RANGELANDS11(6), December1989 261 the ranch'sprogress or decline in overallrange condition the rangeon a short-term basis (i.e., determinethe proper if photographedplots are permanently markedand esti- stocking rateor the propergrazing cycle length),and can mated each 5 or 10 years. providea reliablevisual record of the manager's ability to This photographicmethod aids in the management of improveit.
Senecio: A Dangerous Plant for Man and Beast A.E. Johnson, R.J. Molyneux and M.H. Ralphs
The genusSenecia includes 1,000 to3,000 species dis- Riddell'sgroundsel (S. riddellii) occurs in the Mid- and tributed throughout theworld. Senecioand other species Southwest. It is a suffrutescenthalf-shrub that dies back that contain pyrrolizidine alkaloids (PA) [i.e., hounds to the crown each fall and thrives on sandy soil. It is tongue (Cynoglossurn officinale), fiddleneck (Arnsinckia similar in appearance tothreadleaf groundsel except that intermedia),and speciesof Crotalaria,Borago, Heliotro- its leaves and stemsare bright green.It was implicatedas pium and Echiurn]are perhapsthe most importantgroup causing "walking horse"disease early in this centuryand of poisonous plants worldwide. They are toxic to live- has systematicallybeen eradicated in many areas of the stock when grazed or ingested in hay or contaminated Midwest (Barkley 1978). grains. They are also toxic to humanswhen ingested as Toxicology contaminantsin cereals, from PAcontaminated milk pro- Estimates of toxicity of Seneciospecies are ducts commonly (PA's ingested by lactating animalsare excretedin based on the amount of plant required to cause symp- the milk), andwhen made into herbalteas. Tansy ragwort toms or death.These estimates are not reliableor realistic (Seneciojacobaea)is often confusedwith tansy(Tanace- because toxicitydepends on the PAconcentration in the turn vulgare), which has been used in herbal medicines plant, the specific PA present, theform of PA, and the rate (Cheeke and Shull 1985). Comfrey (Symphyturnof fici- at which the plant is ingested. which has been nale), reputed as havingmedicinal prop- There are many different PAs. The majority are toxic erties, also contains PA. and affect the liver. contains 8 In the western primarily Tansy ragwort US, only7 Seneciospecies are reported PA5, threadleaf groundsel contains4, and Riddell's to be toxic but ground- (Kingsbury 1964), many other species sel contains only 1. Each PA exists in the plant as a probablycontain PA. The greatesteconomic loss is from nontoxic free-base or a N-oxide. become toxic cattle Horses are also They poisoning. highly susceptibleto whenthe free-baseis converted into highly reactive PA, but and are moreresistant and bean alky- sheep goats may lating pyrrolesby liver microsomal enzymes. The N-oxide effective biological control for some Seneciospecies. must first be convertedto the free-base, in Three Senecio presumably species cause the majority of cattle the gut, before conversion to the pyrrole. the losses in the western US. was introduced Initially Tansy ragwort free-base form was considered potentially more toxic from Europeand occurs in the coastal PacificNorthwest et al. 1 985b), butrecent evidence that and in the (Johnson suggests Northeast.The plant is a weedy winter annual the N-oxide can be equally toxic (Molyneuxet al. or biennial that in the over-wintersas a 1989). germinates fall, Thus, the total PA content of a species is currently the rosette, and forms a tall flowering stalk in the spring and best estimate of its It toxicity. summer. growson moist well-drained soils in pastures, The reactivepyrrole crosslinkswith DNAand prevents forests, and wastelands. livercells from As thecells senesce and Threadleaf reproducing. die, or woolly groundsel(S. douglasiivar. longi- they are not replaced. Increasingnumbers of liver cells in the Southwest. It is a low- lobus) grows principally are damaged with each successive toxic dose of PA, growing, perennial, evergreen shrub and is most abund- resulting in a cirrhosis-like liver condition with blocked ant on loamy to clay soils. Its leaves and stems are bileducts andveins. Thesechanges lead to eventual liver coveredwith awhite woolly pubescence. It is an increaser failure anddeath of the animal. Thedisease is progressive that becomes abundanton abused and species degraded and symptomsmay not becomeapparent for3 weeks up rangeland. to 18 months after ingestion of the plant. Thus, a large Editor's Note: 1 pound (Ib) equals 454grams (g) proportion of deaths and illnesss may go undiagnosed. 