Invasive Species Compendium

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Datasheet

Bidens pilosa
(blackjack)

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Datasheet

Bidens pilosa (blackjack)

Summary

  • Last modified
  • 14 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Bidens pilosa
  • Preferred Common Name
  • blackjack
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae

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Pictures

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PictureTitleCaptionCopyright
Bidens pilosa, flowers and fruit.
TitleFlowers and fruit
CaptionBidens pilosa, flowers and fruit.
Copyright©Chris Parker/Bristol, UK
Bidens pilosa, flowers and fruit.
Flowers and fruitBidens pilosa, flowers and fruit.©Chris Parker/Bristol, UK
B. pilosa seedlings have lanceolate cotyledons. The first true leaf is similar to later leaves.
TitleSeedling
CaptionB. pilosa seedlings have lanceolate cotyledons. The first true leaf is similar to later leaves.
CopyrightEduardo Leguizamon
B. pilosa seedlings have lanceolate cotyledons. The first true leaf is similar to later leaves.
SeedlingB. pilosa seedlings have lanceolate cotyledons. The first true leaf is similar to later leaves. Eduardo Leguizamon
Emerging seedlings of B. pilosa in the field.
TitleEmerging seedlings
CaptionEmerging seedlings of B. pilosa in the field.
Copyright©S.D. Sawant
Emerging seedlings of B. pilosa in the field.
Emerging seedlingsEmerging seedlings of B. pilosa in the field.©S.D. Sawant
Herbaceous, erect plant 20-150 cm tall, depending on growing conditions.
TitleGrowth habit
CaptionHerbaceous, erect plant 20-150 cm tall, depending on growing conditions.
Copyright©S.D. Sawant
Herbaceous, erect plant 20-150 cm tall, depending on growing conditions.
Growth habitHerbaceous, erect plant 20-150 cm tall, depending on growing conditions.©S.D. Sawant
Stems erect, square, glabrous or minutely hairy. Dark green, opposite leaves on stems and branches, 4-20 cm long, pinnate (or pinnatifid) with 2-3 pairs of pinnae and a single terminal leaflet.
TitleMature stems
CaptionStems erect, square, glabrous or minutely hairy. Dark green, opposite leaves on stems and branches, 4-20 cm long, pinnate (or pinnatifid) with 2-3 pairs of pinnae and a single terminal leaflet.
CopyrightEduardo Leguizamon
Stems erect, square, glabrous or minutely hairy. Dark green, opposite leaves on stems and branches, 4-20 cm long, pinnate (or pinnatifid) with 2-3 pairs of pinnae and a single terminal leaflet.
Mature stemsStems erect, square, glabrous or minutely hairy. Dark green, opposite leaves on stems and branches, 4-20 cm long, pinnate (or pinnatifid) with 2-3 pairs of pinnae and a single terminal leaflet.Eduardo Leguizamon
Achenes or seeds linear, black or dark brown, sparsely hairy. Pappus with 2-3 yellowish barbed awns which aid dispersal as they readily attach to animal skin, machinery or clothing.
TitleSeeds
CaptionAchenes or seeds linear, black or dark brown, sparsely hairy. Pappus with 2-3 yellowish barbed awns which aid dispersal as they readily attach to animal skin, machinery or clothing.
Copyright©S.D. Sawant
Achenes or seeds linear, black or dark brown, sparsely hairy. Pappus with 2-3 yellowish barbed awns which aid dispersal as they readily attach to animal skin, machinery or clothing.
SeedsAchenes or seeds linear, black or dark brown, sparsely hairy. Pappus with 2-3 yellowish barbed awns which aid dispersal as they readily attach to animal skin, machinery or clothing.©S.D. Sawant

Identity

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Preferred Scientific Name

  • Bidens pilosa L.

