Page 15 - MWC 08-5-2021s
P. 15

The Midwest Cattleman · August 5, 2021 · P15
                                                        Fly Control Considerations for Cattle on Pasture

                                                                      By Adele Harty, SDSU Extension Cow/Calf Field Specialist and Patrick Wagner

                                                         ly results in  than $1 billion annually in  between 30 and 40 blood
                                                         high numbers.  the United States. This loss  meals per day. After mating,
                                                         It is import- is a result of skin irrita- the  adult females deposit
                                                         ant to identify  tion, blood loss, decreased  eggs in fresh manure and the
                                                         (Figure 1) and  grazing efficiency, reduced  eggs typically hatch within
                                                         understand  weight gains, and decreased  one week. The total life cycle
                                                         life cycles of  milk production. Research  of the horn fly is between 10
                                                         external pests  in Nebraska found that calf  and 20 days, depending on
                                                         affecting  live- weaning weights were 10–20  weather conditions.
                                                         stock in order  pounds (lbs.) heavier when           MANAGEMENT
                                                         to choose the  flies were controlled on the             The economic injury level
                                                         most effective  cows.                                (EIL) for horn flies is 200 flies
                                                         control      op-     Horn flies are about 1/2 to     per animal. At this point, the
                                                         tions.             1/3 the size of the common        economic impact of the pest
         Along with being irritants      Horn Flies                         house fly, or approximate-        equals  treatment  costs, and
      to livestock, horn flies, face        Horn flies are one of the       ly 3/16 of an inch long. They     a treatment plan should be
      flies and stable flies are eco-    most common and economi-           are commonly found on the         started. Multiple insecticide
      nomically  important  to  pro-     cally important ectoparasites      backs, sides, and polls of cat-   options are available to man-
      ducers due to their negative       of pastured cattle. Economic       tle. During the heat of the       age horn flies, including dust
      impacts on milk production         losses are estimated at more       day, horn  flies will migrate     bags, backrubbers (oilers),
      and calf weaning weights. In                                          to the belly.  As adults, they    feed additives, sprays, pour-
      addition, they can affect graz-                                                      spend most of      ons and insecticidal ear tags.
      ing distribution and transmit                                                        their time on         Dust bags or oilers may be
      eye diseases, such as pinkeye                                                        cattle,    pierc-  either forced use (placed in
      and infectious bovine rhino-                                                         ing the skin of    an area that animals must
      tracheitis (IBR). It is difficult                                                    host    animals    pass through) or free choice.
      to predict what fly levels will                                                      to suck blood.     However, if they are not in a
      be like for any given year, but                                                      Both male and      forced use area, expect 35–
      hot, dry weather can speed                                                           female      horn
      up development and usual- Figure 1. (From Left) House fly, stable fly, horn fly and face fly.  flies may take        continued on page 19

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