Managing horn flies on cattle with patchy fire

Horn fly load on a beef cow in unburned prairie

Horn fly load on a beef cow in unburned prairie

Range scientists at Oklahoma State University are bringing back to life an old concept: livestock pest management with fire.  Indigenous tribes in North America, Africa and Australia are known to have used fire to manage insects including ticks and flies.  Researchers have documented the impact on ticks, but other parasites, specifically horn flies (Haematobia irritans L.), plague cattle grazing on rangeland.     

Horn flies are not native to North America, and they rely on cattle for blood meals and feces for egg laying resources.  In the Great Plains, horn flies overwinter as a puparium in or directly beneath cattle fecal pats.  Economic losses from this parasite are estimated to exceed $1 billion annually in the United States (adjusted for inflation).  Control can be difficult as horn flies can quickly develop resistance to active ingredients of chemicals.

A study in Oklahoma and Iowa is underway to assess how fire might influences horn fly numbers.  In 2011, horn flies were counted on cattle in pastures managed with patch-burning and compared to cattle on pastures that had not been burned in more than two years.  Results indicate that patch-burning resulted in a 41% reduction of horn flies during periods of peak horn fly activity (Scasta et al. 2012).  These results were significant regardless of location.  

Oklahoma State University burn crew

Oklahoma State University burn crew

We hypothesize that the treatment effect is the result of cattle spending more time in recently burned patches than unburned patches, and that fire in the dormant season (particularly late winter/early spring) alters cow pats (which are overwintering locations for horn flies).  

Reducing horn flies is anticipated to have a number of impacts on cattle production, including: (i) decreased stress annoyance behaviors (head throwing, tail flicking, twitching, etc) and longer grazing time; (ii) increased weight gain; (iii) reduced reliance on chemical treatments and potential resistance of horn flies.  In 2012, we have expanded our sampling to include other species of flies, we will look at season-long impacts, and we will compare patch-burning to burning the entire pasture.  It is also important to consider that flies can serve as vectors for  viral, bacterial and parasitic diseases (such as pinkeye and face flies).

This project is part of a larger goal of understanding the potential benefits of fire and patch-burn grazing to rangeland grazing operations in the Great Plains.  The implications of integrating fire into the ranch operation are far reaching and the potential to mitigate parasites may have been an unrecognized benefit in the past.  Oklahoma State University recently profiled this research in its SUNUP TV program.

Scasta, J.D., Engle, D.M., Talley, J.L., Weir, J.R., Stansberry, J.C., Fuhlendorf, S.D., and R.N. Harr. 2012. Pyric-herbivory to manage horn flies (Diptera: Muscidae) on cattle. Southwestern Entomologist. 37: 325-334.