There’s something new in fly control.
It’s a new chemistry, reported Dr. Kelly Loftin, University of Arkansas Extension entomologist.
“Pyrazole is a new class for livestock, although it’s been used in other areas,” Loftin told Ozarks Farm & Neighbor. “The trade name for it is Tolfenpro and the active ingredient is tolfenpyrad. Now, for the first time in the three years since organochlorines were taken off the market, we have four classes that can be rotated in ear tags – the pyrethroids, the organophosphates, the macrocyclic lactones and this new class.”
Loftin said whether to use tags or pour-ons depends on the producer.
“The advantage of the ear tags is simply if they time the treatment correctly, they may get by with that one application,” he said. “When producers put the tags in too soon in the fly season, in March or April, the tag can become ineffective by the time you hit the fall peaking population.”
Flies cause losses to cattle producers each year in several ways. They’re vectors of diseases, like pinkeye and anaplasmosis, but Loftin said the bigger problem is lack of weight gain, and the biggest threat is the horn fly. The pest can reduce calf weaning weights by 18 pounds or more, and they can reduce weight gain in stocker cattle by about 50 pounds in some cases.
“Several studies have shown that at a level of only five 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,” University of Missouri Extension Livestock Specialist Andy McCorkill told OFN.
In addition to ear tags and pour-ons, pesticides can be applied topically to cattle in a number of ways. Dust bags are placed in a high traffic area where cattle would commonly come in contact with them, or used to apply the chemical directly to the animal. Back rubbers are also used to apply the insecticide.
“There are also spray applications, but it can be labor and time consuming to get enough insecticide on every animal in the herd, even more so because they need to be reapplied fairly often throughout the season.
Another option that has gained popularity over the past decade has been the feed-through larvicide. Horn flies only lay eggs on fresh manure; these products interrupt egg production and are often labeled IGR or “Insect Growth Regulator” on the feed tag. McCorkill said the most common for pasture cattle is S-methoprene, which is sold under the trade name Altosid and is labeled for control of horn flies, but not face flies. Another, diflubenzuron, controls both horn and face flies and is available as a feed additive and a slow release bolus. He said the IGR products have not yet had any reported incidences of resistance, however, one drawback is they only control flies in the area where the products are used.
And the best fly control method, but the most difficult to master, is genetic selection of cattle for fly resistance. McCorkill said one study found about 80 percent of the flies distressing a herd were on only 20 percent of the cows. “Much of the research of genetics as a means of fly control was right here in the Ozarks, as part of studies conducted at the University of Arkansas,” he said. “The research concluded that the number of hairs per square inch of body surface was a likely contributor to a particular cow’s tolerance to flies.”
In-bred resistance is just one more tool in the box.
“For effective control year after year, a long term plan involving several different methods and product types is necessary,” McCorkill said.