Preferred Common Name

  • blackjack

Other Scientific Names

  • Bidens alausensis Kunth
  • Bidens chilensis DC.
  • Bidens leucantha (L.) Willd.
  • Bidens scandicina Kunth
  • Coreopsis leucantha L.

International Common Names

  • English: beggar tick; bur marigold; cobbler's pegs; duppy needles; farmer's friend; needle grass; spanish needle; stick tight
  • Spanish: apestosa (Honduras); chipaca (Colombia); jacalate (Spain); manzanilla del pais (Bolivia); papuga; picon; romerillo blanco (Cuba); rosilla grande (Honduras); vara de jacalate (Spain)
  • French: piquant noirs
  • Chinese: hsien-feng-tsau; xiang feng cao
  • Portuguese: amor-de-burro

Local Common Names

  • Angola: olokosso
  • Argentina: amor seco; espina de erizo; picón; saetilla
  • Australia: cobbler's pegs
  • Barbados: spanish needle
  • Brazil: amor seco; carrapicho-de-duas pontas; coambi; erva-picao; fura-capa; goambu; picao; picao preto; picao-campo; pico-pico
  • Chile: asta de cabra; cacho de cabra
  • Colombia: cadillo; masquia; papunga chipaca
  • Comoros: mtsohova; sindanou
  • Cook Islands: piripiri
  • Dominican Republic: margarita silvestre; romerillo
  • Fiji: batimadramadra; matakaro; matua kamate; mbatikalawau; mbatimandramandra
  • Germany: Zweizahn, Behaarter
  • India: cobbler's pegs; dipmal; phutium
  • Indonesia: adjeran harenga; djaringan ketul
  • Jamaica: spanish needle
  • Japan: ko-sendangusa
  • Kenya: blackjack
  • Laos: pak kwan cham
  • Mauritius: herbe villebague
  • Mexico: acahual; acahual blanco; aceitilla; aceitilla blanco; aceitillo; amapola; amor seco; cadillo; China; cruceta; é de milpa; hierba amarilla; hierba del pollo; iztacmozot; kutsúmu (purépecha); mozoquelite; mozote; mozote blanco; mozotl; quelite amargo blanco; rocía; rocilla; rosilla; saetilla; sepé; sepeke (tarahumara); stuyut; té de milpa blanco; te de playa; tutuk joi'dha (tepehuán); zetya
  • Myanmar: moat-so-ma-hlan; ne-gya-gale; ta-se-urt
  • New Caledonia: piquant noirs
  • New Zealand: cobbler's pegs
  • Niue: kofe tonga; kofetoga
  • Northern Mariana Islands: beggar ticks; Guam daisy
  • Panama: arponcito; cadillo; sirvulaca
  • Papua New Guinea: kobkob
  • Peru: amor seco; cadilla; pega-pega; perca
  • Philippines: dadayem; nguad; panibat; pisau-pisau; puriket; purpurikit; tagab; tubak-tubak
  • Puerto Rico: margarita; margarita silvestre; romerillo
  • Saudi Arabia: piquant; sornette zerb lapin
  • South Africa: blackjack; gewone knapseherel
  • Taiwan: hsien-feng-tsau
  • Thailand: puen nok sai; yah koen-jam khao
  • Tonga: fisi'uli
  • Trinidad and Tobago: railway daisy; spanish needle
  • Uruguay: amor seco
  • USA: beggar ticks; hairy beggarticks; spanish needles
  • USA/Hawaii: ki; ki nehe; ki pipili; kookoolau; nehe; pilipili
  • Venezuela: cadillo rocero
  • Vietnam: cuc trang; su nha long
  • Zambia: blackjack
  • Zimbabwe: nyamaradza

EPPO code

  • BIDCH (Bidens chilensis)
  • BIDPI (Bidens pilosa)
  • CRLLE (Coreopsis leucantha)

Taxonomic Tree

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

Notes on Taxonomy and Nomenclature

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Carolus Linnaeus (1701–1778) described the genus in Species Plantarum, 1753, and Genera Plantarum, 1754. Bidens is a taxonomically difficult genus of more than 230 species according to Sherff (1937) but Wagner et al. (1999) note that many of these do not deserve recognition. The name, Bidens, is derived from the Latin bi, two, and dens, teeth, referring to the prominent barbed awns projecting from the apex of each seed. The specific epithet, pilosa, refers to the downy hairs on the stems and the leaves (Pope, 1968).

