by Samantha Stanbery
Horn flies are on the way and cattlemen need to prepare a plan of action.
“Horn flies usually reach significant levels by late May to early June in Oklahoma,” says Oklahoma State University livestock entomologist Justin Talley.
Horn flies cause an estimated $1.36 billion in losses to the U.S. cattle industry each year. This results in a need for producers to implement fly control methods with a goal in mind.
“The primary goal is not to eliminate every fly,” Talley explains. “We try to maintain them so they don’t affect the animal in a negative way.”
The two ways to achieve this goal are through insecticides and management, Talley says.
Insecticides, like those used in ear tags and sprays, help reduce fly numbers and decrease stress on the animal. Practicing good herd management and having a good forage pasture system help reduce the impact of the parasites.
Talley recommends waiting to begin treatment until fly numbers reach a certain threshold.
“An animal with a decent body condition score can handle 200 to 300 flies without a negative impact,” Talley says. “For animals with a lower body condition score, I would recommend a threshold of 100 flies to reduce stress on the animal.”
Flies add stress by puncturing the skin of an animal 10 to 20 times a day, Talley adds. This stress causes a decrease in production areas such as milk production, weaning weights and average daily gain.
“Treated cattle gain 1.5 pounds per week more than non-treated animals,” Talley points out. “So consider the cost. It’s usually about $4 to $4.50 per head using two tags on an animal to get sufficient coverage.”
For treatment, Talley recommends a three-year insecticide ear tag rotation. Producers should use an abamectin product, or XP 820, during the first year. The second year should be an organophosphate tag, such as Warrior, Patriot or Corathon. A pyrethroid product — for example, Python, Python Magnum or CyLence Ultra — should be used in the third year.
Ear tags should be removed at the end of each fly season. If additional control is needed later in the season, use alternative methods of control — sprays, pour-ons, dusts or backrubbers — that are of a different insecticide class than the ear tag.
“We do this rotation to prevent insecticide resistance,” Talley explains. “Flies are genetically encoded to be resistant.”
Talley cautions against producers mixing products within a herd.
“Don’t tag half your herd with one product and the other half with another,” Talley stresses. “If they are in different pastures and never commingled, it would be OK but you need to be consistent for that whole herd.”
Talley also warns producers to be aware of older products which may be less effective.
Another alternative for fly control is using the VetGun system. The system uses a gun similar to a paintball gun and large gel capsules containing a pyrethroid product.
“This is a system where you will have to re-treat especially if there is significant moisture,” Talley says. “But it’s a good application technique and can be done easily.”
Another concern for producers is face flies which are the main problem for pinkeye. Face flies cause economic losses of $191 million per year in the U.S. cattle industry.
“Face flies are a major concern and are generally a problem for cattle producers in the Midwest, Missouri Valley, Minnesota and to the East Coast,” he says.
It is important to control these parasites because they carry the bacteria for pinkeye and scrape around the corner of eye in cattle, making them susceptible to infection, Talley informs. The treatment threshold for face flies in the eyes and around the muzzle is 10 to 20 flies per animal around midday.
Ear tags are a good control method for face flies, he added. However if a producer does not want to use tags, Talley recommends using a pyrethroid spray.
“Horse flies are another concern in areas where there are a lot of water resources,” he says. “They develop in semi-aquatic environments and are the hardest thing to control because only the female horse fly feeds.”
Horse flies cause an estimated $296 million in losses each year.
Talley recommends treating for horse flies with an insecticide to prevent major population outbreaks.
“There is no threshold established because they are so hard to control,” he says. “One can cause a lot of irritation to an animal. One may be OK but, if there are multiple flies, you need to use a product to control it.”
Stable flies are a concern in dairies, feedlots and pastured animals. It is estimated stable flies cause $672 million in losses each year.
“You can essentially manage stable flies by cleaning up old hay feeding areas,” Talley says. “Areas where hay accumulates is an ideal location for stable flies to develop.”
Talley suggests discing and running a rake through these areas to get them to dry out and minimize stable fly development.
As the fly season approaches, remember the goal is not to eliminate every fly, but to add pounds of beef in an efficient manner, Talley says. £