Fly Zone

No two ways about it — the stress and energy loss caused by external cattle parasites result in fewer pounds of beef production. External parasites can be controlled by a wide variety and forms of products — ear tags, sprays, pour-ons, spot-ons, dusts, back rubbers and mineral additives.

Ear tags impregnated with organophosphate or synthetic pyrethroid insecticides to control flies and ticks were introduced in the early 1980s. Their first couple of years on the market, fly tags were among the hottest items on the livestock supply outlet order list.

But the use of insecticide ear tags for fly control isn't as simple as once thought, and today's beef producers shouldn't be cavalier about their application.

“The results of the fly tags can be very quick and dramatic,” says Larry Olson, Clemson University Extension beef specialist, Blackville, SC. “When used correctly, they can be one of the best pest management tools available to cattle producers.”

He talks about his first experiences with the use of ear tags for fly control.

“In some cases, 15 minutes after putting in the fly tags there were no flies on the cows, while clouds of flies hovered above them,” he says. “They worked great for the first year or two.”

However, many cattle producers found them to be complete failures the third year.

“Problem is, the fly tags often aren't used according to label instructions,” Olson explains. “Their improper use results in a buildup of resistance in the fly populations to the insecticide in the tags.”

With proper use and handling, he says, insecticide ear tags can still be a very effective and safe means of pest control. It just takes some attention to detail.

Rated the worst pest

Cattle pests, such as flies, cost cattlemen both in treatment costs and in lost production due to irritation by the pests and the diseases they cause or transmit, says John Maas, University of California-Davis DVM. In a survey of California cattlemen, Maas says face flies were rated as the worst pest, followed by horn flies and stable flies.

Face flies, in addition to producing eye irritation due to their feeding, serve as mechanical carriers of the causative agent of pinkeye in cattle — infectious bovine keratoconjunctivitis (IBK) caused by the bacterium Moraxella bovis.

“This condition consistently ranks as one of the five most costly diseases in California beef cattle,” Maas explains. “Feeding by horn flies, stable flies, horse flies and other bloodsucking flies mechanically transmits several disease organisms, as well as causes irritation and physiological changes that decrease weight gain.”

He adds there haven't been many new fly-control ear tags developed in the last several years, so preventing resistance in the flies is important.

Some reasons for resistance include:

• Using one fly tag/animal rather than a tag in each ear,

• Not tagging calves, and

• Applying tags too early in the spring.

However, Maas and Olson say the single-biggest contributor to ineffectiveness was failure to remove fly tags at the end of the fly season as recommended.

“Late-season flies in the fall, and early-season flies in the spring, were then subjected to sub-lethal doses of insecticide,” Olson adds. “As a result, they and subsequent generations of flies acquired resistance to the chemicals.”

If producers don't have a plan for alternating ear tags, they can find themselves in trouble, he adds.

“Keep records of which tags you use in any given year to avoid confusion over what ear tags to use the next year,” he says. “It seems like a simple thing, but we see a lot of wrecks with fly tags because producers couldn't remember,” Olson says.

Things to keep in mind

In addition to reading labels before purchasing and applying insecticide ear tags, Lee Townsend, University of Kentucky Extension entomologist in Lexington, lists the following points:

• All tags are labeled for beef cattle, but only those with certain active ingredients are approved for use on lactating dairy cattle. Check for any limitations for use, such as animal age.

• Look for the common name of the active ingredient (for example, permethrin). In some cases, different brands of tags contain the same active ingredient. You can save money by comparison shopping, or avoid inadvertently using the same active ingredient if resistance is a potential problem.

• Consider the recommended number of tags/head. Some brands call for one tag/animal, but research generally shows two tags/animal systems provide better face fly control.

• For fly control, it's best to tag animals after horn fly numbers reach 50 or more/animal side. This reduces the chances of flies developing resistance to the active ingredient being used.

Normally, tags provide 12-15 weeks of fly control. Tagging too early in the season can mean the tags won't provide sufficient control in the fall to help control the over-wintering population.

Townsend warns that because the insecticide concentration in the ear tags varies from 8% to 36%, they should be handled with caution.

“The tags are manufactured so insecticide is rubbed off the surface and onto the animal,” he says. “Any handling of the tags leaves some insecticide on the hands. The insecticide then can be transferred easily to the mouth, eyes, face or other body areas.”

Olson is a bit sterner in his warning.

“If you don't wear plastic gloves when using these ear tags, you're asking for trouble,” he says. “Don't touch your face when handling them, and be careful when disposing the used-up tags at year's end.”

The duo caution that insecticide recommendations may not be universal, and the use of some products may not be legal in your state or country. Olson says to check with your local county agent or regulatory official before using any pesticide.

Develop a fly plan

Both face flies and horn flies develop resistance to insecticides over time. For maximum prevention of resistance, John Maas, University of California-Davis DVM, has this advice:

“It's advisable to switch the class of drug you use each year or two,” he says. “If you used an organophosphate ear tag last year, use a pyrethroid one this year.”

Even better, he adds, is to follow up the use of a pyrethroid tag with an organophosphate spray the next year. Alternating the classes of drugs in this manner will increase the success of your preventive program.

Lee Townsend, University of Kentucky Extension entomologist, Lexington, notes three main types of insecticide ear tags based on the active ingredient(s) that they contain (see Table 1 on page 26):

• Organophosphate (OP) insecticides such as diazinon, fenthion, pirimiphos methyl, or a diazinon + chlorpyrifos combination. These tags provide good horn fly control and moderate face fly control.

• Synthetic pyrethroid (SP) insecticides — fenvalerate and permethrin are the original members of this group. Sold under a variety of brand names, they're usually less expensive than newer, more expensive synthetic pyrethroids, such as cyfluthrin, lambda-cyhalothrin, and zeta-cypermethrin. These tags provide good horn fly control and better face fly control than the OP tags.

  The insecticides in these two groups of tags attack the fly's nervous system in different ways. Seasonal rotation between an OP and an SP insecticide can help combat the insecticide resistance that's developed in horn flies in some areas.

  Resistance, indicated by a failure in horn fly control, can develop when tags containing the synthetic pyrethroid permethrin have been used for several consecutive seasons. No resistance to organophosphates, or the new synthetic pyrethroids, has been seen.

• Recently, a relatively new group of combination tags has appeared. These couple an OP and an SP in the same tag. Current examples pair lambda-cyhalothrin and pirimiphos methyl or cypermethrin and chlorpyrifos. The assumption is the OP would control SP-resistant horn flies.

Tags need to be removed at the end of the fly season in the fall to reduce the potential for insecticide resistance in both lice and flies.