Ballard (1986) has described the 'B. pilosa complex' with its centre of diversification in Mexico. On the basis of field observations, chromosome counts, flavonoid chemistry, breeding system, hybridization experiments and quantitative analysis of morphological features, he described three distinct species: B. odorata (n = 12), B. alba (n = 24) and B. pilosa (n = 36). B. odorata and B. alba occur mainly in Central and South America, while it is typical B. pilosa, which is the most widespread as a weed. The chromosome number of nine B. pilosa populations from Brazil was 2n = 48, 70 and 72 (Mariano and Marin Morales, 1998). According to Wagner et al. (1999), the chromosome number of B. pilosa is 2n = 24, 36, 46, 48, 72 and ca 76.

A number of varieties of B. pilosa have also been described, though not universally accepted. One referred to in the weed literature, B. pilosa var. radiata, may more correctly be referred to B. alba. Most of the information in this data sheet is believed to relate to B. pilosa sensu stricto.

Description

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B. pilosa seedlings have lanceolate (strap-shaped) cotyledons, 25 mm long, and purple-tinged hypocotyls. The first true leaf is similar to later leaves. Finot et al. (1996) describe the morphology of dry seed, unfolded cotyledons, first true leaf or leaf pair unfolded and two to five true leaves unfolded. Original drawings and photographs accompany each description.

The plant is an erect annual herb, 20–150 cm tall (in tall plants sometimes the branches straggling), very variable, reproducing by seeds. Main root pivotant. Stems square, glabrous or minutely hairy, green or with brown strips. Dark green, opposite leaves on stems and branches, 4–20 cm long, up to 6 cm wide, the lower leaves simple, ovate and serrate, the upper leaves trifoliolate or imparipinnate with 2–3 pairs of pinnae and a single terminal leaflet. Petioles are 2–5 cm long.

The inflorescence is an isolated or grouped pedunculated capitula, emerging from the leaf axil. Heads borne singly at the ends of long, slender, nearly leafless branches; narrow, discoid, the disk 4-6 mm wide at anthesis; ray florets, absent or 4–7 per head, white or pale-yellow, 2–8 mm long, disk florets, 35–75 per head, yellow.

Achenes (commonly referred to as 'seeds') linear, black or dark brown, 1–1.5 cm long, flat, 4-angled, sparsely hairy. Pappus with 2–3(–5) yellowish barbed awns, 1–2 mm long. The achenes are the dispersal units; dispersion is aided by the awns as they readily attach to animal skin, machinery and clothing.

Distribution

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B. pilosa is native to tropical America but is now a pantropical weed (Wagner et al., 1999). Latin America and eastern Africa have the worst infestations of the weed (Mitich, 1994). It can usually be seen in all seasons in the tropics but it grows most actively in the warmer and wetter parts of the seasons (Holm et al., 1977). It is of major to intermediate importance as a weed in crops, pastures, wastelands, gardens, cultivated areas and on roadsides (Galinato et al., 1999).

