Last month’s Regional Roundup discussed feed additive options to aid in horn fly control and some differences among horn, stable and house flies. This month’s roundup will focus on topical insecticide options and considerations to help control horn flies.
Topical insecticides can be applied to cattle using several different methods including eartags, pour-ons, sprays, rubs, dust bags and even a gel cap applicator. When selecting methods, consider how easy the cattle are to gather, how long the application may last, chemical classes available for an application method, cost and any other factors important to the operation.
To help slow horn fly resistance and improve efficacy of topical products, it is important to rotate chemical classes of active ingredients. Changing brands or application methods may or may not result in actually rotating chemical classes. Chemical classes of topical products include pyrethroids, organophosphates, macrocyclic lactones and insect growth regulators. Below is a list of some active ingredients that fall into the two chemical classes with the most products.
- Pyrethroids: Cyfluthrin, permethrin, zeta-cypermethrin, lambda-cyhalothrin, gamma-cyhalothrin
- Organophosphates: Coumaphos, phosmet, diazinon, tetrachlorvinphos
Recommendations for rotation schedules vary. In southern climates or areas with a longer horn fly season, consider rotating chemical classes halfway through the season or every 90 days. In areas with a shorter horn fly season, rotating chemical classes each year may be appropriate.
Piperonyl butoxide is added to some eartags, pour-ons and other products. It inhibits the breakdown of pesticides by insects, resulting in improved product efficacy. Piperonyl butoxide can also be purchased and mixed in solutions to use with sprays and rubs.
If it is not easy to gather cattle, insecticide eartags might be a good option, as they slowly release insecticide over a longer period.
Looking at the active ingredient can simplify product selection. There are many pour-on products available that all contain the active ingredient permethrin in either a 1%, 5%, 7.4% or 10% concentration. Application rates of these pour-on products will vary based on concentration so that regardless of concentration, the same amount of active ingredient is applied to each animal. Animal coverage will be greater with the more dilute products.
Rubs and dust bags can be used without gathering cattle. Effectiveness will vary depending on if and how frequently the cattle use these devices. From a Beef Quality Assurance (BQA) standpoint, vegetable or mineral oil should be mixed with insecticides instead of diesel for application.
