Using Fire to Manage Horn Flies on Cattle

Horn flies on a beef cow

Indigenous tribes of North America, Africa and Australia used fire for a variety of reasons including control of insects.  Commercial livestock operators have typically not recognized the impact of fire in reducing parasites on animals.  While the impact of fire on external parasites such as ticks has been documented, there has been little attention paid to how fire could be used to manage fly pests of cattle.  Horn flies are an external parasite of cattle that cause over $1 billion in economic losses each year.   Cattle serve as hosts for horn flies by providing blood meals and fecal pats that are used for laying eggs and overwintering pupa.  Given the fire prone ecosystems of North America, range scientists and livestock entomologists are evaluating the response of horn flies (a non-native pest from Eurasia) to fires.  The current trend in managing horn flies is with insecticides that are fed, sprayed or impregnated in ear tags.  Resistance to chemical active ingredients is a major problem and is now widespread.

Recent Findings

In 2011, cattle in Oklahoma and Iowa were evaluated for horn fly numbers.  Cattle were either on pastures that were patch-burned (a portion of the pasture burned each year) or on pastures that had not been burned in over two years.  All fires were conducted in March of that year.  Horn flies were counted during periods of peak activity and data was evaluated for location and treatment effects.  Cattle on pastures that were patch-burned had 41% fewer horn flies than cattle on pastures that had not been burned.  The accepted economic threshold for treatment of horns flies is 200 flies per cow, with 300 flies per cow causing behavioral stress. The unburned pastures had >400 horn flies per cow, while the patch burn pasture cows had approximately half as many horn flies.  It is thought that the application of fire is effective by two primary mechanisms: (1) cattle spend more time in the recently burned patch than unburned patches (as they are attracted to the highly palatable and nutritious plant regrowth after fire) and (2) fire in the dormant season (late winter and early spring) alters cow pats when pupa are overwintering in or below them.

Benefits of Fire Relative to Parasites

Using fire to manage horn flies is anticipated to have a number of positive impacts, including:  (1) reducing horn fly numbers is expected to result in a reduction of stress annoyance behaviors such as twitching, head throwing and swishing of the tail and ultimately an increase in grazing time, (2) reducing horn flies has been documented in numerous studies to have a positive impact on cattle performance, (3) the potential impact of fire on any parasite of cattle is an exciting alternative to the use of pesticides and a potential strategy to avoid the development of resistance to chemical treatments, (4) fly pests of cattle have been documented to vector diseases (horn flies are suspected of transmitting anaplasmosis and face flies are suspected of transmitting pinkeye).  Lastly, fire provides other benefits to pasture such as slowing woody plant encroachment and removing dormant plant litter and allowing for lush regrowth of grass. 

Using Prescribed Fire to Control Ticks

Prescribed Fire

Prescribed Fire

Troublesome pests such as ticks can be controlled with fire. However, for most parasites, control by fire lasts only for one growing season post-burn.

Economic Loss

Many tourism areas suffer economic loss because of the public’s perception of ticks and other pests in parks, campgrounds, and other recreational facilities. Ticks pose a serious health risk to humans, pets, livestock, and wildlife because of the diseases they can carry. Rocky Mountain spotted fever, Lyme’s disease, and other infections can be transmitted to humans from ticks. Domestic animals can also contract fatal diseases from ticks. Decreased livestock production from insect borne illnesses can also cost livestock producers thousands of dollars each year.

Controlling Ticks With Patch-Burning

Current research suggests patch-burning (patch-burn grazing) significantly reduces ticks on domestic livestock. When a patch is burned, the livestock follow the fresh burned areas and camp out on those areas until another patch is burned. Burning the patch kills the ticks, removes their habitat, and limits the livestock’s contact with ticks because they are concentrated on the burned area. Since the livestock follow the burns, they remain in areas with fewer ticks.

Weather Conditions for Controlled Burns

Although controlled burns can be conducted under pre-determined weather conditions, burns can be unsafe if the experience of the burn boss and crew is inadequate.