It is increasingly being cultivated as an indigenous leafy vegetable (ILV), mainly in southern Africa.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

AfghanistanPresentHolm et al., 1979
BangladeshPresentSudha et al., 1998
CambodiaPresentWaterhouse, 1993
ChinaPresentHolm et al., 1979
-Hong KongPresentHolm et al., 1979
Christmas Island (Indian Ocean)PresentUSDA Forest Service, 2000
IndiaPresentMoody, 1989; Singh et al., 1992
-MeghalayaPresentSahay et al., 1999
-Uttar PradeshPresentSingh, 2010
IndonesiaPresentTjitrosemito, 1987; Moody, 1989; Waterhouse, 1993
JapanPresentIshimine et al., 1986
LaosPresentWaterhouse, 1993
MalaysiaPresentWaterhouse, 1993
MyanmarPresentWaterhouse, 1993
PhilippinesPresentMoody, 1989; Waterhouse, 1993; Zulueta et al., 1995
TaiwanPresentGuo and Lin, 1986
ThailandPresentMoody, 1989; Waterhouse, 1993
VietnamPresentWaterhouse, 1993

Africa

AngolaPresentHolm et al., 1979
BotswanaPresentKarikari et al., 2000
Burkina FasoPresentTraore and Maillet, 1998
CameroonPresentHolm et al., 1979
CongoPresentHolm et al., 1979
Côte d'IvoirePresentHolm et al., 1979
EgyptPresentAbd El Ghani, 1998
EthiopiaPresentSahile et al., 1992
GhanaWidespreadHolm et al., 1979
GuineaPresentHolm et al., 1979
KenyaWidespreadHolm et al., 1979
LiberiaPresentHolm et al., 1979
MaliPresentHolm et al., 1979
MauritiusWidespreadHolm et al., 1979
MozambiqueWidespreadHolm et al., 1979
NigerPresentHolm et al., 1979
SenegalPresentHolm et al., 1979
South AfricaPresentFenner, 1980; Forsyth and Brown, 1982
SwazilandWidespreadHolm et al., 1979
TanzaniaPresentChhabra et al., 1993
UgandaPresentKatende, 1983
ZambiaWidespreadHolm et al., 1979
ZimbabweWidespreadHolm et al., 1979

North America

CanadaPresentHudson et al., 1986
MexicoPresentOcampo-Ruiz et al., 1990; Holm et al., 1979
USAPresentReddy and Singh, 1992; Mitich, 1994
-AlabamaPresentUSDA-NRCS, 2001
-ArizonaPresentUSDA-NRCS, 2001
-CaliforniaPresentUSDA-NRCS, 2001
-ConnecticutPresentUSDA-NRCS, 2001
-FloridaPresentUSDA-NRCS, 2001
-GeorgiaPresentUSDA-NRCS, 2001
-HawaiiWidespreadHolm et al., 1979
-KentuckyPresentUSDA-NRCS, 2001
-LouisianaPresentUSDA-NRCS, 2001
-MarylandPresentUSDA-NRCS, 2001
-MassachusettsPresentUSDA-NRCS, 2001
-MississippiPresentUSDA-NRCS, 2001
-New MexicoPresentUSDA-NRCS, 2001
-North CarolinaPresentUSDA-NRCS, 2001
-PennsylvaniaPresentUSDA-NRCS, 2001
-South CarolinaPresentUSDA-NRCS, 2001
-TexasPresentUSDA-NRCS, 2001
-WisconsinPresentUSDA-NRCS, 2001

Central America and Caribbean

Costa RicaPresentInostrosa and Fournier, 1982
CubaPresentHudson et al., 1986
Dominican RepublicPresentHolm et al., 1979
El SalvadorPresentHolm et al., 1979
HondurasPresentHolm et al., 1979
JamaicaPresentHolm et al., 1979
Lesser AntillesPresentHolm et al., 1979
NicaraguaPresentSalomon, 1990; Otabbong et al., 1991
PanamaPresentHolm et al., 1979
Puerto RicoWidespreadHolm et al., 1979
Trinidad and TobagoWidespreadHolm et al., 1979
United States Virgin IslandsPresentUSDA-NRCS, 2001

