Fly Control Methods

Spring is now here both on the calendar and as signaled by the signs of nature. The pastures and wheat fields are greening up and growing, trees are blooming and leafing out, spring born calves are hitting the ground, and the flies are swarming…

Flies cause a good deal of losses to cattle producers each year in several ways. They spread blood borne diseases such as anaplasmosis, can help carry pink eye from one animal to another and are an all-around nuisance to cattle and humans alike. People and livestock have been entangled in a never ending battle with the pesky little creatures since the dawn of days. They are quite resilient and adaptable making them impossible to completely eradicate, however, science has come up with a few products to gives us a leg up in the battle against flies, reduce the impact on the pocket book and the distress level our cattle go through because of them.

There are several species of flies that bother cattle, however, most problems are associated with three types, 1) Horn Flies are a small fly, only about half the size of a common house fly but they cause millions of dollars in losses to cattle producers each year. They tend to congregate over the back and shoulders of cattle leaving only occasionally to lay eggs in manure piles. They economic threshold level for horn flies is 200 per mature animal.  2) Face Flies congregate on the face of cattle, surviving by sucking on the secretions of the eyes, nose and mouth of cattle; because of this, they are common transmitters of pink eye from one animal to another.  3) Stable are a piercing blood sucking fly much like the horn fly however they are closer to the size of house flies and have an economic threshold level of only 5 per front leg.  Several studies have shown that at a level of only 5 stable flies per front leg, is great enough to cause a reduction in feed efficiency that would cost $8.51 over the course of the fly season. 

Several topically applied compounds have been readily used for fly control in barns and on livestock for decades now.  They are sold under a wide array of tradenames and have been formulated for use by several methods. Most fall into two broad families of insecticides, pyrethroids and  organophosphates. One of the first application methods used was “dusting” where a powder form of insecticide was either placed in a hanging bag in a high traffic area where cattle would commonly come in contact with it dusting the insecticide onto them or applied using some sort of duster directly to the animal. Much like the dust bags, liquid               solutions are available that are mixed with some sort of oil and soaked into a large sock like back rubber to apply the insecticide to the cattle. Using secondary hang down cloth or fly bullets will increase the effectiveness of the rubbers on face flies. Both dust and liquid soaked applicators can combat face and horn flies well if placed in high traffic areas such as hanging on mineral feeders or over water tanks. Another  commonly used topical method of fly control is with various spray applications. Spray applications can be effective; however, it can be labor and time consuming to get an adequate amount of insecticide on every animal in the herd.  Compounding this is the fact that spray on alternatives tend to be relatively short lived and must be reapplied fairly often through the season.     

Another option that has been around for several years now are ear tags treated with insecticides to reduce the fly load on the animal. Most fly tag manufacturers recommend having a tag in both ears on mature cattle and one ear on smaller calves.  The tags have a life of 3-5 months and do a fairly good job of keeping flies away. Like topical treatments, fly tags generally use either organophosphates or pyrethroid compounds to keep flies at bay. Fly resistance to all of the topically applied and ear tag options can and will become an issue.  Because of this, it is recommended to switch up classes of insecticide from time to time to reduce the likelihood of resistance issues. With tags, it is advisable to cut the tags out and discard them as soon as a decline in their performance is seen to keep resistance at bay.

Pour on treatments are an available option that  control flies and other external parasites with labeled effective control ranging from a matter of a couple of weeks to full season long treatment with one application. Most of the chemicals labeled for pour on application are members of the pyrethroid family of insecticide, similar to spray applications; they do however tend to have a little longer life span than spray on methods.  For those of you using a spring parasite control method such as ivermectin, you get the added benefit of fly control for up to a month depending on application timing and weather conditions. 

Over the last decade, feed through options that control flies by way of interrupting egg production in manure have gained traction in the fly control market share. These products are often labeled as IGR or Insect Growth Regulator on a feed tag.  The most common for cattle on pasture is S-methoprene sold under the name Altosid. Altosid is labeled for the control of horn flies but not face flies. Another IGR product available, diflubenzuron, controls both horn and face flies. Diflubenzuron is available as a feed additive form as well as a slow release bolus. IGR products have proven quite useful as there hasn’t been any reported incidence of fly resistance yet.  For most effective results, the product must be used beginning 30 days before fly season begins until 30 days after the first killing frost in the fall.  This normally equates to a period starting mid-March and going through mid-November. IGR products are as simple as purchasing and using mineral or lick blocks with the product in them and are quite effective at controlling flies, they do have the drawback of only controlling flies in the area where the products are used. In order to reduce fly pressure from surrounding herds, try and keep close contact to a minimum as much of the time as possible.

When selecting fly control methods, there are several factors to consider. For effective control year after year, a long term plan involving several different methods and product types is necessary. Even in the same year, rotation of insecticide classes can become a necessary precaution to prevent resistance to any one product type. Unfortunately, there is no silver bullet cure all products that be 100% effective in every situation.  Using multiple products and application methods continues to provide the best results.

Source: Andy McCorkill,  Livestock Specialist