Senecio vulgaris explained

Senecio vulgaris, often known by the common names groundsel[1] and old-man-in-the-spring, is a flowering plant in the family Asteraceae. It is an annual herb, native to the Palaearctic and widely naturalised as a ruderal species in suitable disturbed habitats worldwide.

Description

Senecio vulgaris is an erect herbaceous annual growing up to 16inches tall.[1] The inflorescences usually lack ray florets, the yellow disc florets mostly hidden by the bracts giving the flowers an inconspicuous appearance. Senecio vulgaris is very similar to Senecio viscosus but S. vulgaris does not have the glandular hairs and ray florets found in S. viscosus.[2]

Leaves and stems

Upper leaves of Senecio vulgaris are sessile, lacking their own stem (petiole), alternating in direction along the length of the plant, two rounded lobes at the base of the stem (auriculate) and sub-clasping above. Leaves are pinnately lobed and +2.4inches long and 1inches wide, smaller towards the top of the plant. Leaves are sparsely covered with soft, smooth, fine hairs. Lobes typically sharp to rounded saw-toothed.[3]

The hollow[4] stems branch at the tops and from the base. Stems and leaves can both host the Cineraria leaf rust.

Flowers

Open clusters of 10 to 22 small cylinder shaped rayless yellow flower heads to inch (6 to 13 mm) with a highly conspicuous ring of black tipped bracts at the base of the inflorescence as is characteristic of many members of the genus Senecio. There is a radiate form of Senecio vulgaris, which is the result of cross pollination with the closely related Oxford ragwort, Senecio squalidus.[5]

Seeds

The name for the genus Senecio is probably derived from senex (an old man), in reference to its downy head of seeds; "the flower of this herb hath white hair and when the wind bloweth it away, then it appeareth like a bald-headed man" and like its family, flowers of Senecio vulgaris are succeeded by downy globed heads of seed. The seeds are achene, include a pappus[6] and become sticky when wet.[7] Laboratory tests have suggested maximum seed scattering distances of 4.2and at wind speeds of 6.8and respectively (affected by plant height), suggesting that it was more than wind that spread these groundsel seeds throughout the world.

The average weight of 1000 seeds is 0.21 gram (2,200,000 seeds per pound) and experienced a 100% germination success before drying and storage and an 87% germination success after drying and 3 years of cool dry storage.[8] In simple models for seed emergence prediction, soil thermal time did not predict the timing and extent of seedling emergence as well as hydrothermal time[9] [10] (warm rain).

Roots

The root system consists of a shallow taproot. This plant spreads by reseeding itself.[4]

Groundsel acts as a host for the fungus that causes black root rot in peas, alfalfa, soybeans, carrots, tomatoes, red clover, peanuts, cucurbits, cotton, citrus, chickpeas, and several ornamental flowering plants; a list of flowering plants that can host their own fungus as well.

Etymology and naming

Binomial etymology

Common names

Distribution

Senecio vulgaris is considered to be native to Europe, northern Asia, and parts of North Africa. Its further distribution is less clear. The United States Department of Agriculture (USDA), Natural Resources Conservation Service Plants Profile Database[17] considers it to be native to all 50 of the United States of America, Canada, Greenland, Saint Pierre and Miquelon, the same USDA through the Germplasm Resources Information Network (GRIN)[18] considers it to be native only to parts of Afro-Eurasia. The Integrated Taxonomic Information System Organization (ITIS), a partnership among many United States federal government departments and agencies[19] states that the species has been introduced to the 50 United States,[20] and the online journal Flora of North America calls it "probably introduced" to areas north of Mexico.[21] Individual research groups claim it is not native to areas they oversee: Florida,[22] Washington,[23] Wisconsin,[24] Saskatchewan,[25] British Columbia,[26] Missouri.[27] The United States Geological Survey reports that common groundsel is exotic to all 50 states and all Canadian provinces with the exception of Georgia, Kentucky, Massachusetts, and Labrador.[28]

Ecology

Senecio vulgaris is a frost-resistant[29] deciduous annual plant that grows in disturbed sites, waste places, roadsides, gardens, nurseries, orchards, vineyards, landscaped areas, agricultural lands,[14] at altitudes up to 1600feet[29] and is, additionally, self-pollinating[14] producing 1,700 seeds per plant with three generations per year. Seeds are dispersed by wind and also cling to clothing and animal fur,[12] and as contaminates of commercially exchanged seeds; the distribution of this plant throughout the world has been difficult if not impossible to contain.