1 kilogram (kg) equals 2.2 pounds Johnson and Ralphs are atthe USDA Agr. Res. Serv. Poisonous Plant Lab, Logan UT84321; Molyneux is atthe USDAAgr. Res. Ser. WesternRegional ResearchCenter, Albany, CA 94710 262 RANGELANDS 11(6), December1989
a. TANSY RAGWORT
.9 1979 ——1980 —-1981 It .8 / \ .7 1/' .6 / ,1 / \ , I / \ .5 ———,, / 1/ .4. / :l••. ' \\ \\ / . . \ .3. / . — . 0 0 .2 .1
I I • I • I JAN FEB MARAPR MAYJUN JULAUGSEPOCTNOVDEC
b. THREADLEAFGROUNDSEL 'I
1979 8 —- 1980 — -1981 7 1982 6 5
3 2
1 a FEB MAR APR MAY JUN JUL AUG SEP OCT NOV
C. RIDDELL'S GROUNDSEL
FIg.1. Pyrrolizidine alkaloid content ofleaves of three Senecio species: (a) tansy ragwor: collectedat Roseburg, OR. (b)threadleafgroundselcollectedat Sonita, AZ; (c) Riddells groundsel collectedat Woodward,OK RANGELANDS11(6), December1989 263
The acute or chronic natureof the disease depends on Table 1. ToxIcityof S.neclospecIes fed to220 kg calves for20 days. how much plant and PA are consumedand how rapidly they are ingested. There appears to be a threshold of PA Lethal amountof tolerance the plant by the liver,or pre-absorbance influencesin level in gut, that must beexceeded beforePA becomedangerous Species lethal dose plant Dry Fresh4 and Animals can eat small (Johnson Molyneux 1984). mg/kg amounts of Senecio over periods of time without any body wt % ------9/day---—- adverseeffects. Abovethe threshold level,Seneclo ingested Tansy ragwort 2.3' .31 161 806 for 15 to 20days may lethallydamage the liver.In time, or Threadleaf due to groundsel 10132 2.19 118 594 stress, the liver may fail to function properly,and Riddell's groundsel 15-2O 6.40 63 312 theanimal eventually dies.Acute poisoning israre because Riddell's groundsel of the low palatability of Senecio species. However, if High PA 15-20 18.0 22 111 animalsare forcedto eat large quantitiesof PA-containing Johnson 1979 2Johnson and Molyneux 1984 plants in a short time, necrosis in the liver and severe 3Johnson etal. 1985a hemorrhage causesdeath within 1 to 2 days (Kingsbury 4Based ondry matter content of 20%. 1964). Younger animals are more susceptible to PA because when plantsare flowering.PA content of Riddell'sground- of increased cellular activity and higher levels of PA sel is lowest when it starts growth in the spring and metabolizing enzymes in the liver (Johnsonet al. 1985a). increases as the plant matures. Maximum hazard is in Clinical signs include a rough, unkept appearance; diar- mid-summerduring the bud and flower stage. rhea; prolapsed rectum; bloated appearance; lassitude These Senecio species are not very palatable to live- and dullness; neurological disturbances, such as "head stock. However, ifthey are presenton rangeor pastures, pressing" againstsolid objects; andrestless pacing (Cheeke cattle shouldbe watchedclosely tosee ifthey are grazing and Shull 1985). Senecio, and removed if they begin to selectthem. When PA contentvaries amongspecies, within seasons, and PA content is high, only a small amountof plant material between years (Fig. 1). The level of PA in Riddell's needs to be consumedover 15 to 20 days to be lethal to groundselis extremely high. The peak PA concentration young cattle. in leaves exceeded 10% of dry weight in 5 consecutive Sheep are moreresistant to PAtoxicity and manyselec- years of sampling (Molyneux and Johnson 1984). The tively graze Senecio. Thus, they can be used to reduce extremePA content in Riddell'sgroundsel at Woodward, Senecio availabilityfor cattle (Sharrow and Mosher1982). OK, in 1980 (Fig. 1-c) occurred in ahot, dryyear. Alkaloid Other biological agents such as the cinnabarmoth and levels rarelyexceed 7% inother species specificallyculti- the