South America

ArgentinaPresentFrancescangeli and Mitidieri, 1990
BoliviaWidespreadHolm et al., 1979
BrazilPresentKissman & Groth, 1993; Fleck et al., 1989
-Mato GrossoPresentSanchez and Zandonade, 1997
-Mato Grosso do SulPresentSanchez and Zandonade, 1997
-Minas GeraisPresentLaca Buendia et al., 1999
-ParaibaPresentVieira et al., 1998a; Vieira et al., 1998b
-ParanaPresentAndrade et al., 1999
-Sao PauloPresentPaulo et al., 1997; Fonseca et al., 1999
ChilePresentPrado and Nitsche, 1989
ColombiaPresentMontenegro-Galvez and Criollo Escobar, 1978
EcuadorPresentPresent based on regional distribution.
-Galapagos IslandsPresentUSDA Forest Service, 2000
French GuianaPresentMori and Brown, 1998
PeruPresentBazan and Ochea, 1974; Cerna and Valdez, 1987
UruguayPresentHolm et al., 1979
VenezuelaWidespreadHolm et al., 1979

Europe

FrancePresentN'Dounga et al., 1983

Oceania

American SamoaPresentUSDA Forest Service, 2000
AustraliaPresentHolm et al., 1979
-Australian Northern TerritoryPresentBenson and McDougall, 1994
-Lord Howe Is.PresentUSDA Forest Service, 2000
-New South WalesPresentAgriculture Western Australia, 2000
-QueenslandPresentHenderson, 2000
-South AustraliaPresentBenson and McDougall, 1994
-VictoriaPresentBenson and McDougall, 1994
-Western AustraliaPresentAgriculture Western Australia, 2000
Cook IslandsPresentWaterhouse, 1997
FijiPresentHolm et al., 1979
French PolynesiaPresentWaterhouse, 1997
GuamPresentUSDA Forest Service, 2000
KiribatiPresentUSDA Forest Service, 2000
Marshall IslandsPresentUSDA Forest Service, 2000
Micronesia, Federated states ofPresentUSDA Forest Service, 2000
NauruPresentUSDA Forest Service, 2000
New CaledoniaPresentWaterhouse, 1997
New ZealandPresentHolm et al., 1979
-Kermadec IslandsPresentUSDA Forest Service, 2000
NiuePresentUSDA Forest Service, 2000
Norfolk IslandPresentGreen, 1994
Northern Mariana IslandsPresentSeaver, 2000
PalauPresentUSDA Forest Service, 2000
Papua New GuineaWidespreadHolm et al., 1979
Pitcairn IslandPresentUSDA Forest Service, 2000
SamoaPresentWaterhouse, 1997
Solomon IslandsPresentWaterhouse, 1997
TongaPresentWaterhouse, 1997
VanuatuPresentWaterhouse, 1997
Wallis and Futuna IslandsPresentUSDA Forest Service, 2000

Hosts/Species Affected

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B. pilosa is troublesome in both field and plantation crops and is reported to be a weed of 31 crops in more than 40 countries (Holm et al., 1977).

It is regarded as a principal weed of sugarcane, maize, coffee, tea, cotton, potatoes, vegetables, bananas, beans and citrus in various Latin American and African countries (Holm et al., 1977) and a serious weed in many other situations. In upland rice in South and South-East Asia, it is common in Thailand and present in Indonesia, Laos, Myanmar, Philippines and Vietnam (Galinato et al., 1999).

Host Plants and Other Plants Affected

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Plant nameFamilyContext
Camellia sinensis (tea)TheaceaeMain
CitrusRutaceaeMain
Coffea (coffee)RubiaceaeMain
Glycine max (soyabean)FabaceaeMain
Gossypium (cotton)MalvaceaeMain
Musa (banana)MusaceaeMain
Phaseolus (beans)FabaceaeMain
Saccharum officinarum (sugarcane)PoaceaeMain
Solanum tuberosum (potato)SolanaceaeMain
Zea mays (maize)PoaceaeMain

Biology and Ecology

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B. pilosa is a C3 plant with a life cycle of 150–360 days, depending on onset of germination (Kissmann and Groth, 1993). It normally behaves as an annual weed but at least one form, B. pilosa var. radiata, may behave as a perennial.

