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Ford County

Late Season Fly Control

Horn flies are blood feeding flies that impact production on cattle operations. Populations of these flies tend to peak in June. The hot dry days of summer tend to decrease the overall population. However, in late-August to September as the temperatures begin to decrease and humidity increases, the horn fly population tends to peak again.

The common classes of fly control products are: pyrethroids, organophosphate, macrocyclic lactones and insect growth regulators. These products are approved to be used by a number of different application methods. So understanding of the product label is very important.

Classes of fly control products and chemical names:

  • Pyrethroids:
    • fenvalerate
    • permethrin
    • cyfluthrin
    • lambda-cyhalothrin
    • zeta-cypermethrin
    • bifenthrin
    • deltamethrin
  • Macrocyclic Lactones:
    • abamectin
    • eprinomectin
    • ivermectin
    • moxidectin
    • doramectin
    • spinosad
  • Organophosphates
    • diazinon
    • coumaphos
    • pirimiphos-methyl
    • chlorpyrifos
    • phosmet
    • tetrachlorvinphos
  • Insect Growth Regulators (IGR)
    • methoprene
    • diflubenzuron

Many producers use insecticide impregnated fly tags to provide fly control for the majority of the grazing season. It is important to note what class of ear tag is used on a yearly basis. Resistance is a real concern and proper steps should be taken to help mitigate it. Several generations of flies occur during the grazing season. During the multiple generation turnover, flies do develop some level of resistance in continued presence of a parasiticide. It is important to remove spent fly tags once they have lost their efficacy. The sub-therapeutic levels of product left in the tags hasten development of resistance. It is also recommended to switch class of fly tag (not just brand) on a yearly basis.

If placed too early in the season, the fly tags will lose potency and efficacy late in the season when the fly burden will be peaking once again. Depending on the tag, length of expected efficacy may be 3-5 months. So extra steps may be needed when the fly tag loses its effect. This late season treatment after the fly tag has run its course can be extremely successful for a number of reasons. Changing the class of parasiticide at this time, and using a spot-on/spray treatment will reduce the number of resistant flies that overwinter. AS well as reducing the overall population in the area. This helps continue the success of the fly management product rotation from year to year. The spot-on/spray products are shorter acting (2-4 weeks). Since they have less residual activity, they carry minimal risk of developing resistance when used at this time.

Administering spot-on/spray products does require additional labor. For spot on products, the cattle would need to be worked through a handling facility for proper administration. Sprays can be applied a number of different ways. Be sure to read the label instructions for proper mixing directions. The spray itself can be applied by something as simple as a hand held sprayer or an electric spraying on the back of an ATV. Some producers prefer walking through the herd with a hand held sprayer after acclimating the cattle to their presence.

With flighty cattle, gathering the group into a holding corral and spraying the product on the cattle as they exit the area may be the only viable option. This ensures consistent product delivery without having to catch each individual animal in a chute. High volume high pressure application can also be utilized in a holding area, but larger pumps and tanks are needed which can be an issue in the pasture setting. Cattle rubs are another option, but are most successful when cattle are all move under or through a controlled traffic area (such as controlled entrance to water and mineral areas). Many cattle will not use these rubs in a pasture setting without incentive and application would not be consistent through the herd. So the controlled access areas are very important.

Timing of application and product use are always important topics to review with your local veterinarian to develop a site specific pest management plan. For more information, contact A.J. Tarpoff at tarpoff@ksu.edu.