Journal of the NACAA
ISSN 2158-9429
Volume 6, Issue 2 - December, 2013


Capture and Control of an Old West Desperado: Broom Snakeweed

Keyes, J.D., Area Range and Animal Scientist, Utah State University
Banks. J, Extension Agent, Utah State University
Ralphs, M, Research Rangeland Management Specialist, USDA-Agricultural Research Service, Poisonous Plant Laboratory
Ransom, C, Associate Professor, Plants, Soils, and Climate Dept., Utah State University


Broom snakeweed (Gutierrezia sarothrae [Pursh] Britt. & Rusby) is a native invasive species that prospers on arid rangelands following disturbance.  A study was initiated to evaluate the effectiveness of potential herbicides to control broom snakeweed growing on a blue grama site in the Colorado Plateau and the sagebrush steppe in the Great Basin.  Herbicide treatments were applied in a randomized block design and  replicated in 4 blocks at both locations. The herbicides Tordon 22k Grazon P+D, Escort XP, Telar XP, Milestone, and Clarity were applied at the high and mid-point recommended rates. Spring and fall applications were made to evaluate seasonal differences.   Broom snakeweed density and associated plant cover were evaluated on each site prior to herbicide treatment in June 2008 and one year after treatment at peak standing crop (June 2009).  Tordon 22K (0.28 or 0.56 kg/ha) was most effective when applied either spring or fall. Grazon (1.42 kg/ha) and Milestone (0.12 kg/ha) were most effective when applied in fall   Perennial grass cover increased with increasing efficacy of the herbicides.  Grass cover on Tordon plots was 2.5 fold greater than the untreated check.


Broom snakeweed has been considered a desperado of plant species for numerous decades.  The poisonous property of perennial snakeweed was documented as early as 1936.  Researchers found that ingestion could cause death in ruminants.  Sometime later, after years of incrimination by ranchers, studies verified that snakeweed can also cause abortion in ruminants. Snakeweed poisoning can be the source of retained placentas, pre-mature calves that are weak and underweight, and other reproductive disorders ( Carpenter, Ethridge, and Sosebee, 1990).


Broom snakeweed (Gutierrezia sarothrae (Pursh)Britt. & Rusby) is an undesirable perennial half-shrub found on much of the rangeland in the western half of the United States and northern areas of Mexico.  Often called matchbrush, broomweed, brownweed, yellow-top, torchweed or turpentine-weed, it is a serious problem throughout the arid ranges of North America.  Ranchers and land managers have long struggled with adverse snakeweed communities.

Snakeweed has unbranched woody stems that grow upward from a basal crown giving it a broom shaped appearance. These stems die back each winter, and new growth starts from the crown in early spring. Once established, snakeweed typically survives 4 to 7 years (Dittberner, 1971). Each plant can produce 2036 to 3928 seeds/plant Seeds held in dried flower heads are gradually dispersed over winter. Seeds generally drop close to the parent plant because they have no specialized structures such as wings to aid in long range dispersal.  Seeds remain viable into spring, but rapidly disintegrate after May if they remain exposed on the soil surface (Wood, McDaniel, and Clason,1997).


The production and economic losses caused by snakeweed infestations stem from the adverse effects on two complementary processes. The forage yield is reduced on infested areas and livestock production efficiency is impaired when the plant is consumed (Carpenter et al., 1990).

Snakeweed often can become a totally dominant species following some type of disturbance to the range such as fire, overgrazing, or drought (McDaniel and Torrell, 1987).  When snakeweed is controlled, grass production increases.  Typically, grass yield increases 4 to 6 fold after a dense snakeweed stand dies-out or when the weed is removed by herbicide spraying (McDaniel, Pieper, and Donart, 1982).

Consumption can cause abortions in livestock if eaten at a certain stage of pregnancy (Dollahite and Anthony, 1957).  Abortion happens when snakeweed is grazed during the last trimester of gestation (James, Panter, and Nielsen, 1992). In general, snakeweed poisoning has a substantial economic impact on animal efficiency when cattle are grazing pastures with moderate to heavy infestations.  The revenue per cow producing unit received from snakeweed infested pastures is 22% less with a moderate infestation and 45 percent less with a heavy infestation (Carpenter, Ethridge, and Sosebee, 1991).


Improvements in herbicide efficacy and treatment recommendations have made it possible to economically control problem stands of snakeweed (Carpenter et al., 1991).  Although there has been extensive research on the control and eradication of this plant, as new products are developed investigations need to be made to keep ranchers and land managers aware of what is most effective.  New rangeland herbicides are currently available. 