B. pilosa is a short-day plant, the critical daylength being 15 hours. The plant response to controlled photoperiod depends on the time of year. The minimum period for inducing flowering is between 10 and 14 short days. Induction could only begin with the third pair of leaves fully expanded. Gibberellic acid, chlormequat and 2,4-D had no effect on plants kept in a long-day regime (Kirszenzaft and Felippe, 1978). It forms a dense ground cover, which prevents regeneration of other species. It grows best in full sun.

One isolated plant can produce over 30,000 seeds, which are generally highly viable. However, according to Marinis (1973), the reproductive capacity in a stand of 3.4 individuals/m² was 1205 disseminules/plant. Many of the seeds germinate readily at maturity (Holm et al., 1979) making possible three or four generations per year in some areas (Mitich, 1994).

B. pilosa has a strong taproot and tolerates low humidity, characteristics that allow it to grow in fairly dry places, although it does not do well in sandy soils. It grows mainly where the annual rainfall is >1500 mm (Galinato et al., 1999).

Seeds germinate on the soil surface or in shallow soil (to a depth of 1 cm). Germination depends on light, humidity and oxygen concentration. Seeds at greater depths remain viable in the soil for many years. There is usually a great flush of germination after tillage of the soil during the spring. In meridional Brazil, the weed may be seen all year around but the major period of growth is during spring and summer (Kissmann and Groth, 1993​).

Light and good aeration favour germination but seed can also germinate in the dark. Under continuous fluorescent light, germination was 80–90%. Germination is also induced by brief exposures (2 minutes or longer) to blue, green, red and far-red light. The promotive effect of irradiation with red light is not reversed by far-red light (Valio et al., 1972).

Chivinge (1996) reported that seedlings emerged from the soil surface to a depth of 4 cm, but there was no germination from greater depths. B. pilosa seeds germinated at 20, 25 and 30°C, with the greatest germination (70%) occurring at 25°C. Fertilizer application (Compound D) increased the height and branching of the plants, and the number of heads and seeds per plant, but had no effect on the number of seeds per head, which averaged 44.3. Soaking seeds in water induced germination in less than 24 hours, and germination increased with longer periods of soaking. The longest seedlings (45 mm) and highest germination (65%) came from seeds soaked for 7 days.

Cardoso (1997) reported that the germination rate of B. pilosa was increased by adding either ammonium nitrate or ammonium sulphate to the soil. The dry weight response to nitrogen of B. pilosa seedlings was related to the soil type.

B. pilosa seeds can remain viable for years when buried below the soil surface. Those stored for 3 to 5 years still gave 80% germination (Holm et al., 1977). Sahoo and Jha (1997) studied changes in viability and dormancy of freshly harvested seeds of B. pilosa buried at soil depths of 2, 7 and 15 cm over 1 year. The number of viable and dormant seeds decreased more rapidly in samples from the 2-cm soil depth than in those from greater depths. At 2-cm soil depth, the viable seed population of B. pilosa was reduced by 66%. The enforced and induced dormant seed population increased with increasing soil depth, while the non-dormant (germinable) seed populations showed an opposite trend.

In Natal, South Africa, B. pilosa is one of the first plants to emerge after the spring rains (Shanley and Lewis, 1969). Annual flushes of emergence in Brazil are mainly concentrated in October (85% of total) after the soil is rotary cultivated (Blanco and Blanco, 1991). The optimum temperature range for germination of B. pilosa was 25/20-35/30°C (day/night, 12/12 h). Germination rate decreased above or below this range and temperatures below 15/10°C and above 45/40°C were unfavourable for germination. Seeds can germinate under both a 12-hour photoperiod and a 24-hour dark regime. Maximum emergence occurred when seeds were sown less than 1 cm deep. No seedlings emerged when sown at a depth of more than 10 cm. Flooding, even for a day, following sowing decreased emergence to 25% compared to 56% with no flooding. Seedling emergence decreased sharply with a further increase in the duration of flooding; no seedlings emerged when flooding continued for up to 28 days after sowing (Desbiez et al., 1991).