People new to burning should consider using the 60:40 rule. The 60:40 rule refers to restricting burn conditions to air temperatures less than 60 degrees Fahrenheit and relative humidity (Rh) greater than 40% with a wind speeds of 5-15 mph measured at 6 feet above the surface of the ground.

Rule of Halves

The rule of halves is an easy way to remember how to predict changes in fire behavior when the weather changes. When the air temperature increases by 20 degrees Fahrenheit, the relative humidity decreases by 50%. For example, if the air temperature changes from 60 degrees Fahrenheit with 40% relative humidity to 80 degrees Fahrenheit, the relative humidity will change from 40% to 20%, making the spotfire risk increase dramatically. In most cases, do not burn if there is a forecasted frontal passage or wind shift within 12 hours.

Weather Tools

There are many weather tools available. Make sure and check the wind direction, speed, temperature and relative humidity a few days before the burn, and right before the burn. It is very helpful to take notes of weather conditions during the burn. This can help people learn how to predict fire behavior in the future. On-site weather meters can be very helpful in taking up-to-date weather.

If conditions are not correct, including all parts of the prescription, do not start the fire. If the fire is not going well, put it out. Do not leave the fire until it is completely out, which means no smoke detected for at least one hour.

View this fact sheet for more detailed weather information regarding spotfires: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2704/NREM-2878web.pdf

Types of Fire

There are many different techniques that can be used when lighting prescribed fires. The types of fire produced depend upon ignition technique and direction of the wind. These different types of fire are used in different areas of the burn depending on the conditions and objectives. The different types of fire include backfire, flank fire and head fire.

This image depicts the parts of a fire.

Types of Fire

A backfire is when you light off of a fire line and the flames burn into (against) the wind. Backfires are frequently used to create a line of “black,” or burned fuel, on the downwind side of the burn unit prior to lighting the flank or head fire. Backfires burn slowly and typically have short flame lengths.

A flank fire is a fire that burns perpendicular to the wind direction. Flank fires are commonly used after a backfire has been lit and let burn a safe distance, and prior to ignition of the head fire. Flank fires burn more quickly than backfires and the flames are greater in length.   

A head fire is created when the fire burns with the wind, pushing the fire towards the un-burned fuel. Head fires are used when there has already been a backfire lit on the downwind side of the burn, and flank fires lit, or if you are burning towards an area such as a large body of water, or previously burned unit with no remaining fuel. Head fires move quickly and typically have longer flame lengths than the other types and can produce intense heat.

Ignition Techniques

A strip backfire is when you light multiple lines of backfires, usually just 5-15 yards apart. This is commonly used to speed up the process of putting in “black” or burned area prior to flank or head fires.

Strip flank fires are less common, because they can turn into a “running flank fire” if the wind direction changes, and can be dangerous for the burn crew. If this technique is used, the people igniting should be alert and aware of any wind shifts.

Ringing a burn unit, is when the perimeter of the entire burn unit is lit off at once. Ringing a burn unit is not as common as other ignition techniques, and is usually only done in a small burn unit. This is a very quick method of burning because the flames from each side of the burn unit feed off of each other and suck together, but if the wind switches it can easily cause an escape. This should only be done by very experienced burn bosses and crews.

The most common process of lighting a prescribed fire begins when the backfire is lit off of the downwind fire line. Once there is a safe amount of black, a person on each side of the unit will uniformely ignite the flank fires. When they reach the respective head fire area of the unit, they pause to monitor the amount of fuel that the back and flank fires have burned. When there is a sufficient amount of “black” or burned area, the two will wither ignite the headfire from both corners and meet in the middle, or one person will ignite the head fire.

Every burn plan and ignition type is different. Use what works best for the burn unit, crew and available equipment.

