J. Range Manage. 55: 277-284 May 2002 Snakeweed: Poisonous properties, livestock losses, and management considerations

KIRK C. McDANIEL AND TIMOTHY T. ROSS

Authors are Professors, Dept. of Animal and Range Sciences, New State Univ., Las Cruces, N.M. 88003.

Abstract Resumen

(broom, sarothrae (Pursh) Britt & Snakeweeds (broom, (Pursh) Britt & "Snakeweeds" Rusby) "Threadleaf" (G. microcephala (DC.) Gray) caen den- Rusby); and threadleaf, G. microcephala (DC.) Gray) fall into y de la categoria de las malezas toxicas que raramente causan that class of poisonous weeds that seldom cause direct livestock tro perdidas directas de ganado porque ellas no le gustan al ganado losses because they are highly unpalatable and animals rarely consumen grandes cantidades de mate- consume large quantities of material. However, when y raramente los animales de estas plantas. Sin embargo, cuando el snakeweed becomes dominant on and retards growth rial vegetal llega a ser dominante en el pastizal retarda el of desirable forage, then indirectly it becomes a serious hazard to "Snakeweed" y de especies deseables, entonces se convierte en un animal health. Confined and rangeland feeding trials conducted crecimiento serio peligro para la salud animal. Estudios de alimentacion en at State University with and have failed en pastizal realizados en la Universidad Estatal to elicit reproductive failure with elevated snakeweed dosages. confinamiento y Mexico con ovinos bovinos han fallado en lograr un was shown to impair certain reproductive functions de Nuevo y Snakeweed con dosis elevadas de "Snakeweed". such as pituitary responsiveness to luteinizing hormone, and fracaso reproductivo "Snakeweed" mostro deteriorar ciertas funciones reproductivas caused mild hepato-renal toxicity. Under rangeland conditions, la respuesta de la pituitaria a la hormona luteinizante livestock grazing in areas dominated by snakeweed reportedly tales como causo una toxicidad hepato-renal ligera. Bajo condiciones de have more serious problems, such as abortion. A commonality y el ganado apacentando en areas dominadas por between confined feeding trials and rangeland grazing trials is pastizal, tiene problemas mucho mas serios como abortos. that in the presence of snakeweed, animals typically display "Snakeweed" Algo comun entre los ensayos en confinamiento los de apacen- symptoms associated with a low-plane of nutrition such as lack of y snakeweed tamiento en pastizales es que en la presencia de "Snakeweed" los gain, emaciation, and occasional death. To reduce piano interven- animales tipicamente muestran sintomas asociados con un dominance and improve range condition, management de peso, or fire control may be necessary. nutricional bajo, tai como la falta de ganancia tions such as herbicide Para reducir la dominancia del the decision regarding snakeweed control is the demacracion y muerte ocasional. Complicating mejorar la condicion del pastizal, es necesario uncertainty about treatment life and whether this relatively "Snakeweed" y practicas de manejo tai como el use de herbicidas o short-lived perennial weed might be eliminated by natural caus- realizar fuego para controlar esta planta. Algo que complica la decision es. Knowing the snakeweed population pattern in a given area respecto al control del "Snakeweed" es la incertidumbre acerca greatly enhances management decisions. de la duracion del tratamiento y si esta especie perenne de vida relativamente corta pudiera ser eliminada por causas naturales. Conociendo el patron de la poblacion de "Snakeweed" de una Key Words: Poisonous plant, range weed, livestock grazing, area dada mejora grandemente las decisiones de manejo. broom snakeweed (Gutierrezia sarothrae (Pursh) Britt & Rusby), threadleaf snakeweed ( (DC.) Gray) mainly in the Chihuanhuan and Sonoran deserts of Mexico and Rusby) and Broom (Gutierrezia sarothrae (Pursh) Britt & the southwestern . threadleaf (G. microcephala (DC.) Gray) snakeweed are short- Snakeweeds contain a rich mixture of alkaloids, flavonoids, lived perennial shrubs within the family. Because they saponins, terpenes, and other compounds that are often causal ecological are similar in appearance and often occupy the same agents in various that poison rangeland livestock. These niches, they are commonly referred together in the literature as substances also render snakeweed highly unpalatable so that indige- simply, snakeweed (Sterling et al. 1999). Both species are when given a choice animals usually will not eat the foliage. Bite distributed from nous to with broom snakeweed into a snakeweed leaf and you'll quickly appreciate from the is found Mexico to southern Canada, while threadleaf snakeweed harsh burning taste why other common names, such as fireweed and turpentine weed are so appropriate. Snakeweeds are rarely NM This paper was supported by the New Mexico Agr. Exp. Sta., Las Cruces, eaten by any large wild or domestic animal (Smith et al. 1991) 88003 and was funded in part by a special grant for Broom Snakeweed Research. Author to whom correspondence should be addressed. Dept. of Animal and and with the exception of a few specialist foliage feeding insects, Range Sciences, New Mexico State University, Las Cruces, NM 88003. Phone: such as the red-kneed grasshopper (Hesperotettix viridis (505) 646-1191; Fax: (505) 646-5441; E-mail: [email protected]. [Thomas]) (Thompson et al. 1995, Foster et al. 1981, Richman Manuscript accepted 2 Sept. 01.

