Insecticide impregnated ear tags contain one or more insecticides embedded in a plastic matrix. The insecticide ear tag was first developed in the early 1980s, and worked very well against horn flies. However within a few years, horn flies developed resistance to synthetic pyrethroid insecticides. To maintain efficacy, specific steps should be taken to manage resistance. These include: A) rotation of insecticide classes, do not use the same insecticide class year after year, B) withhold tagging until horn fly numbers reach 200 per animal, C) tag all adult cattle in the herd and with the recommended label rate, D) use alternative insecticides and application methods late in the season; and E) remove insecticide ear tags in the fall. Ear tags recommended are: Organophosphtes (Corathon,™ Optimizer,™ Patriot,™ and Warrior™) Synthetic Pyrethroid (CyGuard,™ Gardstar Plus,™ PYthon,™ PYthon MagnuM,™ and Saber Extra,™ Double Barrel™VP) Macrocyclic Lactone (XP 820™).
Recent studies in Nebraska (Fig. 1 below) illustrate the performance of selected ear tags against horn fly populations. Ear tag efficacy declined over time but the point where the economic threshold was exceeded varied among the products tested.
Figure 1. Representative results of ear tag control of horn flies in west central Nebraska. 2011 study.
To achieve the maximum performance from an insecticide ear tag, two tags per animal are required, and delaying ear tagging until June 1st will provide a producer with the greatest degree of horn fly control. A livestock producer in Nebraska can expect 12 to 14 weeks of horn fly control if the aforementioned methods are utilized.
The face fly, Musca autumnalis (DeGeer), is a robust fly that superficially resembles the house fly. It is a nonbiting fly that feeds on animal secretions, nectar, and dung liquids. Adult female face flies typically cluster around the animals' eyes, mouth, and muzzle, causing extreme annoyance. They are also facultative blood feeders, meaning that they gather around wounds caused by mechanical damage or other injury to feed on blood and other exudates. Because face flies are on animals for only short time periods they are difficult to control. Most of the time they are found resting on plants, fence posts and other objects.
In addition to being very annoying to cattle, face flies vector Moraxella bovis, the principal causal agent of bovine pinkeye or infectious bovine keratoconjunctivitis. Pinkeye is a highly contagious inflammation of the cornea and conjunctiva of cattle. If coupled with the infectious bovine rhinotracheitis (IBR) virus, M. bovis can cause a much more severe inflammatory condition.