Controlling Eastern Redcedar with Prescribed Fire

 

The use of fire has decreased since European settlement due to fragmented landscapes caused by farming and over-use by livestock. This has resulted in a rapid change of landscapes, from open prairies or savannahs to closed canopy forests, and in many cases monocultures of eastern redcedar trees.

Fire Suppression

In prairies and shrublands, fire suppression resulted in an increase in both fire-tolerant woody plants that resprout, and fire-intolerant woody plants such as eastern redcedar and ashe juniper.

Fire suppression has resulted in a decline of habitat specialist wildlife species including the Northern bobwhite, lesser and greater prairie chickens and many songbirds. Fire is also very important for other wildlife species such as wild turkeys, white-tailed deer, and elk.

Restoring and Maintaining Landscapes with Prescribed Fire

Prescribed Fire

Lighting head fire during a controlled burn.

The most economically and ecologically sound tool to restore and maintain native landscapes is prescribed fire. The regular use of fire prevents invasion of eastern recedar into prairies, shrublands, and forests. Fire can also control resprouting woody plants when the frequency is at least every three years. Fire is an ecosystem driver that facilitates ecosystem processes, including nutrient cycling, water cycling, and soil health. Fire helps maintain watershed function, water quality, and water yield. In some cases, fire has been excluded for so long, that mechanical and/or chemical tools need to be used in the restoration process.

Mechanical Treatments

Eastern redcedar trees cut with a tree cutting attachment on a skid steer.

There are many types of mechanical treatments that will control eastern redcedar from hand tools to heavy equipment. However, mechanical treatments are very costly when compared to fire, and they do not offer the same ecosystem benefits. If fire is not part of the management plan, mechanical treatments have to be repeated very frequently, which can be very labor intensive and costly.

Small eastern redcedar infestations can be controlled by using hand-held shear/loppers, chainsaws, or brush cutters. These treatments need to be repeated at least every three years as new eastern redcedars will continue to rapidly invade.

Proper Grazing Management

Proper grazing management is mandatory to ensure that enough fine fuel is available to carry a fire and burn eastern redcedars. If eastern redcedar trees are not controlled, stocking rates need to be reduced frequently to account for the loss of grass. Eventually the eastern redcedar will become so thick that fire will not carry across the area, except under extreme wildfire conditions.

Heavy Infestations of Eastern Redcedar

Heavy infestations by eastern recedar are very expensive to control and require heavy equipment. Hydraulic saws and clippers will produce the best results, but can be time consuming unless it is hired out by a company or most of the managers time is spent cutting. Bulldozers can be very costly and cause soil disturbance, and are not recommended unless in extreme conditions. These treatments need to be followed by fire or the manager will be in the same situation.

The use of prescribed fire is the most recommended tool for eliminating eastern redcedar. A land management plan should exist on every piece of property to ensure the land is functioning at its highest potential.

Do I need a permit to conduct a prescribed fire?

Requirements and permits necessary to conduct prescribed fires vary from state to state. For example, some states require a permit, while others simply require notifying the fire department nearest to the burn site. Contact your local county extension agent, Natural Resource Conservation Service Center, or fire department for details about permits in your area. If applicable, check with your state prescribed fire council for additional guidance (Coalition of Prescribed Fire Councils).

Setting Prescribed Fire Objectives

Prescribed fire is an effective tool for managing vegetation.  Prescribed fire can be used to improve forage for livestock and wildlife, control both non-native and native invasive species, remove leaf litter, reduce logging debris, improve tree regeneration, and manage vegetation competion. Fire is an excellent tool for vegetation management, but prescribed fires need to be planned to consistently achieve the beneficial effects. 

 

A successful prescribed fire program involves three steps:

1) planning-including evaluating the condition of vegetation and vegetation management goals

2) safe and effective prescribed fire execution

3) sound vegetation management pre-, during, and post-prescribed fire treatment. A prescribed fire plan is an essential part of the process for preparing to use prescribed fire. 