277 JOURNAL OF RANGE MANAGEMENT 55(3) May and Thompson 1995) snakeweeds are Livestock displaying symptoms from duce isocaloric and isonitrogenous diets. rarely damaged by grazing. snakeweed poisoning under rangeland con- Smith et al. (1991) examined the response Pieper (1989) reviewed literature report- ditions are likely to have a decreased nutri- of rats to increasing levels of snakeweed ing snakeweed in herbivore diets and ent status and body condition accelerated in the diet ranging from 0 to 25%. These found it usually absent but occasionally as by malnutrition. Healthy grazing animals authors found that pregnancy rates much as 3 to10% of grazed diets in cattle, are not likely to eat the plant unless other decreased when dietary snakeweed horses, sheep, , mule deer, jack rab- forage is extremely scarce (Mathews exceeded 12.5 %. They also reported that bits, and antelope. When snake- 1936). Thus intuitively, with reproductive functions were impaired weed is grazed by livestock it is most like- poor forage conditions (or range condition) before evidence of liver or kidney damage. ly because it is the predominant green are areas of concern but can be remedied in In the Smith et al. (1991) study, they plant among other dormant or scarce the short term with nutrient supplementa- found that after 35 days of snakeweed species. Cattle, sheep, and horses are tion (Strickland et al. 1998) and in the long feeding that rats exhibited evidence of reportedly killed by ingesting 10 to 20% term by increasing forage availability. liver and biliary toxicosis indicated by ele- of an animals body weight with snake- vated alkaline phosphates, gamma-glu- weed (Kingsbury 1964), but problems Toxicity Studies at New Mexico tamyltranspeptidase, and alanine amino- with reproduction and abortion are more State University (NMSU) from 1980 transferase. When pregnant rats were fed commonly reported (Dollahite and to 2000 snakeweed at levels above 10% in the diet, Anthony 1957, Smith and Flores- Several studies have confirmed snake- embryonic mortality and early fetal death Rodriguez 1989). weed toxicity under confined feeding con- was noted. Also, blood urea nitrogen and While snakeweed poisoning problems ditions but, to our knowledge, no research creatinine concentrations were elevated can not be discounted, the literature sug- has been able to demonstrate snakeweed suggesting some damage to the kidneys. In is gests that it the plants competitive poisoning under actual rangeland grazing the aforementioned experiments by Smith nature that causes major economic damage experiments. Beck et al. (1999) grazed et al. (1991), snakeweed was harvested by to livestock (5 producers. Under dense mature cows in various experiments on hand clipping the new growth portion to snakeweed stands losses diminished from rangelands dominated by snakeweed on 10 cm) of the plant during pre-bloom. forage and livestock production usually far the Chihuahuan Desert Rangeland Oetting et al. (1990) fed snakeweed to outweighs it's toxic properties. In this Research Center near Las Cruces, N.M. ewes at levels ranging from 0 to 25% of paper we discuss some recent findings from 1992 to 1998 and never witnessed diets. With alfalfa hay as the base feed from research pertaining to snakeweed animals eating the plant. Similarly, graz- mixed with 25% snakeweed, ewes easily toxicology and management. We have ing trials with goats in the same area from consumed the diet. Ewes fed 12.5 and placed special emphasis on research we 1989 to 1993 reported little use of snake- 25% snakeweed with alfalfa hay experi- have been involved in at New Mexico weed except when other herbage was enced longer estrous cycles and higher State University'. grazed out (Beck et al. 1996). According serum progesterone concentrations than to Beck et al. (1996), heavy stocking ewes fed less snakeweed. When the base Toxicity Problems for 5 summer seasons resulted in no graz- feed included blue grama hay mixed with Saponins have been identified as the pri- ing damage to snakeweed because the ani- snakeweed, the ewes were unwilling to eat mary toxic substance in snakeweed, but mals removed so little plant material. Cox diets containing more than 10% snake- the plant also contains numerous other (2000) examined cattle grazing paddocks weed. Ewes that ate the blue grama hay compounds (essential oils, mono- and with varying snakeweed densities on four base diet with 10% snakeweed experi- sesquiterpenes, flavonals, tannins, alka- New Mexico ranches and after conducting enced mild liver and kidney toxicosis and loids, etc.) that contribute to their toxicity. microhistological evaluations reported had significantly lower estrual activity than animals fed 0% snakeweed diets. Kingsburg (1964) summarized the poison- snakeweed present in only 1 of 337 fecal ing symptoms reported by various investi- samples analyzed. Cox also followed indi- Working with cannulated sheep, Edrington et al. (1991) compared diets gators (Mathews 1936, Dollahite and vidual animals placed in 1 ha sized pad- Anthony 1957, Dollahite and Allen 1959) docks with very high snakeweed densities with 0, 50 or 100% fresh snakeweed and concluded in acute cases death occurs, (between 33 to 70% vegetation composi- placed directly in the rumen. Blood sam- but the major threat from snakeweed con- tion) and through bite count observations ples taken on these animals showed that sumption is abortion. Other toxic effects noted that snakeweed was usually not the 50 and 100% snakeweed diets elevated include premature calves and decreased grazed but that certain animals ingested levels of gamma-glutamyltranspeptidase, feed intake and body weight gains. Losses between 0.4 to 6% of their diet. Cox did aspartate amino-transferase, and alkaline caused by abortion and birth related not observe any visible toxicity symptoms phosphates, and that unconjugated biliru- abnormalities in cattle, sheep, and goats from animals that ate the plant. bin increased in the serum. These symp- from snakeweed are poorly documented Most NMSU investigations studying toms indicate that hepato-toxicity was and sporadic (Norris and Valentine 1957, snakeweed poisoning effects on animals occurring with the ewes fed snakeweed. Martinez et al. 1993). have relied on findings from confined Also, rumen function was affected as indi- feeding trials (Table 1). Experiments usu- cated by a shift from high acetate to more This paper was compiled in part, for the sympo- ally have included field harvested snake- propionate production in the rumen. These sium: Do most livestock losses from poisonous plants weed that is dried and ground in the lab data agreed with a similar study reported result from `poor' management? This symposium was by Hall et al. (1991). held in conjunction and then added in graded dosages with with the Society for Range Williams et al. an Management meeting in Boise, Ida. 13-18 Feb. 2000. hay, alfalfa, corn or soybean meal to pro- (1993) conducted experiment using 56 beef heifers fed either

