Xanthium strumarium
(common cocklebur)

Preferred Scientific Name

• Xanthium strumarium L. (1753)

Preferred Common Name

• common cocklebur

Other Scientific Names

• Xanthium abyssinicum Wallr.
• Xanthium brasilicum Velloso
• Xanthium californicum E.L. Greene
• Xanthium canadense Mill., 1768
• Xanthium canavillesii Schouw., 1849
• Xanthium chinense Mill.
• Xanthium echinatum Murray, 1784
• Xanthium indicum Klatt, 1880
• Xanthium italicum Moretti
• Xanthium macrocarpum DC
• Xanthium occidentale Bertol.
• Xanthium orientale L. 1763
• Xanthium pensylvanicum Wallr. 1844
• Xanthium pungens Wallr. 1844
• Xanthium ripicola
• Xanthium sibiricum Patrin ex Widder, 1923
• Xanthium strumarium var. canadense (Mill.) Torr. & A. Gray
• Xanthium varians Greene
• Xanthium vulgare Hill

International Common Names

• English: clotbur; cocklebur; ditchbur
• Spanish: Chayotillo
• French: lampourde glouteron
• Portuguese: bardana-menor

Local Common Names

• Australia: noogoora bur; sheep bur
• Germany: Stachel- Spitzklette
• India: adhisishi; bada gokhru bhakra; chota dhatura
• Italy: lappola comune
• Japan: onamomi
• Malaysia: buah anjang
• Netherlands: ongedoornde stekelnoot
• Pakistan: puth kando
• South Africa: kankerroos
• Taiwan: tsai-er
• Thailand: kachab
• Turkey: siraco out

EPPO code

• XANPU (Xanthium pungens)
• XANST (Xanthium strumarium)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Asterales
•                         Family: Asteraceae
•                             Genus: Xanthium
•                                 Species: Xanthium strumarium

The revised classification of Xanthium taxa by Love and Dansereau (1959) reduced the number of Xanthium species to two: X. strumarium and X. spinosum. The numerous species of Xanthium reported in the literature, other than X. spinosum, are now considered forms of X. strumarium. This is an extremely variable species comprising at least two subspecies (for example, X. strumarium var. canadense) and a group of complexes within each, differing in geographic distribution and bur morphology. There are no sterility barriers between subspecies or complexes (Love and Dansereau, 1959; McMillan, 1974; 1975). All these Xanthium taxa are tetraploid with a chromosome number of 2n = 36 (Love and Dansereau, 1959). The related species X. spinosum is more homogeneous throughout its range than X. strumarium. Hybrids between the two species can occur (Love, 1976).

X. strumarium is a coarse, erect, branching, annual herb which reproduces solely by seed; stems 30 to 150 cm tall, tough, with short dark streaks or spots and covered with short hairs which give a coarse texture; leaves alternate, triangular-ovate to broadly ovate in shape, 2 to 12 cm long, base often cordate, petiole 2 to 8 cm long, margins irregularly toothed or lobed, both surfaces rough-pubescent; flowers monoecious, male flowers inconspicuous, many-flowered heads 5 to 8 mm across, clustered at the tips of branches or axillaries above the female flowers, female flower heads axillary, greenish, two flowers in the head enclosed by the involucre; fruit, a hard brown, ovoid bur, 1.5 to 2.5 cm long, covered with hooked spines 2 to 4 mm long, and with two terminal beaks, fruits readily stick to clothing and fur, and thus are easily spread; seeds (achenes) black, two in each bur, one above the other (from Holm et al., 1977).

Category	Sub-Category	Habitat	Presence	Status
Terrestrial

X. strumarium is a major weed of row crops such as soyabeans, cotton, maize and groundnuts in many parts of the world, including North America, southern Europe, the Middle East, South Africa, India and Japan. In 1995, it ranked as the fourth, fifth, sixth and seventh most troublesome weed in soyabean, cotton, maize and groundnut, respectively, across 10 southern states in the USA. Between 1974 and 1995, X. strumarium decreased in importance in maize, soyabean and groundnuts in the southern USA, but increased in cotton (Webster and Coble, 1997). These rankings were based on distribution, abundance and difficulty of control.