The objective of this study was to compare some of the new rangeland herbicides with picloram and metsulfuron.  We wanted to look at season of application and measure the response of desirable species.  The desired result was to find an efficient and economical way of controlling snakeweed infestations for ranchers and land managers.

Our Study Areas

We chose two sites, one on the Colorado Plateau and another in the Great Basin.  The first site is located 36 km north of Monticello, UT (N 28 13’ 06.99”, W 109 25’ 05.49”).  The plant community consists of Blue grama (Bouteloua gracilis (H.B.K.) Lag. ex Griffiths), Needle and thread (Stipa comata Trin. & Rupr), Indian ricegrass (Stipa hymenoidesR. & S.), Mormon Tea (Ephedra viridisCoville), Four wing salt bush (Atriplex canescens(Pursh) Nutt.), and Big basin sagebrush (ArtemisiatridentataNutt. ssp. tridentata).  The site has been used exclusively for grazing, and suffered extreme drought in 1996.  The density of mature snakeweed plants at the beginning of the study in 2008 was 15 plants/m2.

The second site is located 12 km west of Nephi UT (N 39˚ 43’ 44.702”, W 111˚ 53’ 28.891”).  The original plant community was Wyoming big sagebrush (Artemisia tridentata var. wyomingensis (Beetle & A. Young) Welsh) and Indian ricegrass (Stipa hymenoides R. & S.).  A wildfire burned the site in July 1998 and it was seeded the following winter to crested wheatgrass (Agropyron cristatum L.).  Snakeweed reinvaded the site and its density averaged 2.1 plants·m-2 in 2002.  A new crop of snakeweed seedlings established during the wet year of 2005, and the density of mature snakeweed plants at the beginning of the study in 2008 was 19 plants / m2.

Experimental Design

The experimental design was a completely randomized block design.  There were 6 commercial herbicides used in the project.  They were Clarity, Telar, Escort, Milestone, Grazon, and Tordon. The herbicides were selected as to their potential for controlling invasive shrubs.  Each herbicide was applied at two different rates plus an untreated control segment for a total of 13 treatments (Table 1).  The treatments were applied in the spring (June) and fall (August) 2008 using a back pack sprayer.  Plot size was 3 x 10 m.  Treatments and seasons were replicated in four blocks at the two locations.         

Density of snakeweed plants was counted along 1 x 10 m belt transects running down the center of the plots.  Foliar cover was determined by the line intercept method for snakeweed, perennial grasses, annual grass, forbs and shrubs.  Density and cover measurements were taken before treatment in June 2008, and one year after treatment at peak standing crop (23 June 2009).

Table 1. Herbicide Treatment Rates
Herbicide Trade Name Rate Rate
    Product/acre ae/ai
Dicamba Clarity 16 fl oz .56
    32 1.12
Chlorsulfuron Telar 0.5 oz .046
    1.0 .092
Metsulfuron Escort 0.5 oz .058
    1.0 .115
Aminopyralid Milestone 5 fl oz .087
    7 .123
Picloram + 2,4-D Grazon 2 pt 0.71
    4 pt 1.42
Untreated check      

*percent acid equivalent/active ingredient

Snakeweed Control

Colorado Plateau

At the Colorado Plateau site, initial density of snakeweed in 2008 was 15.1 plants/m2 and its foliar cover was 19%.  Total herbaceous cover was 25%.  There was an area wide die off of snakeweed in 2009.  As a short-lived perennial that propagates by seed, snakeweed needs optimal environmental conditions and will die out from drought stress or insect damage (Ralphs and Sanders, 2002).

Snakeweed density in the untreated check plot declined to 2.5% (Table 2), and all snakeweed plants in the treated plots were killed.  Perennial grass cover averaged 4% prior to treatment in 2008.  It increased to 10% in 2009 in the spring treatments, but only 8% in the fall treatments (Table 3).  Reduction in snakeweed competition for the remainder of the 2008 growing season benefitted the grasses in the spring treatments.