Germination is affected by moisture availability and decreases with decreasing osmotic potential (Galinato et al., 1999).

Rios et al. (1989) studied the effect of achene size and temperature on the germination percentage of B. pilosa. Germination percentage declined with increasing age of achenes. Alternating temperatures at germination promoted percentage and the speed of germination of small achenes.

The two different kinds of achenes of B. pilosa were tested for germinability and seedling development. Long achenes were found to germinate readily under a wide range of conditions while short achenes showed fairly exacting requirements. Germination of short achenes was enhanced by red light, scarification, hormone leaching and increasing oxygen tension. Seedlings originating from short achenes showed lower survival rates and initial slower development than those originating from long achenes (Forsyth and Brown, 1982).

Rocha (1996) examined the effects of achene heteromorphism within the infructescence on the dispersal capacity of B. pilosa. The central achenes were longer (94.4 vs. 71.8 mm) and heavier (2.10 vs. 1.73 g) than peripheral achenes. In addition, seeds germinated at a higher rate from freshly collected central achenes than from peripheral achenes (88 vs. 52%); however, after 6 months of storage there was no significant difference in the germination of seeds from achenes of the two positions (54 vs. 64%). Moreover, after 9 and 14 months of storage, the germination of seeds from central achenes was lower than that of peripheral achenes (30 vs. 58% and 4.6 vs. 14%, respectively). The viability of freshly collected seeds was independent of the position of the achene within the infructescence (88 vs. 83% for central and peripheral achenes, respectively). Many infructescences (69%) were found to bear achenes only in the peripheral positions, while very few (1.4%) bore achenes only in the central position, indicating that central achenes dispersed earlier than peripheral achenes. Finally, central achenes were more likely to be removed from the infructescence when tested with an artificial dispersal agent, as 40.4% of the infructescences tested had achenes removed from the central positions. In contrast, only 6.4% of the infructescences tested with an artificial disperser had achenes removed from the peripheral positions. These results demonstrate that central achenes are more likely to attach to potential dispersers then peripheral ones.

Amaral and Takaki (1998) reported that achene sizes decreased over the life span of the plant from 5-12 mm at 120 days to 3-10 mm after 237 days. Analysis of the germination percentage confirmed the presence of two distinct classes, formerly defined as short and long achenes. Since length cannot be used for the separation of achenes, the morphological characteristics of the tegument, especially of the ornament, was used for separation of the achenes. Achenes with verrucose tegument (formerly named as short achenes) showed dormancy and light sensitivity and achenes without ornament of the tegument (formerly named as long achenes) showed no dormancy and no light sensitivity for the germination process.

B. pilosa was less dormant after storage and long, thin B. pilosa achenes were less dormant than short, thick ones. Exogenous GA3 had no effect on germination but wounding the distal region of B. pilosa increased germination (Zelaya et al., 1997).

In a citrus grove in Florida, USA, Chandran et al. (1999) observed that B. pilosa numbers were higher in plots receiving thiazopyr alone or thiazopyr with oxyfluorfen than in nontreated plots. At 120 days after treatment (DAT), approximately 90% more B. pilosa plants had emerged in plots receiving thiazopyr than in nontreated plots. A tank mix of thiazopyr plus oxyfluorfen resulted in a 55% increase in B. pilosa number at 120 DAT, thiazopyr antagonized the preemergence activity of oxyfluorfen. Greenhouse studies using seeds collected from sites with or without herbicide history produced similar results.