278 JOURNAL OF RANGE MANAGEMENT 55(3) May 2002 Table 1. Feeding studies investigating snakeweed toxicosis with various herbivores from 1986 to the present at New Mexico State University.

Species Diet and Purpose Findings

Rats 0, 12.5, 25% SW' SW ingestion impaired fertility et a1.1991 Ovulation and and reproduction in female rats. embryonation Higher embryonic death Lower ovulation Fewer offspring/litter

Rats 0, 5,10,15% SW Body wt. declined (+17, +16, et al. 1991 Embryonic and +1, -15 gm). Embryos/female fetal mortality declined (8.0, 7.3, 6.6, 6.3)

Rats 0,10% SW Subcutaneous administration of et al. 1993 Protection from cooking oils lowered embryo Smith et al. 1994 embryotoxins death.

Rabbits 0, 5,10% SW Body wt. declined (-7.6, -10.6, et al. 1993 Nutritional and -16.8%). Blood serum was reproductive altered. Delayed births responses

Ewes 0, 12.5, 25% SW Trial 1 et al. 1990 Estral activity Estrous cycle increased (17.0, 17.4, 17.8 d). Serum triglycerides decreased (21.8, 14.0, 10.8 mg/d) 0,10% SW Trial 2 Control ewes had normal estral activity (7 of 7 ewes). 10% SW ewes had lower estrus (4 of 7 ewes).

Ewes 0, 12.5, 25% SW Blood serum was altered Martinez et al. 1993 Reproduction in Reproduction was not different. Late gestation

Ewes 0, 25% SW Blood serum altered Berndt et al. 1995 Endocrine function Body wt. was not different and pregnancy Pregnancy rates not different

Ewes 0 and 20% SW Lutienizing hormone levels Padilla et al. 2001 Effects on liver increased but sorbitol dehydro- and reproduction genase hormone was not effected Reproduction was not effected.

Heifers 0, 7.5,15% SW Total BW gain was less (62.4, Williams et al. 1993 Beef heifer 55.2, 51.6 kg). Conception rates performance and body condition scores the same. Direct bilirubin was elevated. Serum creatine kinase activity increased. Elevated serum AST. Higher triglicerides. Elevated creatinine. Decrease blood urea nitrogen. No overt toxicosis evident. Breeding and conception rates the same.

Heifers 0, 5, 30% SW Birth rate and heifer gain the Martinez et al. 1993 same. No toxic symptoms. Reproduction not different.