Herbivores

The seed of common groundsel is a good green food for canaries and finches and it is available all year round.[12]

Senecio vulgaris seed has been found in the droppings of sparrows, and seedlings have been raised from the excreta of various birds. Seed has also been found in cow manure.[12]

Some Lepidoptera species eat many of the Senecio;[29] additional studies via electrophysiological recordings have shown that the taste sensilla of the cinnabar moth larvae respond (get excited) specifically to the pyrrolizidine alkaloids, which all Senecio contain.[30]

Moths and caterpillars[14] [31]

The Senecio also are host to other insects:[14] [32] [33]

Beetles

Flies

Seed flies (Diptera: Muscoidea)

Gall flies (Diptera: Tephritidae):

and other insects that are not listed here.

The ragwort flea beetle and ragwort seed fly have been approved and released for Senecio control in California,[14] Australia[32] and elsewhere.

FungiMost Senecio, including S. squalidus are susceptible to rust and other fungus and mildews:[29] [33] [34]

Rust fungus Uredinales

White rust Peronosporales

Sac fungus Ascochyta, Pezizomycetes

Groundsel mildew Erysiphales

Powdery mildew Erysiphales

Black root rot Microascales

and other fungus that are not listed here.

Toxicity

In the United States, Senecio vulgaris has been listed as a noxious weed,[35] being both non-indigenous to most if not all of the Americas and having a reputation for being hepatotoxic to livestock[36] and to humans.[37] [38] [39]

Toxic versus medicinal

HumanAs a plant that is reported to be both poisonous for human ingestion and also medicinal; much of the contradiction can be found by closely reviewing the words that are used and the dose (amount) of the poisonous substance that is ingested to prove either claim. All species of the genus Senecio contain pyrrolizidine alkaloids (e.g., senecionine), a substance that when a human has chronic exposure[40] can cause irreversible liver damage.[13] [41]

Common groundsel as a medicinal herb does not seem to have been recommended very often since 1931, when it was recommended as a diaphoretic, an antiscorbutic, a purgative, a diuretic and an anthelmintic, which was a demotion as it was previously suggested for the expelling of gravel of the kidneys and reins by Pedanius Dioscorides in the 1st century, for use as poultices by John Gerard in the late 16th century and as a cure for epilepsy by Nicholas Culpeper in the 17th century.[13] More current information is contradictory about the dangers of the ingestion of groundsel. A heavily referenced paper from 1989 suggests that the response is immediate and gives pre-ambulatory care recommendations.[37] A Canadian poisonous plants information database references a paper from 1990 in presenting this prenatal warning: "In a case of prenatal exposure, a mother ingested tea containing an estimated 0.343 milligram of senecionine, resulting in fatal veno-occlusive disease in a newborn infant."[41] Information about the pyrrolizidine alkaloids, the substance present in Senecio vulgaris is much less contradictory and all warn of accumulation of the alkaloid.[42] [43] [44] [45]

Certain pyrrolizidine alkaloids are non-toxic precursors that are converted to toxic metabolites in the body in a process called toxification[46]

Botanist and noted authority on plant-lore Albert Roy Vickery quotes a 1991 account of the use of groundsel as a highly effective purge in the English county of Dorset:

Mr Joby House, who used to be at Hewood, told us that, for constipation, you boiled groundsel and lard and take that and you will shit through the eye of a needle. His sister Lucy had constipation so bad that when the doctor called in the morning he said Lucy would be dead by 5 o’clock. Mrs. House went to the gypsies (Mrs. Penfold)…and she told her how to cure her. The doctor came late in the day, and Lucy was running around; there was shit everywhere. The doctor had brought Lucy’s death certificate, but he was so mad he tore it up and put it in the fire.[47]

LivestockCarl Linnaeus is cited to have claimed that "goats and swine eat this common plant freely, cows being not partial to it and horses and sheep declining to touch it, but not only are caged birds fond of it (the seeds), but its leaves and seeds afford food for many of our wild species (rabbits were given as an example)."[13] More recent studies claim that the lethal amount that cattle or horses need to consume is 7% of their body weight (example: 50lb would need to be consumed by a cow weighing 700lb). Lesser amounts cause the liver to lose function but is not apparent until the animal is stressed (by new feed or location, pregnancy, a different toxin, etc.). Sheep and goats have rumen bacteria that detoxify the alkaloids and are able to consume twice their body weight of this and other species of genus Senecio.[48] [49] The alkaloids responsible are not destroyed by drying or by fermentation in silage.[12]

Introduced versus invasive

Introduced species become invasive when they compete with natives or with crops. Senecio vulgaris is not known to be a strong competitor but it has been known to reduce mint production.[50] There is evidence that it is not a strong invasive and sometimes protective of critically endangered native plants.[51]

The approximately 22mm long[52] pappus seeds of Senecio vulgaris, each plant capable of producing 25,000 or more seeds (1,700 seeds per plant are more likely) with three generations of the plant per year;[48] seeds that are widely dispersed by the wind,[53] have been identified as a contaminant of cereal and vegetable seeds[29] and a poison to some livestock; there is some inspiration to understand the growth stages and determine some control methods.

CultivationCultivation with the hand or tiller is a recommended method of controlling Senecio vulgaris from growing in gardens and planting fields; cultivate to a depth of 2inches. The plant does prefer to take root in disturbed soils, so cultivation rids new plants but also buries and stirs up new seeds so the cultivation needs to be repeated at 14-day intervals.[12] Seeds can still mature even when the plant has been killed;[36] seed from plants cut in flower had germination levels of 35%. Groundsel seed numbers increased in soil during a two-year set-aside left fallow but not when there was a sown grass cover. The weed cannot live on grazed, trampled or mowed sites.[12]
BiologicalThe pathogen rust fungus or Puccinia lagenophorae and the cinnabar moth (Tyria jacobaeae) have both been used and studied in an attempt to control infestation of Senecio vulgaris.[54] One study showed that rust fungus infected Senecio vulgaris survived and actually used more of the available soil nutrients.[55] The cinnabar moth eats groundsel between June and August, but the seeds germinate and the plant grows as soon as the ground is warm enough (and after a warm rain),[9] making this an insufficient control almost everywhere groundsel can be found.[48]
ChemicalHerbicides designed to control broadleaf plants are effective for controlling Senecio vulgaris in cereals and forage grasses but also will "control" broadleaf crops, such as mint, forage legumes,[50] strawberries,[56] carrots[57] and all other non-grass crops. There is also evidence that the plant develops an immunity to the chemical control.[58] [59]
OtherGroundsel seedlings with 2–6 leaves are tolerant of flame weeding but the seeds are susceptible to soil solarization.[29]

