Herbivore Defenses of Senecio viscosus L.
Sticky groundsel, Senecio viscosus, is rare in the Ottawa area. According to Gray's
Manual of Botany, a major environmental niche for it on this continent is railway ballast, and
that's where I almost always find it here. Its fine roots wind over stone surfaces, apparently to
scavenge moisture that condenses between the stones most nights. Its leaves are succulent to
store water. A specimen that I collected had no visible soil at all on its roots. Yet, after planting
in my garden, it continued to develop buds, bloom, and set seed as if nothing had ever disturbed
The compound that makes its leaves sticky (and scented; people who don't like plants call it
stinking groundsel!) is a pesticide - it helps to defend the plant against herbivores. Grazing
animals are pests to plants, after all, and the leaves of most Senecio species contain
chemicals which can kill most insects and grazing animals in a single meal. However, caterpillars
of the genus Tyria actually seek out Senecio. They store the chemicals
in their bodies, presumably to make them in turn unpalatable to their own predators. The hairs of
sticky groundsel, however, exude an additional compound, which specifically deters
Tyria caterpillars. The strategy seems to be successful here, for there was no visible
insect damage to any of the plants I found.
Sticky groundsel seems to require something very specific (and obscure) to produce its defensive
chemicals. My specimen produced 43 blooms, with an average of 52 seeds per seed head. Each
seed has a gossamer-fine cone of 6mm hairs that catches the slightest breeze. There is nothing I
can discern about the roadbed where it grew that differs from other parts of the adjacent 10km of
groundsel-free roadbed that I have walked. The same puzzlement was expressed by Cole, who
reported the first known occurrence of this plant in the Ottawa District (Trail & Landscape
Senecio viscosus is a fascinating little plant, that raises all sorts of natural
questions. Are pesticides such as it produces really as much less common in land plants than in
coral reefs as literature indicates? Or, perhaps, have people had blinkers on with regard to such
questions? Nature may be green in 'tooth and claw' too, not just red!
The stages of bloom: bud, fertile flower daytime, fertile flower nightime, fertilized flower,
mature flower, seed dispersal day 2, seed dispersal day 4, airborne seed, remaining bracts morning,
remaining bracts evening
Reference notes: (BA references are Biological Abstracts)
- Adamson 1900 "Horse sickness, a disease particular to South Africa, is doing its work;
a horse starts out perfectly well and is dead by noon." (quoted in "The Private
Capital", Gwyn, pg.360) Senecio poisoning of horses unaccustomed to the veld was a major
difficulty for the British during the Boer war.
- Hendrik 1928 BA5:7947 Cattle poisoning by S.
- van Es 1929 BA5:15080 S. & 'walking disease' of horses. 85 refs.
- Manske 1939 Cdn.J.Res.B17:1-9 occurence of Senecio alkaloids
- de Waal 1941 BA18:3448 18 S. alkaloids are known.
- Harris 1942 J.Pharm & Expt.Therapy 75:69-88 lethal doses and effects of S. alkaloids.
Most cause cell haemorrhage of various types.
- Manske 1944 Ann.Rev.Biochem 1944:533 review of S. alkaloids
- Warren 1948- J.Chem.Soc.London "The Senecio Alkaloids" 1948:1891-1982;
1949:486-487; 1949:1700-1703; 1949:1703-1705; 1949:2852-2854; 1950:700-702;
1950:702-703; 1951:66-68; 1952:3445-3448; 1955:59-63; 1955:63-65; 1955:65-67;
1958:4574-4575; 1962:34-37; 1963:953-956; 1964:4974-4978; 1968C:781-782.
- Sapeika 1952 South African Medical Journal 26:485:488 medical effects of S. alkaloids.
S.viscosus contains only senecionine. S. poisoning is 'Pictou disease' in Nova Scotia. The LD50
of S.alkaloids ranges from 58 to 830mg/kg, 44 references.
- Segerstad 1953 BA28:29403 S.viscosus invasion of Scandinavia (Swedish).
- Areshkina 1957 BA34:14470 S. alkaloid accumulation associated with plant enzyme
- Chapman 1974 Bulletin of Entomological Research 64:339-363 Tyria jacobaea (cinnabar
moth) caterpillars eat all S.sp. except S.viscosus, storing the pyrrolizadine N-oxides in its body.
The sticky hairs of S.viscosus contain something additional which can be dissolved off in methyl
alcohol, making the S.viscosus appetizing for T.j., and transferred to another plant, making it
- von Borstel 1986 Plant Cell Reports 5:39-42 Alkaloids, particularly N-oxides of
pyrrolizadine are produced in all S.sp., resulting in liver carcinomas in livestock. S.viscosus
contains a specific membrane carrier for this alkaloid. It is believed to inhibit insect herbivores,
but few experiments have been done.
- Blanchard 1944 BA19:11839 Aphis senecionicoides found; Macrosiphum capitophoroides
on S.sp., Argentine.
- Bourquin 1942 BA16:21331 Eurota hermione feeds on S.sp. in Argentina.
- Collart 1934 BA10:19917 Chortophila seneciella found on S.jacobaea; Belgium.
- Germain 1934 BA10:17194 Marconia jeanneli found on arborescent S.sp.
- Gillette 1929 BA5:18994 Aphidini senecioradicus live on S. roots.
- Meijere 1934 BA10:14829 Dizygomyza sp. larvae found on S.doria; Spain.
- Melis 1933 BA10:7406 Melanthrips inflativentris found on S.doria; Spain.
- Michener 1936 BA11:15223 Ashmeadiella florissantensis found on S.sp.; Colorado.
- Miller 1940 Bull.Imp.Bur.Past.&For.Crops Herb.Publ.27 BA15:13332 Biological
control of New Zealand Senecios by seed-infesting insects.
- Munro 1929 BA9:4120 S.sp. are hosts to some fruit flies.
- Priesner 1933 BA8:16954 Haplothrips setiger & Statice pectinata found on S.sp.
- Savulescu 1943 BA22:7157 Aecidum senecionis found on S.macrophyllus.
- Scott 1935 BA10:7263 Mnionomus jeanneli & M.alluaudi found on S.keniodendron;
Micrambe senecionis on S.sp.; Atheta suprema on S.adnivalis & S.erioneuron; all arboreal
sp. east Africa.
- Tilden 1953 BA28:19592 S. is a common host of Trirhabda flavolimbata, California.
- Lambert 1979 Physiologia Plantarum 46:194-202 There are 3 oxygen-using mechanisms in
roots, one for synthesis of shoots, a cyanide-resistant alternative electron-transport chain
(Solomos 1977), and a third one of unknown origin; the latter two are 'wasteful'. S.viscosus has a
high oxygen requirement for shoot synthesis. Excess sugar in root cells decreases their
permeability to water. S.viscosus is intolerant of flooding (ibid 43:277-281 & 42:163-166).
- Sheldon 1973 New Phytologist 72:665-675 The terminal velocity of Cirsium arvense seeds
is .22, S.viscosus .32, Taraxacum officinale .36m/s.
other notes on nature studies