Cows Effect of dietary Protein supplementation Strickland et al. 1998 supplementation on SW toxicosis improves animal tolerance to Fed hay, corn, or snakeweed protein supplement

I Sw = Snakeweed alfalfa hay (controls) or diets mixed with chopped and mixed with the alfalfa. placed with the heifers and rotated through alfalfa plus 7.5 and 15% snakeweed. Heifers received their respective diets for pens daily. Heifers receiving the snake- Forage intake was restricted to 7.7 kg 98 days. After 42 days of feeding, heifers weed diet gained less weight than the con- daily. Entire snakeweed plants had earlier were estrually synchronized and artificial- trols throughout the trial, however, con- been mechanically harvested, air dried, ly inseminated after which bulls were ception rates and body condition scores

JOURNAL OF RANGE MANAGEMENT 55(3) May 279 were not different. Serum chemistries Strickland et al. (1998) conducted tionship between liver damage and repro- indicated a mild hepato-toxicosis. In a experiments to determine if dietary sup- ductive problems. A major question that similar study, Martinez et al. (1993) plementation could lower snakeweed toxi- remains unanswered related to snakeweed assigned groups of 24 pregnant heifers city effects on beef cows in poor body toxicity is a precise definition of its poiso- (240 days pregnant) to 0,15 or 30% whole condition. Dietary treatments were no nous principal. Without this knowledge it plant snakeweed and chopped alfalfa hay snakeweed and 10% snakeweed mixed is difficult to determine how snakeweed diets. No abortions were recorded for any with 628 g cracked corn and 800 g of a ingestion influences mechanisms of action treatment suggesting that heifers can toler- 42% crude protein supplement provided within the animal (Strickland et al. 1998). ate 15 to 30% snakeweed when fed a base daily. Dry matter intake was limited to diet of alfalfa. Martinez et al. (1993) con- 1.3% of body weight. Bromosulphothalein Snakeweed Impact on Animal and ducted another study with ewes in late (BSP) clearance tests were conducted to Forage Loss gestation feeding either alfalfa or a 25% determine the liver's ability to catalyze Direct animal health problems from snakeweed-alfalfa based diet. As with the phase II biotransformations. Snakeweed snakeweed consumption, such as abortion heifers, no abortions were noted in the consumption did not influence the elimi- and death, were recognized as an impor- ewes and lamb birth weights were unaf- nation of BSP but the exchange rate from tant range management concern in the fected. It is important to note that both the blood to other tissues was accelerated. 1920's and 1930's (Mathews 1936, Smith Williams et al. (1993) and Martinez et al. Supplementation with corn or protein et al. 1991). How widespread the problem (1993) fed whole plant snakeweed rather increased the clearance rate of BSP. This is today is not known but some estimates than fresh or new growth clippings. suggests that if the nutrient status in an are available. Based on a survey of county Oetting et al. (1990) and Edrington et al. animal is improved, then there may be a agents in west , snakeweed poison- (1991) indicated that fresh leaf material is greater tolerance to toxicants metabolized ing causes 1 % annual death loss in cattle likely to be more toxic than whole plant by phase II biotransformations. In unpub- and a 2.9% annual abortion rate (Torell et snakeweed samples. lished data from this experiment, serum al. 1988 from McGinty and Welch 1987). Berndt et al. (1995) conducted experi- progesterone and estrogen concentrations Sheep and goat death losses were an esti- ments to determine if new-growth snake- did not differ among the 0 and 10% snake- mated 0.7% and 0.4%, respectively, weed placed directly into ruminally cannu- weed diets or supplementation types. Also, whereas abortion losses were 1.3% and lated ewes would alter the sensitivity of ovarian follicular development was not 0.7%, respectively. As is the case with the pituitary gland to gonadotropin-releas- affected by snakeweed or supplements. many poisonous plants, however, general ing hormones (GnRH). In their first exper- Subsequently, 2 additional trials have estimates of loss are often not very mean- iment, 8 ewes received no snakeweed or been conducted at NMSU to determine the ingful because it is specific damage to a 25% as a snakeweed portion of a blue effects of snakeweed on biotransformation particular animal, herd or ranch operation grama grass hay diet. After 35 days on the mechanism in sheep. Padilla et al. (2001) that is most important. Thus most diets, ewes were administered 10 pig of compared pair-fed wethers having diets researchers agree that snakeweed related GnRH and blood was collected at 15 containing 0% or 20% snakeweed on a dry losses, such as abortion and birth-related minute 5 intervals for hours. After blood matter basis. Caffiene and BSP clearance abnormalities in cattle, sheep and goats are sampling, ewes were joined with fertile were measured to evaluate the ewes ability sporadic and vary widely by location, sea- rams. The luteinizing hormone response to to eliminate xenobiotics. Caffiene clear- son, climate, soil, and range conditions GnRH was significantly higher in ewes ance was not different between treatments (Norris and Valentine 1957, Martinez et receiving 25% snakeweed compared to but wethers consuming snakeweed exhib- al. 1993, Williams et al. 1993). animals eating only blue grama hay. ited reduced (P < 0.05) BSP clearance. In Indirect animal health problems result- Treatments continued for 68 days after a second experiment, Padilla et al. ing from emaciation, malnutrition, and which ewes were euthanized and pregnan- assigned 10 ewes to either a 0% or 20% lack of gain on rangeland densely infested cy status was determined by examination snakeweed diet and animals were again with snakeweed is a greater economic bur- of uterine tissue. Pregnancy rates were pair-fed to equalize intake. Blood samples den to livestock producers than snakeweed unaffected by snakeweed ingestion. In a were collected to measure luteinizing hor- poisoning (Torell et al. 1988). Grass pro- second experiment by Berndt et al (1995) mone (LH) and sorbitol dehydrogenase duction can be decreased by 90% or more alfalfa hay was used instead of blue grama (SDH) which is a liver specific enzyme. in extremely dense snakeweed stands as the base diet. Ewes were fed below Animals fed the snakeweed diet had high- (McDaniel et al. 1982). Lack of suitable NRC (1985) requirements similar to the er baseline concentrations of LH but SDH forage in the presence of snakeweed first experiment. After 29 days on 0 or concentrations were not different from the necessitates livestock producers to either 25% snakeweed diets, a GnRH challenge control diets. The authors suggested that provide a supplement, drastically reduce was conducted. Unlike the first experi- the elevated LH in ewes consuming snake- stocking rates, and/or remove the weed. ment, no differences were found for weed was due to a high lipid content in the Whatever alternative is chosen, the cost to luteinizing hormone response. The authors plant. Ewes were exposed to fertile rams producers is high. Economic losses from indicated that the nutritive quality differ- and pregnancy rates in these experiments snakeweed varies depending on beef ences between blue grama and alfalfa hay were similar for both diets. prices and production cost, but on the 10 base feed diets was probably most respon- Current research at NMSU is evaluating million ha of rangeland in the western sible for the differences in pituitary different extractions of snakeweed to iden- United States infested with snakeweed, response to GnRH shown in these 2 exper- tify specific toxicants. Also, experiments losses are substantial (McDaniel and iments. are being conducted to determine the rela- Tore111987).