See also

Further reading

External links

Notes and References

  1. Book: Stace, C. A.. Stace, C. A.. 2010. New Flora of the British Isles. Third. Cambridge University Press. Cambridge, U.K.. 9780521707725.
  2. Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press.
  3. Web site: Senecio vulgaris L. . 2008-02-05 . Dan Tenaglia . 2007-02-08 . Missouri Botanical Garden Press . 2012-06-27 . https://web.archive.org/web/20120627073613/http://www.missouriplants.com/Yellowalt/Senecio_vulgaris_page.html . dead .
  4. Web site: Common Groundsel (Senecio vulgaris) . 2008-02-07 . John Hilty . Illinois Wildflowers.
  5. Kim. M.. Cui, M.-L.. Cubas, P.. Gillies, A.. Lee, K.. Chapman, M. A.. Abbott, R. J.. Coen, E.. Regulatory Genes Control a Key Morphological and Ecological Trait Transferred Between Species. Science. 2008. 322. 5904. 1116–1119. 10.1126/science.1164371. 19008450. 2008Sci...322.1116K. 206515573.
  6. Web site: Ontario Weeds: Common groundsel . 2008-02-07 . OMAFRA Staff . Ministry of Agriculture, Food and Rural Affairs (Ontario) . 2002-06-01 . Publication 505, Ontario Weeds . Government of Ontario, Canada.
  7. Volunteer vascular plant establishment on roofs at the University of Saskatchewan . O.W. Archibold . L. Wagner . 2005-01-03 . Landscape and Urban Planning . . 20–28 . 10.1016/j.landurbplan.2006.03.001 . The seeds of two species, thyme leaved spurge (Euphorbia glyptosperma) and groundsel (Senecio vulgaris), become sticky when wet and two others, ... . 79.
  8. Web site: Search Results Senecio vulgaris . 2008-02-01 . Royal Botanic Gardens, Kew . Royal Botanic Gardens, Kew . Seed Information Database . Board of Trustees of the Royal Botanic Gardens, Kew.
  9. Emergence Prediction of Common Groundsel (Senecio vulgaris) . Milt McGiffen . Kurt Spokas . Frank Forcella . David Archer . Steven Poppe . Rodrigo Figueroa . amp . March 2007 . BioOne . 58–65 . 10.1614/WS-07-060.1 . 56 . Weed Science. 55715042.
  10. Common Groundsel (Senecio vulgaris) Seed Longevity and Seedling Emergence . Rodrigo Figueroa . Douglas Doohan . John Cardina . Kent Harrison . amp . July 2006 . BioOne . 187–192 . 10.1614/WS-06-122R1.1 . 55 . 3. Weed Science. 85776440.
  11. Gledhill, David (2008). "The Names of Plants". Cambridge University Press. (hardback), (paperback). pp 349, 404
  12. Web site: Groundsel . 2008-02-05 . Henry Doubleday Research Association . Henry Doubleday Research Association . October 2007 . Organic Weed Management . Garden Organic . 2007-10-27 . https://web.archive.org/web/20071027183817/http://www.gardenorganic.org.uk/organicweeds/weed_information/weed.php?id=41 . dead .
  13. Web site: Groundsel, Common . 2008-02-02 . M. Grieve . Maud Grieve . 1931 . A Modern Herbal . © Copyright Protected 1995-2008 Botanical.com.
  14. Web site: Genus Senecio . 2008-01-31 . California Department of Food and Agriculture . California Department of Food and Agriculture . Encycloweedia . State of California.
  15. Web site: Poisonous Plants: Senecio spp. . 2008-02-02 . Dr. Alice B. Russell, Department of Horticultural Science, North Carolina State University . 1997 . Poisonous Plants of North Carolina . https://web.archive.org/web/20071227105930/http://www.ces.ncsu.edu/depts/hort/consumer/poison/poison.htm . 2007-12-27 . dead.
  16. Book: Peterson Field Guide, Theodore F. Niehaus . Illustrations by Charles L. Ripper . Pacific States Wildflowers . 1976 . The Peterson Field Guide Series . Houghton Mifflin Company . New York . 0-395-91095-1 . 208 . 1976 .
