As the weather warms up, it’s not too early to start thinking about fly management programs.
Jonathan A. Cammack, Oklahoma State University Cooperative Extension Service Livestock Entomology & Parasitology Specialist, says horn flies should be approached from multiple angles.
“A two-pronged approach of combining insecticide products targeted at different life stages, such as an ear tag for adult control, and a feed-through insect growth regulator (IGR) for larval control, will give you the highest probability of success in the battle against these pests,” Cammack explains.
Ear Tags
Ear tags are an effective method for the control of adult horn flies. Cammack recommends waiting to tag animals until horn fly numbers reach the threshold of 200 flies per animal to help ensure the ear tags are still effective into peak fly season in mid to late summer.
Most ear tags have an effective life of approximately four months, under ideal conditions. Weather can affect how long they last, so during the hottest days of summer the lifespan of an ear tag may be three months or less, Cammack adds.
“It’s never too late to tag, but it can be too early,” he says. “Make sure to use a different chemical class than you did last year, to help slow the development of insecticide resistance.”
When picking a synthetic pyrethroid tag, choose one that is synergized, and contains piperonyl butoxide (PBO) as an active ingredient, he says.
IGRs
IGRs help manage larval horn flies, and larvae of other biting and nuisance flies that develop in decomposing organic matter such as manure.
“Feed-through IGRs are consumed by the cattle, and pass through their digestive tract and are excreted in the manure, which serves as a food source for larval flies,” Cammack explains. “When the larvae consume this IGR in the manure, they will not successfully complete their development to the adult stage.”
Cammack recommends to start feeding minerals or supplemental feeds containing IGRs during the month of March and continue through October.
“We want to make sure all of the manure in pastures contains the IGR, so we can start to have an impact on developing fly larvae (particularly horn flies) as soon as the adults become active and start laying eggs in the manure, and throughout the remainder of the fly season.”
Products that are registered as feed-throughs for cattle contain one of two active ingredients:
- Methoprene (examples: Altosid® IGR, Dipteracide®, Pertinent IGR)
or - Diflubenzuron (examples: ClariFly®, JustiFly®, HerdGuardTM)
“If you have been feeding your cattle hay over the winter, it is likely that the hay, manure, and urine mixture surrounding your round bale feeding sites is a breeding site for stable flies,” Cammack says. “During the spring, as it starts to rain more frequently, this wasted hay can remain wet, and continues to be a source of development for stable flies.”
For these instances, premise granular IGR products can be spread around on top of this wasted hay surrounding the round bales. The granular products dissolve and come into with or are consumed by larval stable flies and prevent their development to the adult stage, Cammack explains. Examples are Novaluron (ExhaltTM WDG) and Cyromazine (flynexx® granules).
“Taking the two-pronged approach can help minimize the impacts of horn flies and other nuisance and biting flies on your herds,” Cammack says.