280 JOURNAL OF RANGE MANAGEMENT 55(3) May 2002 SnakeweedlGrass Interaction 1000 The snakeweed-overstory and grass- understory biomass relationship has been expressed using sigmoidal growth and negative exponential equations (McDaniel et al. 1993). The downward sloping con- Burning Control vex shape of an exponential equation implies that grass production is retarded with even a minor snakeweed presence, thus for management purposes control 500 P strategies that maximize snakeweed removal are likely to be most economical- ly efficient (Tanaka and Workman 1988). The sigmoid shape (Fig. 1) implies that a Herbicide Control minor amount of snakeweed does not affect grass biomass but that once a threshold is reached then grass biomass is drastically reduced, i.e. in a manner simi- lar to that estimated by a negative expo- nential equation. 0 300 600 900 1200 Having an appreciation of the snake- weed-overstory and grass-understory rela- Increasing Snakeweed Biomass (kg/ha) tionship has practical management impli- cations when trying to decide whether to Fig. 1. Sigmoid curve illustrating the snakeweed-overstory and grass-understory relationship use prescribed fire or a herbicide to con- and areas where burning or herbicide control become most practical. trol snakeweed (Fig. 1). For example, in areas with a moderate to dense amount of been described in part elsewhere and length of time they might survive in a snakeweed (areas with >300 kg/ha snake- (McDaniel 1989, McDaniel and Duncan given area is neither repeatable or pre- weed), burning is usually impractical 1987). At these locations, data were dictable thus the term "cyclic" must be because fine fuels are often insufficient in acquired from replicated untreated plots used in a restrictive sense when describing quantity and uniformity to carry a fire (0.1 ha in size) placed in pastures that had snakeweed populations. A 100-year record (McDaniel et al. 1997). Rangelands with a high initial density of snakeweed. Blue set from permanent quadrats placed on the high amounts of snakeweed are generally grama was the principal associated grass. Joronada Experimental Range in southern better managed with an aerial herbicide Over the 20-year study period landowner- New Mexico indicated that the average application than fire. Where light amounts ship did not change and, in general, the life expectancy for snakeweed was about 4 of snakeweed and sufficient grass occur (< ranchers employed consistent grazing years, but that some individual plants lived 300 kg/ha snakeweed and > 500 kg/ha of management practices through time. longer than 15 years (Dittberner 1971). grass), then prescribed fire is often a better Figure 2 indicates that during years when There was no indication from the Joronada management choice than herbicide control snakeweed was highly dominant, such as data set that the snakeweed population because it is less costly. An expectation in the early 1980's, grass growth was was predictably cyclic over time. after employing either control method is highly suppressed. Only after snakeweed Environmental events that influence that a favorable grass response will offset naturally declined at these locations did snakeweed seed production (Wood et al. treatment cost (Torell et al. 1988). grass yield increase. Typically, grass yield 1997), trigger germination (Kruse 1979, Rangelands dominated by snakeweed increases 4 to 6 fold after a dense snake- Mayeux and Leotta 1981, Mayeux 1983), are often perceived as being in poor range weed stand dies-out or when the weed is and affect survival (McDaniel 1989) are condition because grass growth languishes removed by herbicide spraying (McDaniel becoming better understood. Close study beneath dense canopies. However, caution et al. 1982, McDaniel and Duncan 1987). of seedling establishment suggests that the must be exercised to distinguish between optimal environmental conditions neces- what might be poor forage condition as How Snakeweeds Longevity Effects sary for propagation occur only once or opposed to poor ecological (range) condi- Management Decisions twice a decade in the southwestern United tion. Rangelands with dense snakeweed Snakeweed populations have been States. Snakeweed seedlings have been may or may not be in poor range condi- described in the literature as cyclic noted after above-average winter precipi- tion, but they are nearly always in poor through time (Jameson 1970). That is, tation in the Chihuahuan Desert of south- forage condition. To further illustrate the propagation occurs under favorable envi- ern New Mexico (Barnett 1996, Beck et importance of understanding the oversto- ronmental conditions and plants survive al. 1999), and with above-average spring ry-understory relationship, Figure 2 shows until conditions become unfavorable, then precipitation on blue grama rangeland in a 20 year comparison of snakeweed and they die. The term cyclic implies a regular central New Mexico (McDaniel et al. grass biomass taken from undisturbed and repeated life history pattern that is 2000). Die-offs from weather usually research plots near Vaughn and Roswell, expected to occur over many years. In result from summer drought but insects New Mexico. A portion of this data, and actuality, the number of snakeweed plants and old age are also responsible for natural the manner in which it was collected has plant losses (Pieper and Mc Daniel 1989).