  17. Web site: The Plants Database . 2008-02-01 . Natural Resources Conservation Service (NRCS) . Natural Resources Conservation Service . United States Department of Agriculture.
  18. Web site: National Plant Germplasm System . 2008-02-01 . Germplasm Resources Information Network (GRIN) . Germplasm Resources Information Network . 2007-10-29 . Germplasm Resources Information Network . USDA, ARS, National Genetic Resources Program, National Germplasm Resources Laboratory, Beltsville, Maryland.
  19. Web site: About ITIS . 2008-02-01 . Integrated Taxonomic Information System . Integrated Taxonomic Information System Organization (ITIS) . 2002-09-09 . Integrated Taxonomic Information System on-line database.
  20. Web site: Senecio vulgaris . 2008-01-29 . Integrated Taxonomic Information System . Integrated Taxonomic Information System Organization (ITIS) . 2007-12-20 . Integrated Taxonomic Information System on-line database.
  21. Web site: 37. Senecio vulgaris Linnaeus . 2008-02-01 . Flora of North America . Flora of North America . Vol. 20 Page 548, 562, 563.
  22. Web site: Senecio vulgaris L. . 2008-02-01 . Richard Wunderlin or Bruce Hansen . University of South Florida . 2006 . Atlas of Florida Vascular Plants . Institute for Systematic Botany.
  23. Web site: Asteraceae - Senecio: Senecio vulgaris . 2008-02-01 . Don Knoke . 2006 . Vascular Plants . Burke Museum of Natural History and Culture.
  24. Web site: Senecio vulgaris L. . 2008-02-01 . University of Wisconsin–Stevens Point . University of Wisconsin–Stevens Point . Robert W. Freckmann Herbarium.
  25. Web site: Common Groundsel . 2008-02-01 . Government of Saskatchewan . Politics of Saskatchewan . 2007 . Weed Identification Guide . dead . https://web.archive.org/web/20110706204053/http://www.agriculture.gov.sk.ca/Default.aspx?DN=a3e0e755-065f-4370-b6c5-df88957cb8f1 . 2011-07-06.
  26. Web site: Weeds of British Columbia Listed by Common Name . 2008-02-01 . Center for Biological Informatics of the U.S. Geological Survey . United States Geological Survey . dead . https://web.archive.org/web/20110721053233/http://export.nbii.gov/xml/web-resources/xmlfiles/ISN/56962.html . 2011-07-21.
  27. Web site: Flora of Missouri Senecio vulgaris Linnaeus . 2008-02-01 . Flora of North America . Flora of North America.
  28. Web site: Nature Serve Species Profile for Old-man-in-the-spring (Senecio vulgaris) . 2008-02-01 . United States Geological Survey . United States Geological Survey . 2006 . NatureServe . NatureServe’s Central Databases . Arlington, VA . dead . https://web.archive.org/web/20110721053301/http://export.nbii.gov/xml/natureserv/html/Asteraceae/1/ELEMENT_GLOBAL_2_161652.html . 2011-07-21.
  29. Web site: Groundsel (Senecio vulgaris) . 2008-02-05 . Hedgerowmobile . Species lists . Hedgerows, Hedges and Verges of Britain and Ireland.
  30. Gustatory responsiveness to pyrrolizidine alkaloids in the Senecio specialist, Tyria jacobaeae (Lepidoptera, Arctiidae) . E. A. Bernays . University of Arizona . T. Hartmann . R. F. Chapman . amp. March 2004 . Physiological Entomology . . 67–72 . 10.1111/j.1365-3032.2004.0366.x . 29 . 84528409.
  31. Web site: Biological Control of Ragwort (Senecio jacobaea L.) in Australia . 2008-02-20 . D. A. Mclaren . J. E. Ireson . R. M. Kwong . amp . 4–14 July 1999 . CRC for Weed Management Systems . X International Symposium on Biological Control of Weeds . 67–79 . "Its most common host is marsh ragwort (S. aquaticus).