In soyabeans, cocklebur has been reported to cause the highest reductions in yield of all annual weeds in both northern and southern production areas of the USA (Stoller et al., 1987). Soyabean yield losses are estimated at 10 to 16% for 0.5 plants of X. strumarium per m of row, 65% for 4 plants and 80% for over 10 plants per m of row, for weeds emerging at the same time as the crop (Stoller et al., 1987; Rushing and Oliver, 1998). Similar yield losses from cocklebur were reported in Ontario, Canada (Weaver, 1991). In Italy, Sartorato et al. (1996) recommended an economic threshold of only 0.05 plants of X. strumarium per square m in soyabeans. In addition to direct yield losses through competition, infestations of X. strumarium decrease soyabean seed quality and harvesting efficiency. One cocklebur per m of row was shown to cause a 7.2% increase in foreign material in harvested soyabeans, a 5.2% increase in seed moisture content, decreased test weight by 58.6 g/L seed, and reduced combine speed (Ellis et al., 1998). The authors recommended use of a pre-harvest desiccant when cocklebur densities exceeded 0.5 plants per m of row.

In cotton in the USA, seed yield losses of 60 to 90 kg/ha (approximately 5%) have been reported from cocklebur growing at a density of one plant per 15 m of row in Mississippi (Snipes et al., 1982). Cotton yield losses from one plant of X. strumarium per 3 m of row varied from 6 to 27% in North Carolina (Byrd and Coble, 1991). The critical period for cocklebur in cotton lasted from 2 to 10 weeks after cotton emergence (Snipes et al., 1987).

In groundnuts, cocklebur has been reported to cause yield losses of 31-39% at a density of 0.5 plants and 88% at 4 plants per m of row in the southern USA (Royal et al., 1997a, b). Cocklebur densities higher than 1 plant per 2 m of row reduced deposition of the fungicide chlorothalonil by 34% (Royal et al., 1997b).

The economic impact of X. strumarium in maize is somewhat lower than for soyabeans, cotton and groundnuts. Yields of maize in Illinois, USA have been reported to decrease by 10% at 1 cocklebur per m of row, to a maximum yield loss of 27% at a density of 4.7 cockleburs per m of row (Becket et al., 1988).

Infestations of X. strumarium can also cause significant yield losses in horticultural row crops (Weaver and Lechowicz, 1983). In snap beans, yield losses of 5 to 50% were reported for densities of X. strumarium ranging from 0.5 to 8 per square m (Neary and Majek, 1990).

X. strumarium also has a detrimental impact on livestock production which has been best documented in Australia, where it is abundant in sheep-grazing regions in the eastern half of the continent in Queensland and New South Wales (Wapshere, 1974; Hocking and Liddle, 1986). The burs lodge in animal hair and sheep wool, and are difficult to remove when the wool is processed after shearing. Contaminated wool requires special treatment and may have a price penalty of 25% or more (Wapshere, 1974). The prickly burs can cause considerable discomfort to animals by clinging to hair on the legs and matting the tails and manes of horses.

X. strumarium also has an economic impact in pastures, where cattle, sheep and pigs may be poisoned by eating young plants. The cotyledons contain a toxic compound, carboxyatractyloside, which is absent in older plants (Weaver and Lechowicz, 1982; Hocking and Liddle, 1986; Martin et al., 1992). Symptoms include vomiting, muscular spasms, liver degeneration and occasionally death.

Cocklebur serves as a host for a number of pathogens of crops. Sunflowers have been reported to be damaged by the rust Puccinia xanthii, commonly found on cocklebur, and by alternaria leaf spot (Alternaria helianthi), also found on cocklebur in North America (Hocking and Liddle, 1986). Cocklebur is reported to be a host for Sclerotinia minor and S. sclerotiorum which contaminate soyabean and discolour seed and result in a lowered price (Hocking and Liddle, 1986). X. strumarium is also an alternate host for the insect Spilosoma obliqua (Lepidoptera) which attacks Egyptian clover in India (Dhaliwal, 1993), and for Colletotrichum capsici, which causes anthracnose on tomato fruit and cotton seedlings in the USA (Mclean and Roy, 1991).

The Xanthium genus is closely related to the Ambrosia (ragweed) genus, and X. strumarium produces large amounts of highly antigenic pollen (Reddi et al., 1980). The glandular hairs on the leaves and stem secrete a substance which causes contact dermititis in allergic individuals (King, 1966).

Impact mechanisms

• Competition (unspecified)

X. strumarium, has been used for various medicinal purposes, including the treatment of malaria in India (Mitich, 1987; Talakal et al., 1995). The genus name is derived from the Greek root 'Xanthos' which means 'yellow', and the plant may once have been used to produce a dye (Weaver and Lechowicz, 1982).