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Y 4 cY , /%SD\ qs_ J 0çZ) ç #y 3?&??:&/c0 . . £\ ... Zj\ . 5 . . :ç5p o' t% :Z';%; .' :% , ° , / %/ '' o . , ' 44 4? c 7# ,, - , /1 , ., . V \'b , zP \&, \ \0 c0 0 . . _ - . ,g . ? . A0 ,-\Cb:s'-? o\# -# F , 4 : :c , 4y ,\. c:cC;:: , \' d%?0: ,/, c;0; c ' '4)' . , . , C, ' :# \ ,, 's"t0 c0\ ç z *s çs ; ' s --<:- \o'/ &; , 0 a 9 C, Table 2. Snakeweed control 12 months after Literature Cited Kruse, W. H. 1979. Temperature and moisture spraying with piclorami, and subsequent stress affect germination of Gutierrezia evaluations made in 1988 and 1999 near sarothrae. J. Range Manage. 23:143-45. Vaughn, N.M. Beck, R. F., R. P. McNeely, and S. J. Muir. Lane, M. A. 1985. of Gutierrezia 1996. Effects of goats and drought on snake- (Composiate: ) in North America. Year 1st yr after weed. Abstract in 49th Ann. Meeting of Soc. Syst. Bot. 10:7-28. Sprayed treatment 1988 1999 for Range Mangement pp. 7. Feb. 10-15, Martinez, J. H., T. T. Ross, K. A. Becker, J. ---- % Snakeweed Control----- 1996. L. Williams, D. Campos, and G. S. Smith. Beck, R. F., M. 1979 98 25 0 Nsinamwa, R. Santos, and R. 1993. Snakeweed toxicosis in late gestation D. Pieper. 1999. Dynamics of Gutierrezia 1980 95 3 0 ewes and heifers. In: Sterling, T. M. and D. sarothrae with drought and grazing. In: C. Thompson (eds.).pp. 48-49. Snakeweed 19812 -- -- Eldridge and Freudenberger. 502-504. 1982 83 83 pp. Research: Updates and Highlights. New Proc. of the VI Internat.. Range Congress, Mexico Agric. Exp. Stn. Res. Report #674. 1983 100 100 Vol.1, Townsville, Australia. 1984 99 99 Mathews, F. P. 1936. The toxicity of Berndt, M. Y., T. T. Ross, and D. E. broomweed (Gutierrezia microcephala) for 1985 99 99 Hawkins. 1995. The effects of snakeweed sheep, cattle, and goats. J. Amer. Vet. Med. 1986 100 99 (Gutierrezia microcephala and G. sarothrae) Assoc. 88:56-61. 1987 100 100 on endocrine function and establishment of Mayeux, H. S., Jr.1983. Effects of soil texture 1988 100 100 pregnancy in ewes. In: Proc. West. Sect. and seed placement on the emergence of four 'Picloram applied at 0.56 kg/ha in 1979, 1980, and 1982; Amer. Soc. Anim. Sci. 46:69-72. . Weed Sci. 31:380-84. applied at 0.28 kg/ha in 1983 to 1988. Barnett, B. L. 1996. Influence of winter pre- Mayeux, H. S. and L. Leotta. 1981. No treatments made in 1981. cipitation on broom snakeweed establishment Germination of broom snakeweed and in the Chihuahuan Desert. M.S. Thesis. New threadleaf snakeweed. Weed Sci. Mexico State Univ., Las Cruces, N.M. resulted in the treated areas to appear simi- 29:530-534. Cox, S. H. 2000. Snakeweed (Gutierrezia spp.) McDaniel, K. C. 1989. Use of herbicides in lar to nonsprayed rangeland within a few consumption by grazing beef cattle. M. S. snakeweed management.In: Snakeweed: years of treatment. However, areas sprayed Thesis. New Mexico State University, Las Problems and Perspectives. E. W. at the Vaughn location in 1982 or later have Cruces, N.M. Huddleston and R. D. Pieper (eds.). pp. remained essentially snakeweed free for the Chambers, S.W., G.S. Smith, M. S. Stavanja, 85-99. New Mexico Agr. Exp. Sta. Bull. E. C. Staley, P. Thilstead, and D. M. next 18 years. J. 751. Hallford. 1993. Safflower oil protects rats Eliminating snakeweed by herbicide or McDaniel, K. C. and K. W. Duncan. 1987. from embryotoxins of ingested snakeweed Broom snakeweed (Gutierrezia sarothrae) fire result in an increase in control can foliage. Proc. West. Sec. Amer. Soc. of control with picloram and metsulfuron. Weed rangeland carrying capacity and can also Anim. Sci. 44: Sci. 35:837-41. reduce livestock losses caused by poison- Dittberner, P. L. 1971. A demographic study McDaniel, K. C. and L. A. Torell. 