ragwort flea beetle are effective in controlling tansy vated fortheir alkaloids. Drought stress can increase PA ragwortwhen they can beestablished in coloniesof suffi- content of Senecio (Briskeand Camp1982). cient strength. Herbicides such as 2,4-D applied in the Of the three speciesstudied, PA in tansy ragwort are spring or dicambaapplied in early summerare also effec- most toxic, requiring only2.3 mg PA/kgbody weight/day tive controls. Threadleaf groundsel can be controlled fora lethal dose(Johnson 1979). The largernumber of PA with 2,4-D plus picloram (0.8 + 0.3 kg a.e./ha) applied in andtheir differing toxicity probablyaccount for its higher theautumn when plants are activelygrowing, and metsul- toxicitycompared to the other2 species. The flowers are furon at rates as low as 18 g ai/ha is also promising most toxic, followed by leaves, then roots. The stemsare (Sharrow et al. 1988). relativelynontoxic (Swicket al. 1979). However, theaver- Literature Cited age PA content in thetansy ragwort plant is lowestof the the Barkley, TM. 1978. Senecio. North America Flora Series II, Vol. three species studied (0.31% of dry matter). Thus, 10:50-139. amountof fresh plant materialrequired for a lethaldose is Blrske, D.D., and B.J. Camp. 1982. Water stress increasesalkaloid greater than the otherspecies (Table 1). The toxicityof concentrations in threadleaf groundsel (Senecio Iongilobus). threadleaf is intermediate and Weed Sd. 30:106-108. groundsel (Johnson Moly- 1985. Natural Toxicants in Feedsand PA Riddell's are least toxic Cheek., P.R.,and LR.Shull. neux 1984). of groundsel PoisonousPlants. AVI Pub. Co., Westport,CN. pp 93-118. (Johnsonet al. 1985a). However, Riddell'sgroundsel had Johnson, A.E. 1979. Toxicityof tansy ragwort to cattle. pp 129-134 the concentrationin the plant (6.4%).At In:P.R. Cheeke(ed), Symposiumon pyrrolizidine (Senecio)alka- highestaverage mea- extremeconcentration 18% PA, 111 of loids: Toxicity, metabolism and poisonous plant control the of only g/day sures. NutritionResearch Institute, OregonState Univ.,Corvallis, fresh plant materialfor 20days would be requiredto kill a OR. 220 kg calf (Table 1). Johnson, A.E., and R.J. Molyneux. 1984. Toxicity of threadleal groundsel (Seneclodouglesli var Iongilobus) to cattle. Am.J. Vet. Management Res. 45:26-31. PA content of tansy ragwort can be high during any Johnson, A.E., R.J. Molynsux, andL.D. Stewart.1985a. Toxicity of month due to its flexible biannualgrowth form. There is Riddell's groundsel (Senecio riddellil)to cattle. Am. J. Vet. Res. no safe grazing period. The maximum hazard from 46:577-582. Johnson, A.E., R.J. Molyneux,and G.B.MerrIll. 1985b.Chemistry of threadleaf groundsel is from mid-summerthrough fall toxic range plants. Variation In pyrrolizidine alkaloid contentof Senecio,Amsinckia, and Crotalariaspecies. J. Agric. Food Chem. 33:50-55. 264 RANGELANDS11(6), December1989
Kingsbury, J.M. 1964. Poisonous Plants of the United States and Sharrow,S.H., ON. Ueckert, and A.E. Johnson. 1988. Ecology and Canada. Prentice-Hall,Englewood Cliffs, NJ. toxicology of Senecio specieswith special referenceto Seneclo Molyn.ux, R.J., and A.E. Johnson. 1984. Extraordinary levels of jacobaeaand Senecio Ion gilobus. pp181-196 In:L.F. James, M.H. production ofpyrrolizidine alkaloids in Senecioriddellhi. J. Natural Ralphs, and D.B. Nielsen (eds), The Ecology and Economic Products47:1030-1032. Impact of Poisonous Plants on Livestock Production. Westview Moiyn.ux, R.J., A.E. Johnson, J.D. Olsen, and D.C. Baker. 1990. Press. Boulder, CO. Toxicityof pyrrolizidine alkaloidsfrom Riddell'sgroundsel (Sene- Swick, R.A.,P.R. Cheeke,and D.R. Buhier. 1979. Factors affecting do riddellii)to cattle. Am. J. Vet. Res. (In press). the toxicityof dietary tansy ragwort to rats. pp. 115-123 In: P.R. Sharrow, H.S.,and W.D. Masher.1982. Sheep as a biological control Cheeke (ed.), Symposium on pyrrolizidine (Senecio) alkaloids: agent for tansy ragwort. J. Range Manage. 35:480-482. toxicity, metabolismand poisonousplant control measures. Nutri- tion Research Institute, Oregon State Univ., Corvallis, OR.
