon Cole, a livestock specialist with University of Missouri Extension.
“Counting flies isn’t easy so most of the estimates are made using the assumption that if there’s an area of flies on the animal the size of the palm of your hand that’s roughly 50 flies,” said Cole. “I’ve assisted with a field trial that involved using binoculars and actually counting flies early in the season when they weren’t too numerous and it is easy to get 200 flies per animal.”
In addition to horn flies, horse flies, stable flies and face flies may create problems for cattle as the summer goes on. Each of these creates a unique problem for animals and are difficult to control according to Cole.
“The routine control measures for horn flies will only have limited success with the other fly species,” said Cole.
Sprays, insecticidal ear tags, dust bags, back rubbers, pour-ons and oral larvacides are the controls used on horn flies.
“There is even research supporting biological control with fly predators, but they work mainly in densely populated cattle areas such as feedlots,” said Cole.
Another interesting point in cattle fly control is that some animals seem to be less susceptible to flies than others. Researchers are looking at this from the cattle’s genetic resistance standpoint. It could involve hair density, hair color, sex of the animal, hide thickness, etc.
“As you work with your herd you may observe that some cattle attract more or significantly fewer flies than others,” said Cole. “Most of the fly control methods for horn flies do work. However, cost, convenience and length of control must be considered.”
For more information on fly control in beef cattle, check out the Missouri Beef Resource web site at http://agebb.missouri.edu/beef/index.htm. Three MU Extension livestock specialists are also available in southwest Missouri and can be reached by telephone: Eldon Cole in Mt. Vernon, (417) 466-3102, Gary Naylor in Dallas County, (417) 345-7551, and Dona Geode, in Cedar County, (417) 276-3313.
Deciding Which Horn Fly Control Measure is Best for you
Eldon Cole, a livestock specialist with University of Missouri Extension, says there are several things to keep in mind when deciding which horn fly control measure it best. Keep the following items in mind:
* Resistance to pesticides can develop so rotating each year or so between the pyrethroids and the organophosphates will help slow down the resistance buildup.
* Remove old fly tags at the end of their useful life. Leaving them in aids in fly resistance buildup.
* Many fly tags are still effective, but frequently are put in too early in the season. Rotate the active ingredient used in the tag from year-to-year.
* Backrubbers or dust bags are highly effective and economical, but they require regular management to make sure cattle use them.
* If you’re fortunate enough to have a supply of wire and burlap bags you can make your own rubber at a significant savings. Old flannel material will work in place of burlap.
* Feed-throughs offer convenience, but cost more per day or month. They are most effective when consumed by all cattle in a fairly large area. The additive interrupts the life cycle of the horn fly in the manure pat.
* Combining horn fly control tactics may be helpful to give the cattle maximum relief. Remember you’ll never have totally fly-free cattle.
* Face flies are generally not resistant to pesticides and insecticidal ear tags and other control methods for horn flies are effective against them.
* Treatment costs per head per day can vary from a couple of cents up to 8 to 10 cents depending on method and expected length of effectiveness.
For persons not wanting to use pesticides, University of Missouri Extension does have plans for a walk-through fly trap (that reduces flies up to 70 percent) that can be located where cattle pass through it daily. Ask the nearest MU Extension Center for guide sheet 1195 or find it online at extension.missouri.edu.
Source: Eldon Cole, University of Missouri Extension