1987. ing and malnourishment. McDaniel and of some semi-desert plants. M. S. Ecology and management of broom snake- Duncan (1987) reported that with 90% or Thesis, New Mexico State University, Las weed. In: Integrated pest management on Cruces, N.M. rangeland, a shortgrass prairie perspective. J. greater snakeweed control with a herbi- Dollahite, J. W. and T. J. Allen. 1959. cide, the carrying capacity at Vaughn L. Capinera (ed.). Westview Press. Boulder, Feeding perennial broomweed to cattle, Cob., 101-15. changed from 1 AU/62 ha to 1 AU/20 ha, swine, sheep, goats, rabbits, guinea pig, and McDaniel, K. C., D. B. Carroll, and C. R. and at Roswell the change was from 1 chickens. Texas Agr. Exp. Sta. PR-2105. Hart. (2000). Broom snakeweed establish- AU/88 ha to 1 AU/7 ha. With commercial College Station, Tex. ment on blue grama after fire and aerial application cost of $22 per ha to Dollahite, J. W. and W. V. Anthony. 1957. herbicide treatments. J. Range Manage Poisoning of cattle with Gutierrezia micro- spray picloram at a 0.28 kg/ha rate, the 53:239-245. cephala, a perennial broomweed. J. Amer. buyer needs at least 4 years of benefit to McDaniel, K. C., C. Hart, and D. B. Carroll. Vet. Med. Assoc. 130:525-30. 1997. Broom snakeweed control with fire on justify the expense (Torell et al. 1988). Edrington, G. S. Smith, M. D. Sanford, J. New Mexico blue grama rangeland. J. Range Cost related to prescribed fire depends on Medrano, T. T. Ross, and J. C. Thilsted. Manage. 50:652-59. the size of the area to be burned and avail- 1991. Ingested snakeweed foliage related to McDaniel, K. C., R. D. Pieper, and G. B. able labor and logistical support. embryonic and fetal mortality of albino rats. Donart. 1982. Grass response following Typically, areas to be burned must be In: Proc. West. Sec., Amer. Soc. Anim. Sci. thinning of broom snakeweed. J. Range 42:12-14. deferred at least 2 growing seasons: one Manage. 35:142.45. Foster, D. E., D. N. Meckert, and C. J. McDaniel, K. C., L. A. Torell, and J. W. season to build up adequate fine-fuel DeLoach. 1981. Insects associated with Bain. 1993. Overstory-understory relation- loads, and a second season for grass broom snakeweed and threadleaf snakeweed ships for broom snakeweed-blue grama recovery (McDaniel et al. 1997). in west Texas and eastern New Mexico. J. grasslands. J. Range Manage. 46:506-11. Combined, chemical control may be Range Manage. 34:446-454. McGinty, A. and T. G. Welch. 1987. viewed as a reclamation tool to reduce Hall, L.E., M.L. Galyean, and T.T. Ross. Perennial broomweed and Texas ranching. 1991. Effect of increasing level of snake- high densities of snakeweed, whereas Rangelands 9:246-249. weed on digestibility of alfalfa and grass hay Miller, R. G. S. Smith, and R. L. Byford. burning control is a tool for maintaining J., in vitro. Proc., West. Sec., Amer. Soc. Anim. 1993. Nutritional, toxicological, and repro- non-economic populations of snakeweed Sci. 42:292. ductive responses in female domestic rabbits (Sterling et al. 1999). Jameson, D. A. 1970. Value of broom snake- fed snakeweed foliage. In: Proc. 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JOURNAL OF RANGE MANAGEMENT 55(3) May 283 NRC.1985. Nutrient requirements of sheep (6`h Smith, G.S. and G.I. Flores-Rodriguez.1989. Strickland, J. R., L. F. Gulimo-Klein, T. T. edition). National Academy Press, Toxicity of snakeweeds. In: Huddleston and Ross, S. Slate, M. K. Petersen, T. May, and B. Taylor. 