Goats Make "Cents" out of the Scourge of Leafy Spurge Sierra Stoneberg Sophomore Sierra Stoneberg HinsdaleHigh School Hinsdale, Montana
These days, ranchersall over Montanaare searching the parentplant and can survivein the soil undamaged for forthe answer to this question: Howdo you deal with the eight years. scourgeof leafy spurge?Today, this noxiousweed cov- Onemethod for leafyspurge control is applyingchemi- ers well over half a million acres of Montana rangeland. cal herbicides. The chemical most effectiveon spurge is Thousands of dollarsare literallypoured into spurgecon- Tordon. Minimum control requires half a pound of Tor- trol every year, yet leafyspurge continues to spread—and don mix an acre. That would cost at leasttwenty dollars spread—and spread. As anyonewho has it on their place per acre. Forgood control it is necessary to use twicethat, can tell you, S.P.U.R.G.E. is just anotherway to spell big which costs about 40-45 dollars an acre. If the spurge is trouble. sprayed every year it probablywon't spread, but if given The latex in spurge is a face irritant to cattle and they even half a chance, it will come back as strong as ever. avoid it. Inovergrazed areas, thecattle will eateverything Also, leafyspurge prefersriparian areas where it is dan- in sight—with the exceptionof the spurgeand any plant gerousto humansand animalsalike to introducechemi- growing directly within the spurge patch. Grazing leafy cals. In addition, the amount of herbicide necessary to spurge with cattle—or even horses—actually helps the damage aspurge plant can injure grasses, trees and other spurge, by removing its competition. desirable plants as well. So even though chemicals will Spurge(a Eurasian plant probablybrought to Montana control spurge and stop it from spreading, they cost a in hayfrom North Dakota) is not only hereto stay,it's here great deal, and the land that was spurge infested cannot to take over! alwaysbe reclaimed for grazing. Leafy spurge iswell suitedto its conquestof Montana. Anothercontrol possibility is severe cultivation.This is It's a hardy plant and none of its natural enemies are nota very feasibleoption for Montana's ranges, because nativeto anywhere in the whole United States. Itspreads they are in most cases difficult to plow and leafyspurge's like a wild fire by means of its extensiveand powerful root roots are so hardy. system, which is coveredwith small pinkbuds that sprout The idea of control with insects (which may soon into new plants. Most plants will die if you keep their top becomeaveryreal possibility) is onlyin its relatively early growth cut back so that they can't photosynthesize. Not stages. It will probably be a number of years before a leafyspurge! Spurge hasthe ability to store phenomenal workableinsect spurgecontrol programis available. Until amountsof glucose in its roots and can survivefor years then,we can't afford to bury our heads in thesand. Some- on the nutrients stored there alone. A tiny piece of root thing must be done—and now. onlyhalf an inchlong and atenth of an inch thickcan still One possibility is the goat. Goatslove leafyspurge. It's grow into a whole new plant. truethat there isn't a very ready marketfor goat cheese in Leafy spurge also reproduces at run-away rates by Montana; however, there are moregoats aroundthan just seed. A single stalk can produce as many as 140 seeds. dairy goats. One that fits the need nicely is the Angora. They are explodedfrom their pods up to fifteen feet from Angorasare raised formohair, a strong type of hair that makes aversatile, shiny yarn. It has many of the qualities Editor's Note: This isthe first place paperat the High School Youth of wool, but is less irritating to the skin. It is used for Forum Contestfrom Billings, Montana,Feb. 1989.