The prescribed fire plan includes prescribed fire objectives, weather conditions, plans for fire control, identification of authorities to notify prior to prescribed fire ignition, prescribed fire ignition plans, and post-prescribed fire plans. Below are links to sites with information on prescribed fire planning:  Michigan Department of Natural Resources, Florida Forest Service, U.S. Forest Service Southern Research Station, Georgia Forestry Commission, New Hampshire Prescribed Fire Council, and Oklahoma State University.     

Determining Land Management Objectives

Planning to use prescribed fire starts with determining what the land management objectives are and deciding if prescribed fire will help achieve the objectives.  This process can take some time, but it is very important for determining where, when, and how prescribed fire can be used.  Once it is determined that prescribed fire is an appropriate tool to meet the objectives, then a prescribed fire plan should be prepared.  The prescribed fire plan is a document that describes the area to be treated with fire, the prescribed fire objectives, and a plan that includes a combination of prescribed fire ignition techniques, season of burn, and weather conditions to meet the defined objectives.  Setting the objectives of the prescribed fire is a very important step in prescribed fire use.

Prescribed fire objectives need to provide enough detail that the prescribed fire can be evaluated to determine if it was successful.  Objectives can be both short- and long-term.  Short-term objectives should be quantifiable. 

Short-Term Objectives

  • Reduce leaf litter by 70%
  • Reduce understory shrubs by 50%
  • Consume 60% of tree branches less than 1inch in diameter from logging debris.
  • Consume 90% of fine fuels.
  • Increase grass cover by 20%
  • Increase native plant species richness by 5 species.

Long-Term Objectives

Long-term objectives can include the desired future conditions that the landowner is trying to achieve by using prescribed fire.  Examples of long-term objectives are:

  • Promote native grasses.
  • Reduce the cover of exotic species
  • Restore woodland structure
  • Convert site from hardwoods to softwoods
  • Improve forage for livestock

     

       

Additional Literature:    

Fire in southern forests: http://www.treesearch.fs.fed.us/pubs/6462

Fire in Ponderosa Pine Forests in the Pacific Northwest: http://www.treesearch.fs.fed.us/pubs/21805

Prescribed fire effects literature review and synthesis: http://www.treesearch.fs.fed.us/pubs/33628

Individual Cedar Control with Fire

Prescribed fire is the most economical method to control ash juniper and eastern redcedar in the Great Plains. But many times these trees are too large by the time land managers use fire to control them. In this case, the lower leaves will turn brown and eventually fall off with the remaining upper portion of the tree staying green and living. Shortly after a prescribed fire is conducted, when the lower leaves of these juniper trees become brown, is a good time to conduct individual tree ignition.

Individual scorched-tree ignition is a very economical follow-up to prescribed burning and can be done over a period of several weeks. Ignition of these trees can be accomplished with a propane weed burner torch, drip torch, hand held propane or MAP gas torch. It is best to do individual tree ignition when the wind is very light or calm so the heat and flames can draw straight up into the crown of the tree, killing the entire tree.

Remember to have fire fighting equipment on stand by in case embers from crowning trees drift into unburned areas. Also be sure to notify the local authorities and neighbors before re-burning trees.  The the smoke and flames that this technique creates from crowning trees will be visible to neighbors.  Always be sure to follow all local and state laws regarding the use of fire.

To watch a short video about individual tree cedar control using fire, go to the following video link: http://www.youtube.com/watch?v=am6yXl-paQ8&feature=player_detailpage 

For more information about individual tree cedar control using fire, see the Oklahoma State University Extension fact sheet NREM-5053 Cedar Control by Individual Scorched-tree Ignition Following Fire http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-7936/NREM-5053.pdf 

 

 

 

With proper conditions you can ignite a single point on smaller trees or several point on larger trees along the browned lower branches on the upwind side.

 

Re-igniting unburned cedars following a prescribed fire is a safe, effective and very economical method of controlling larger cedars.