1998. Effects of nutrient Washington D.C. Pieper. pp. 211-219. Snakeweed: Problems J. in beef cows of poor body Oetting, B. C., T. T. Ross, K. Walraven, P. and Perspectives. NMSU Agr. Exp. Bull. supplementation Kloppenburg, G. S. Smith, and D. M. condition fed snakeweed (Gutierrezia spp.). 751. 40:278-284. Hallford. 1990. Effects of ingested snake- Vet. and Hum. Tox. Smith, G. S., T. T. Ross, G. S. Flores- A. P. Workman. 1988. weed herbage on actual activity, blood prog- Tanaka, J. and J. Rodriguez, B. C. Oetting, and T. S. Economic optimum big sagebrush control for esterone, and serum clinical profiler of fine- Edrington. 1991. Toxicology of snake- increasing crested wheatgrass production. J. wool ewes. In: Proc. West. Sect. Amer. Soc. weeds, Gutierrezia microcephala and G. Range Manage. 41:172-178. Anim. Sci. 41:23-26. sarothrae. In: James, Evans, Ralphs, and Thompson, D. C., K. C. McDaniel, L. A. Padilla, D. J., T. T. Ross, J. P. Strickland, D. Child. pp. 236-246. Noxious Range Weeds. Torell, and D. B. Richman. 1995. Damage M. Hallford, M. W. Salisbury, and J. L. Westview Press, Boulder, Colo.. potential of Hesperotettix viridis (Orthoptera 2001. Effects of snakeweed Bollinger. Smith, G. S., T. T. Ross, D. M. Hallford, J. P. Accidental) on a rangeweed, Gutierrezia (Gutierrezia ingestion on reproduction spp.) Thisted, E. C. Stales, J. A. Greenberg, and sarothrae. Environ. Ento. 24:1315-1321. and liver function in sheep. Proc., West. Sec., R. Miller. 1994. Toxicology of snake- Torell, L.A., H. W. Gordon, K. C. McDaniel, Amer. Soc. Anim. Sci. 52:45-49. J. weeds (Gutierrezia sarothrae and G. micro- and A. McGinty.1988. Economic impact of Pieper, R. D. 1989. Broom snakewood content cephala). Proc. West. Sec. Anim. Soc. of perennial snakeweed infestations. In: The of herbivore diets. In: Snakeweed: Problems economic impact of poisonous Anim. Sci. 45:98-102. ecology and and Perspectives. E. W. Huddleston and R. plants on livestock production. James, L. F., Solbrig, 0. T. 1960. Cytotazonomic and evolu- D. Pieper (eds.). pp. 203-10.New Mexico M. H. Ralphs, and D. B. Nielson (eds.) tionary studies in the North American species pp., Agr. Exp. Sta. Bull. 751. 57-69. Westview Press. Boulder, Colo. Pieper, R. D. and K. C. McDaniel. 1989. of Gutierrezia (Composiate). Controb. Gray Williams, J. L., D. Campos, T. T. Ross, G. S. Ecology and management of broom snake- herb. 188:1-61. Smith, J. M. Martinez, and K. A. Becker. weed. In: Snakeweed: Problems and Solbrig, 0. T. 1964. Intraspecific variation in 1993. Heifer reproduction is not impaired by Perspectives. E. W. Huddleston and R. D. the Gutierrezia sarothrae complex snakeweed consumption. In: Sterling, T. M. Pieper (eds.). New Mexico Agr. Exp. Sta. (Compositate-Asteraceae). Contrib. Gray and D. C. Thompson (eds.). Snakeweed Bull. 751,1-12. Herb. 193:67-115. Research: Updates and Highlights. New Richman, D. B. and D. C. Thompson. 1995. Sterling, T. M.., D. C. Thompson, and K. C. Mexico Agr. Exp. Sta. Res. Report 674: Insect associations with woody snakeweeds McDaniel. 1999. Snakeweeds. In: Biology 46-47. in New Mexico, Texas, and . In: and Management of Noxious Rangeland Wood, B. L., K. C. McDaniel, and D. Clason. Papers from the Fourth Symposium on Weeds. R. L. Sheley and J. K. Petroff (eds). 1997. Broom snakeweed (Gutierrezia Resources of the Chihuahuan Desert Region. Oregon State University Press, Corvallis, sarothrae) dispersal, viability, and germina- Chihuahuan Desert Res. Inst., Alpine, Tex.. Ore. tion. Weed Sci. 45:77-84.

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