  32. Web site: ragwort seed fly . 2008-02-20 . November 9, 2004 . Invasive and Exotic Species . The Bugwood Network.
  33. Web site: Senecio squalidus L. (Oxford Ragwort) . 2008-02-14 . BioImages: The Virtual Field-Guide (UK) . dead . https://web.archive.org/web/20080907222712/http://www.bioimages.org.uk/HTML/T606.HTM . 2008-09-07.
  34. Book: George Edward, Massee . George Edward Massee . Diseases of Cultivated Plants and Trees . 1915 . 2008-02-06 . 2007-07-10 . . 978-1-4067-8364-3 . 160.
  35. Web site: Washington State-listed Noxious Weeds . 2008-02-01 . Natural Resources Conservation Service (NRCS) . Natural Resources Conservation Service . Invasive and Noxious Weeds . United States Department of Agriculture.
  36. Web site: Common Groundsel IMPACT . 2008-02-01 . C. A. Wilen, University of California, Integrated Pest Management Program, San Diego County . University of California, Davis . 2006-05-23 . Pests in Gardens and Landscapes; Common Groundsel Management Guidelines . Statewide IPM Program, Agriculture and Natural Resources, University of California.
  37. Web site: Senecio vulgaris L. (PIM 484) . 2008-02-05 . A. Furtado Rahde . . September 1989 . Chemical Safety Information from Intergovernmental Organizations.
  38. Web site: Common Groundsel Senecio vulgaris . 2008-02-01 . Ministry of Agriculture and Lands . Agricultural Land Reserve . Weeds BC . . dead . https://web.archive.org/web/20071021101914/http://www.weedsbc.ca/weed_desc/com_ground.html . 2007-10-21.
  39. Web site: Cornell University answers questions about California Bay Area plants . 2008-02-01 . Cornell Poisonous Plants Database . Cornell University College of Agriculture and Life Sciences . 2008-01-16 . dead . https://web.archive.org/web/20030828065037/http://www.ansci.cornell.edu/cgi-bin/db2www/plfaq_frame.d2w/report2?num=17 . August 28, 2003.
  40. Web site: Chronic exposure . 2008-02-01 . GreenFacts . GreenFacts . GreenFacts Glossary.
  41. Web site: Notes on poisoning: Senecio vulgaris . 2008-02-02 . Government of Canada . Government of Canada . 2006-05-30 . Canadian poisonous plants . Canadian Biodiversity Information Facility.
  42. Web site: Bad Bug Book: Pyrrolizidine Alkaloids . 2008-02-05 . M. Walderhaug . January 1992 . . FDA/Center for Food Safety & Applied Nutrition.
  43. Web site: Safety issues affecting herbs: pyrrolizidine alkaloids . 2008-02-05 . Subhuti Dharmananda . Institute for Traditional Medicine, Portland, Oregon.
  44. 10415431 . Pyrrolizidine alkaloids in human diet. . Prakash AS . Pereira TN . Reilly PE . Seawright AA . 1999-07-15 . 443 . 1–2 . Mutat Res . 53–67 . 10.1016/s1383-5742(99)00010-1.
  45. Web site: Common Groundsel . 2017-07-13 . 2017 . Province of Manitoba.
  46. Web site: Pyrrolizidine Alkaloids . 2008-02-05 . Manuel Hernandez . 2004-02-23 . Poisonous Plants Homepage . Animal Science at Cornell University.
  47. Vickery, Roy, Oxford Dictionary of Plant Lore, pub. Oxford University Press 1995 ISBN 0-19-280053-1 entry 'Groundsel' pps. 163-4.
  48. Web site: Common Groundsel Senecio vulgaris L., PNW 466 . 2008-02-02 . Susan Aldrich-Markham . July 1994 . Pests in Gardens and Landscapes . . https://web.archive.org/web/20080120212354/http://extension.oregonstate.edu/catalog/html/pnw/pnw466/ . 2008-01-20 . dead.
  49. Comparison of hepatic in vitro metabolism of the pyrrolizidine alkaloid senecionine in sheep and cattle . Jennifer M. Duringer . Donald R. Buhler . A. Morrie Craig . November 2004 . American Journal of Veterinary Research . 65. 11. . 1563–1572 . 10.2460/ajvr.2004.65.1563. 15566096. free .
