Old School Cool
By : Heather Smith Thomas
Traditional Methods Can be Useful Fly Control for Beef Cattle
The battle against flies is constant during warm weather, but there are several ways to reduce these pests.Though there are some new methods (pour-on products, insecticide ear tags, special fly traps, and a “gun” designed to shoot a ping-pong ball size “bullet” of insecticide onto a cow from a safe distance, just to name a few), some of the more traditional methods are still useful. The old style back rubbers, oilers and dust bags can help fill some gaps in a fly control program.
Roger Moon, PhD, Professor Emeritus, Entomology, University of Minnesota (St. Paul), says it’s important to know which flies you are trying to control, and utilize the most appropriate tactics. “The flies that bother cattle in pastures are mainly horn flies, face flies, and sometimes stable flies. Stable flies may be coming from a nearby barnyard; they are generally not coming from the pastures unless there’s debris from old round bales or from hay/straw residue that was fed in winter, creating breeding sites for stable flies,” he says. By contrast, horn flies and face flies breed wherever there are fresh cattle dung pats.
Any cattle at pasture—cow/calf or stocker cattle—should be protected from high populations of flies. “Blindly treating with any topical insecticide (as might be applied via dust bags, back rubbers, etc.) will give some benefit by killing horn flies, but how long the product will be effective depends on historical use and how quickly the flies develop resistance,” says Moon.
“Historically we haven’t seen much horn fly resistance to dust bag products, but it may be simply due to modest amounts of use. Most producers didn’t use dust bags as well or as consistently as they could have. It’s a tradeoff. The sporadic use may not have been as effective, but also there was less selection for resistant flies,” he explains.
“These things go hand in hand. The more heavily and effectively you kill the fly population, the faster you select for resistance.” If most of the flies are killed, the ones that survive are the ones that are resistant to the insecticide and live to reproduce—and you end up with a greater number of resistant flies.
Back rubbers and dust bags were the original topical applicators. They work best in forced-use situations where the cattle have to come in contact with the products. The applicators must be placed where cattle come to water or salt/ mineral—in a location they have to pass through. If a dust bag is placed in a narrow gate, forcing the cattle to come into contact with the insecticide, they will all be treated daily,” says Moon. Some cattle voluntarily rub on an oiler/back rubber or dust bags, but many won’t use them unless forced to walk under them.
“These systems give good horn fly control but only modest face fly control. No topical product works very well against face flies. The difference is that horn flies live on cattle, whereas face flies only come long enough to get a sip of tears/ secretions from the eyes and then leave again. Very few of the adult face flies in a pasture are actually on the cattle, whereas almost all adult horn flies are on the cattle.”
It’s important to treat cows for flies, but not necessary to treat the calves. “Treat the cows, following dose recommendations on product labels (whether ear tags, pour-on products or dust bags), and if there are calves with the cows they’ll get some protection. Calves will benefit just being near (and in contact with) an adult that’s been treated. This is what we call the herd effect. Additionally, treated cows produce more milk, which benefits their calves,” says Moon.
The oilers, back rubbers and dust bags need to be maintained, refilled as needed. “Check them periodically. If it’s a dust applicator, tap it with a stick and see if a little dust comes out. If it gets wet and caked, or empty, it won’t work. Most of the dust bag designs I’ve seen have some type of waterproof covering, like an apron or tent on top, to keep the dust dry,” he says.
Back rubbers utilize a carrier oil. “Some ranchers use diesel, and others use soybean oil or some type of vegetable-based oil. The insecticides are oil-soluble and carried onto the hair coat with the oil.”
If the product is a pyrethroid (which are mainly permethrin) don’t get it into a water source. “If you get it onto the cow it will stay on the cow, but you don’t want any spilling into a stream, or where runoff might carry it into the water, since these products are toxic to fish. Just be in compliance with the label,” says Moon.
The traditional backrubber applicators were in use more than 70 years ago. “Bill Rogoff, a USDA entomologist, invented the back rubber. He strung a piece of chain across an alleyway at proper height for cattle, wrapped it in burlap and saturated it with oil, which wicked the oil and insecticide onto the cattle.” Oil spreads through the hair coat and diffuses onto the whole animal, taking the insecticide with it.
Another type of applicator utilized bags of insecticide dust in a tent apparatus over a salt/mineral feeder. When cattle stuck their heads into the feeder the dust was applied over their head, neck and withers. As long as some of it gets onto the animal, it spreads through the hair coat when she slings her head around to knock flies off her sides and back or to other animals as they stand head to flank. In this way the cow also gets some of it onto her calf.