Managing Shrubs in the Southern Great Plains with Prescribed Fire

The southern Great Plains includes portions of Kansas, Oklahoma, Texas, New Mexico, and Colorado.  This area is semi-arid grassland that is characterized by a highly variable climate.  Within portions of this grassland, resprouting shrubs dominate on certain soil types.  This is particularly true for sand sagebrush and shinnery oak which occur on deep sands.  Other subdominant shrubs in this region include various species of plum and sumac.  These shrubs provide various ecological services.  Many species of wildlife rely on them for protective cover, thermal cover, and nesting cover, as well as for food resources.  Northern bobwhite, Bell’s vireo, lesser prairie-chicken, and Cassin’s sparrow in particular are associated with shrubs in this region.  Additionally, these shrub species are deep rooted and help stabilize soils from wind erosion from fires, as well as during the frequent droughts that characterize the variable climate of the Great Plains.

Direct Impacts to Shrubs

Often, managers wish to know how prescribed fire will affect shrubs.  As with all grasslands, the southern Great Plains ecosystem evolved with fire.  Thus, it is not surprising that the vast majority of shrub species within this region resprout from the root following a disturbance such as fire. Thus, fire will rarely result in mortality to the plant. However, fire does result in a temporary change in plant composition and structure.  Following fire, many shrubs will be top killed.  In other words, the above ground portion of the plant is consumed by the fire.  The degree to which this occurs will depend on the fuel load, relative humidity, and other factors.  Depending on rainfall following the fire, annual forbs (broad leaved herbaceous plants) and grasses tend to increase for the first 2 to 3 years following fire.  In shrub dominated areas (sand sagebrush and shinnery oak), this impact is short-lived as the shrubs rapidly resprout and again dominate the site. Over time, the shrub stems will gain height and within 3 to 4 years sand sagebrush and shinnery oak will return to pre-burn conditions.  Species such as sand plum  will also resprout, but grow slower.  This clonal shrub species grows in dense “mottes” where many stems are part of the same individual plant.  The edge of the motte is often top killed by fire; while the interior remains unscathed (This will vary with fuel and conditions during the burn).  Research has shown that sand plum mottes will increase in area over 330 square feet per year.  Thus, depending on the original size of the motte, it may take several years following fire for this shrub to return to pre-burn conditions.

Associated Impacts

The change in plant composition and structure has dramatic impacts to wildlife species and also to livestock production. Wildlife species that require shrubs may be temporarily displaced until the shrubs dominate the site once again.  Alternatively, other species which require higher amounts of grass and forb cover will increase on these burned areas for the first few years following a fire.  The increase in grass production and crude protein of grass associated with prescribed fire will be attractive for livestock for 2 to 3 years following the fire.  Thus, periodic burning in these shrub communities can be a valuable tool to increase livestock performance.  However, due to the variable climate patterns, burning only a portion of a pasture in any one year is a good hedge against droughts.  Some producers wish to use herbicides to eliminate shrubs in favor of grass to increase livestock performance. First there is no economic benefit to this or should increase in livestock production. It is also a risky practice in an area known for highly erodible soils.  Thus, to maintain adequate root biomass for soil stability, and to ensure shrub obligate wildlife has adequate habitat, the use of periodic prescribed fire over portions of a pasture can be used by livestock producers.    

Sand plum is a clonal shrub, where many individual stems are part of the same plant. This plant grows in dense “mottes” as seen in this photo. Fire often top-kills some of the stems along the periphery of the motte. However, large mottes generally are not completely top-killed but rather reduced in size by fire. Over time, this motte will expand by vigorous root sprouting stems.

This sand sagebrush plant community was burned 5 months prior to this photo. Notice the sand sagebrush resprouts across the pasture.

Shinnery oak is another clonal shrub that can have thousands of stems per acre. This photo depicts a recent prescribed fire (right portion of photo) and an unburned area (left portion of photo). Notice that the recently burned area is grass dominated. This is a temporary condition as shinnery will return to pre-burn conditions within 3 to 4 years post fire.