  50. Web site: Common Groundsel . 2008-02-03 . 2004 . Written Findings of the State Noxious Weed Control Board . Washington State's 2004 Noxious Weed list . dead . https://web.archive.org/web/20080723134434/http://www.nwcb.wa.gov/weed_info/Senecio_vulgaris.html . 2008-07-23.
  51. Web site: Endangered and Threatened Wildlife and Plants; Critical Habitat Designation for Sidalcea keckii (Keck's checkermallow) . 2008-02-03 . U.S. Fish and Wildlife Service . United States Fish and Wildlife Service . 2002-06-19 . Federal Register Online via GPO Access . . RIN 1018-AG93, Page 41669–41683 . dead . https://web.archive.org/web/20090514083355/http://www.fws.gov/policy/library/02fr41669.html . May 14, 2009.
  52. Web site: Senecio vulgaris . 2008-02-01 . . Seed ID Workshop . Ohio State University Cooperative extension service.
  53. Web site: Seed Exchange . 2008-02-05 . 2008-01-31 . A public access seed bank - established 1911 . J. L. Hudson, Seedsman.
  54. A fresh view on the control of the annual plant Senecio vulgaris . J. Frantzen . P. E. Hatcher . amp . 2004-11-24 . Integrated Pest Management Reviews . . 10.1023/A:1018436614685 . 2 . 2 . 77–85. 81106247.
  55. Web site: Nutrient Relations of Groundsel (Senecio vulgaris) Infected by Rust (Puccinia lagenophorae) at a Range of Nutrient Concentrations II. Uptake of N, P and K and Shoot-Root Interactions . https://web.archive.org/web/20071022063359/http://aob.oxfordjournals.org/cgi/content/abstract/61/4/499 . dead . 2007-10-22 . 2008-02-03 . N. D. Paul . P. G. Ayres . amp . 1987-11-09 . Annals of Botany Company . 61: 499–506, 1988.
  56. Web site: Reducing Common Groundsel in Strawberry Fields . 2008-02-03 . Leslie Huffman- Weed Management Specialist (Horticultural Crops)/OMAFRA . . dead . https://web.archive.org/web/20080830003215/http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2007/25hrt07a2.htm . 2008-08-30.
  57. Web site: Weeds and weed management in carrots - a review . 2008-02-03 . EWRS Working Group "Weed Management Systems in Vegetables", University of Perugia . 11th EWRS (European Weed Research Society) Symposium 1999, Basel . Facoltà di Agraria - Università degli Studi di Perugia.
  58. Triazine Resistance in Senecio vulgaris Parental and Nearly Isonuclear Backcrossed Biotypes Is Correlated with Reduced Productivity . 92 . 4 . William B. McCloskey and Jodie S. Holt . University of California, Riverside, Botany and Plant Sciences Department. University of California, Riverside . April 1990 . . . Vol. 92(4): pp. 954–962 . Isonuclear triazine-susceptible and triazine-resistant Senecio vulgaris L. biotypes were developed by making reciprocal crosses between susceptible and resistant biotypes..... 1062401 . 16667411 . 10.1104/pp.92.4.954.
  59. Web site: Comparison of Atrazine-Resistant and -Susceptible Biotypes of Senecio vulgaris L.: Effects of High and Low Temperatures on the in vivo Photosynthetic Electron Transfer in Intact Leaves . https://archive.today/20130415134759/http://jxb.oxfordjournals.org/cgi/content/abstract/40/8/849 . dead . 2013-04-15 . 2008-02-01 . Michel Havaux, Society for Experimental Biology, 2005 . 1989 . . . Volume 40, Number 8, Pp. 849–854 . The effects of temperature on the yield of in vivo modulated chlorophyll fluorescence were measured in intact leaves of atrazineresistant and -susceptible biotypes of the weed Senecio vulgaris L. .....

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