Profit Drain

One-Two Knockout for Flies

Rotate insecticide classes on sprays or pour-on products every one to two years, along with ear tags. The right treatment combination can maximize control and minimize resistance problems. (DTN/Progressive Farmer photo by Jim Patrico)

Flies are never easy to ignore. Scott Warren says without a good control program, fly populations would explode in the 1,000-head commercial cow herd he manages at North Carolina's Buffalo Cattle Company. During the years, he's come to rely on a combination approach, a one-two punch, to control horn and face flies. It includes a feed-through insect growth regulator (IGR) in his mineral mix and a pour-on insecticide.

Horn flies are one of the cattle industry's biggest profit drains. These bloodsuckers have a direct impact on milk production and weight gains.

"If horn flies get out of control, our cows bunch up in the pasture and swat each other with their tails. They aren't grazing, and their milk production drops off," Warren says.

MORE POUNDS

University research shows effective horn fly control adds 12 to 20 additional pounds to a beef calf at weaning. Based on today's prices, that's $19 to $32 more per calf.

Warren calculates he's getting at least 20 additional pounds on his calves. Not only do they gain more from the increased milk production, but the calves also feed at mineral stations, getting the direct benefit of the feed-through control.

Face flies, known to travel more from animal to animal and even farm to farm, bring a different type of problem. They are known carriers of the bacteria that causes infectious bovine keratoconjunctivitis, commonly known as pinkeye.

It's the most prevalent infection in breeding beef females and often leads to as much as a 36- to 40-pound loss in weaning weights.

In addition to weight loss, there is generally a steep price discount when selling a calf with pinkeye. These discounts range from $12 to $120 per head on a 600-pound calf. Feedlot buyers shy away from animals with pinkeye because of treatment costs and depressed weight gains.

BAD BACTERIA

Moraxella bovis is the primary bacteria that causes pinkeye, but there are multiple strains. Weaned calves won't graze and gain weight as effectively with pinkeye. A case of pinkeye in one eye can reduce a calf's weight gain by an average of 17 pounds; in both eyes, it can be as high as 65 pounds.

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Warren's program uses an IGR mineral with Altosid (methoprene) available to cattle mid-February through October. Labels recommend beginning IGR treatment 30 days before fly season starts. IGRs don't kill horn flies, but they prevent larvae from developing to maturity in manure. This essentially interrupts the life cycle of these flies.

Pour-on insecticides are Warren's backup for the IGR feed-through. He waits to use pour-on insecticides until fly populations are building in midsummer. He's had success using Ultra Saber (Lambdacyhalothrin with piperonyl butoxide) and Ultra Boss (5% permethrin and 5% piperonyl butoxide). Depending on the fly population, Warren may use pour-on treatments every 30 days to supplement the feed-through.

THE EAR TAG CHOICE

For brothers Andy and Jason Smith, ear tags are still the way to go on their 470-brood cow herd, near Oxford, N.C.

The two run Granville Farms Inc. Cows calve in December and January, which puts weaning time around August. Calves are sold in September.

"This puts the most critical time for our cows making milk during the worst fly months. Insect control is a major concern," Andy says.

One key to the Smiths' continued success is a program that rotates fly tags between classes of insecticides (pyrethroids and organophosphates). This rotation helps prevent flies from building resistance to one class of insecticide. When fly populations peak, they also spray insecticides to knock down numbers. At the end of fly season, tags are removed to prevent resistance buildup as the insecticides lose strength.

"We've been using ear tags for several years, and we'll stay with those this year, along with using Co-Ral Fly and Tick Spray [organophosphate] or CyLence Pour-On Insecticide [pyrethroid]," Andy says.

TIPS FOR TAGS

Ear tags are still the go-to fly control for many producers. To keep them effective requires rotation and timing.

North Carolina Extension livestock specialist Paul Gonzalez says producers should rotate insecticide classes on ear tags and use the recommended number of tags per cow—often this is two. Check the label.

"I think timing is the biggest problem. Most tags say they will give you up to five months of protection, but three months seems a more realistic time frame in our area," Gonzalez says.

Producers who wean calves in April and May often put fly tags on cows at the same time. But in many areas, this will mean the tags have lost effectiveness by the time flies are at their worst, June through early September.

Ear tags should only be used once the economic threshold has been reached for flies. The rule of thumb is 200 flies per cow. A good gauge is the image that two hands will cover about 200 flies.

Gonzalez doesn't recommend rotating insecticide classes on sprays or pour-on products during the season. Rather, he says switch classes on everything -- ear tags and sprays/pour-ons -- every one to two years. Using the same class of chemical for both types of treatment means flies have greater susceptibility to the new class of insecticide when you switch.

Always remember to remove ear tags. Leaving them on is a fast track to resistance.

"Remove fly tags after the first killing frost. Even better, if you find a tag that works for you, be sure to remove it as soon as the fly season ends," the livestock specialist says.

FEED-THROUGH TACTICS

Feed-through fly controls need to be eaten by cattle for the insect growth regulators to do their jobs. Here are a few tips to improve consumption:

-- Use location to help manage mineral intake. To increase consumption, position mineral feeders in areas where cattle gather, such as watering points or shady areas. To decrease intake, move feeders farther away from these gathering areas.

-- Keep track of consumption. Some brands of minerals are eaten better than others. Knowing which ones are more appealing to your herd means you are getting your money's worth.

-- Keep mineral dry and protected from rain.

-- Maintain fresh mineral.

(AG)

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