Greenwood County reminds me of Ireland this time of year. The grass has had a chance to come back from the last few weeks of spring burns, and it is ready to have yearlings or cows turned out on it. With good spring rains and mild to warm temperatures, flies and other external parasites are things we must manage with our livestock now and through the summer.
It is estimated that horn flies alone may account for up to a billion dollars of damage and loss to the cattle industry each year. The horn fly is a blood feeding insect that inflicts a painful bite. Economic impact can be seen with as little as 200 flies per animal. This can be visualized by horn flies covering the withers and going about half way down the side of the animal.
It is recommended to use a multifaceted approach when controlling external parasites. In addition to burning, plan to use insecticides, fly tags, and feeding mineral containing an insect growth regulator, (IGR).
Common classes of insecticides include pyrethroids and organophosphates. Continued use of one class of product will promote resistance in the area fly population. Using one chemical class each season and rotating classes on a seasonal basis is critical to maintain the usefulness of these products. Timing is a critical component of insecticide use.
Consider putting in fly tags by mid to late May to maximize effectiveness. Many available tags may have an effective duration of 12-15 weeks. Use fly tags only once per season. Remove these tags at the end of the season to avoid continued exposure of these parasites to sub-therapeutic levels of the active chemical to reduce development of resistance.
An IGR works by either destroying developing larvae or disrupting the normal development process. The process reduces the amount of new fly activity in a given area. However, flies do have the ability to travel over distances from neighboring operations, so overall elimination with these products is not practical.
External parasites are annoying to livestock and costly to animal performance. Timely management and appropriate use of insecticides will help minimize their impact. If you have questions regarding the control parasites, or other livestock related questions please contact your local KSU Ag and Natural Resources Extension Agent Clinton Laflin. Laflin can be reached via email at [email protected], or by phone at 620-5837455.