Great Basin

At the site in the Great Basin initial density of snakeweed in 2008 was 19 plants/m2 and its cover was 16%.  Total herbaceous cover was 23%.  In 2009, density of snakeweed in the untreated check plot was 14.16 plants / m2.  Averaged over rates and seasons, tordon killed more snakeweed plants that any other treatment (Table 2).  The high rate of Tordon (0.56 kg/ha) gave near total control in both seasons.  Milestone was effective when applied in the fall, and the high rate (0.12 kg/ha) gave 90% control.  Escort was more effective in the fall and its high rate (0.115 kg/ha) gave 83% control.  Telar and Clarity were ineffective.

Table 2. Snakeweed density and control one year after treatment.

Herbicide Rate Rate Density   Herbicide Control %  
  Product/acre ae/ai Spring n/m2 Fall n/m2 Mean n/m2 Spring Fall
Check     13.67 14.65 14.16a    
Clarity 16 fl oz .56 17.25 16.43 13.97a 0 0
  32 fl oz 1.12 11.10 11.10   19 24
Telar 0.5 oz .046 14.44 17.50 14.31a 0 0
  1.0 .092 11.59 13.70   15 7
Escort 0.5 oz .058 11.02 s 5.60* 7.84bc 19 62
  1.0 .115 12.17 s 2.57*   9 83
Milestone 5 fl oz .087 12.0 s 5.30* 6.58c 12 64
  7 .123 7.93* s 1.07*   42 93
Grazon 2 pt 0.71 12.44 17.31 8.69b 9 0
  4 pt 1.42 3.55* s 1.45*   75 90
Tordon 1 pt .28 6.42* 4.10* 2.71d 54 72
  2 pt .56 0.25* 0.08*   98 99
Check     3.2 1.8 2.5    
All Herbicides     0 0 0    
 abcd Difference between herbicides averaged over season and rate (P < 0.05)
 * Difference between individual treatments and untreated check (paired comparisons P < 0.05)
 s Difference between season of application for individual treatments (P < 0.05)


Table 3.  Foliar cover of perennial grasses and snakeweed prior to treatment in 2008 and one year after treatment in 2009.

Herbicide Rate Rate Perennial Grass   Herbicide Snakeweed   Herbicide
  Product ae/ai Spring Fall Mean Spring Fall Mean
2008     6 5   18 15  
Check     8 8 8a 34 33 34a
Clarity 16 fl oz .53 10 11 11b 32 22* 21b
  32 1012 13 11        
Telar 0.5 oz .046 13 11 13b 36 36 30a
  1.0 .092 13 16*   21* 25*  
Escort 0.5 oz 0.58 14 12 14bc 24* 11* 15b
  1.0 .115 15* 11   25* 3*  
Milestone 5 fl oz .087 10 10 13b 11* 3* 7cd
  7 .123 15* 14   8* 0*  
Grazon 2 pt 0.71 13 17* 17cd 21* 11* 9c
  4 1042 22* 17*   5* 1*  
Tordon 1 pt 028 21 19* 19d 12* 3* 3d
  2 056 23* 19*   0* 0*  
2008     4 4   19 19  
2009     10 8   0 0  
 -Statistical comparisons are for Nephi only.
  abcd Difference between herbicides averaged over season and rate (P < 0.05)
 * Difference between individual treatments and untreated check (paired comparisons P < 0.05

Management Implications

In the American Southwest, Broom snakeweed is an ever-increasing problem for range managers.  As efforts are made to increase plant variety for wildlife and livestock, as well as environmental health, snakeweed invades and quickly becomes a monoculture.  

Increasing the productivity of palatable range plants is the main benefit derived from broom snakeweed control (McDaniel, 1981).  Prior studies have suggested that for enhanced re-growth of perennial grasses it is necessary to attain nearly 100% control of snakeweed plants (McDaniel, Peiper, and Donart, 1982).

Data in this study shows that Tordon at a higher rate can achieve this control target.  Both spring and fall applications were successful.  Land managers are able to apply this pesticide at their convenience.  Fall applications of Milestone, Grazon, and Escort also showed possibilities of reaching the target control. 

Forage production increased several fold when snakeweed competition was eliminated.    Reduction in snakeweed competition for the remainder of the 2008 growing season benefitted the grasses in the spring treatments.  In fac the Monticello site had become barren of Broom snakeweed, and the grass species flourished.


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Dittberner, D.L. 1971. A demographic study of some semidesert grassland plants.  Masters thesis, Las Cruces New Mexico: New Mexico State Univ. 81 p.

Wood, B. L., K. C. McDaniel, and D. Clason.  1997. Broom snakeweed (Gutierrezia sarothrae) dispersal, viability, and germination.  Weed Sci. 45:77-84.

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