Fenner (1980) has proved that the leaf canopies of different vegetation types are markedly effective in inhibiting germination of B. pilosa in the field. Similar results were also observed for fresh and old seeds. It was also found that only 1-hour exposure to leaf transmitted light was required to induce almost a complete light requirement in B. pilosa.

Pattison et al. (1998) studied the growth, biomass allocation and photosynthetic characteristics of seedlings of five invasive non-indigenous species, including B. pilosa, and four native species, including B. sandwicensis, grown under different light regimes to help explain the success of invasive species in Hawaiian rain forests. The invasive species had higher growth rates than the native species as a consequence of higher photosynthetic capacities under sun and partial shade, lower dark respiration under all light treatments, and higher leaf area ratios when growing under shade. Overall, invasive species appear to be better suited than native species to capturing and utilizing light resources, particularly in high-light environments such as those characterized by relatively high levels of disturbance.

B. pilosa var. radiata, an aggressive perennial weed of sugarcane in the Ryukyu Islands, Japan, was studied under laboratory conditions. Leaf area, number of shoots and number of flowering heads increased considerably with increasing nitrogen. Main stem length, leaf area and shoot:root ratio increased markedly with increasing amounts of shading. Increasing degree of moisture increased the shoot:root ratio and coefficient of dry matter of above-ground parts but decreased the number of shoots, achene weight/seed head and 1000 grain weight (Ishimine et al., 1987).

The response of B. pilosa to various substrate moisture levels was assessed. Under moderate water stress, energy was devoted preferentially to the reproductive process but under severe stress it was directed to vegetative growth with a substantial increase in the ratio of root to aerial parts. Selective variability, according to changes in substrate moisture, was observed in the size and weight of propagules and in the proportion of achenes with three or more pappi, increasing the chances of dispersal (Capote et al., 1986).

Abd El Ghani (1998) studied the vegetation of the date palm (Phoenix dactylifera) orchards of the Feiran Oasis, south Sinai, Egypt, to describe the weed flora and relate it to some environmental variables. Three main vegetation types were recognized: Zygophyllum simplex-Hordeum murinum, inhabiting the old orchards that occupy the relatively dry lowlands of the Oasis; B. pilosa-Conyza bonariensis in young, highly disturbed (new) orchards; and Polypogon monspeliensis-Malva parviflora in mature orchards. The least diversified vegetation is in young orchards with a high soil moisture and organic matter content.

Zobolo and van Staden (1999) studied the effects of deflowering and defruiting on the growth and senescence of B. pilosa, which is used in traditional medicine to treat malaria, in a field trial at Kwadlangezwa, South Africa. Deflowered plants were generally taller, had a greater shoot weight and higher chlorophyll concentration than those that were only defruited. Fruit and flower heads were responsible for the reduction in leaf and stem growth after flowering. Deflowering is essential if the leaves are to be harvested commercially because it retards senescence and maintains growth.

Becker et al. (1998) reported that a phytosociological group characterized by Anagallis arvensis/B. pilosa was indicative of alkaline, calcareous sites at lower altitudes. It is an indicator of heavy, moist soil (Galinato et al., 1999).

Piccolo and Marinis (1980) studied water loss in B. pilosa seedlings and suggested that very efficient mechanisms existed in the seedlings to stabilize water balance.

Favero et al. (2000) reported C, Ca and N levels in a few volunteer species, including B. pilosa, that were close to or greater than that of legume green manure plants. However, most had K and Mg levels, and several of them, P levels greater than that of the legumes. A major increase in dry matter, and N, P, K and Mg content, begins 49 days after germination (Pitelli et al., 1976).

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Apion luteirostre Parasite Fruits/pods
Asphondylia bidens Parasite Seeds
Cercospora bidentis Pathogen Leaves
Chalcophana viridipennis Herbivore Leaves
Chlamisus insularis Herbivore Leaves
Cropia minthe Herbivore Leaves
Dioxyna chilensis Herbivore Seeds
Ensina hyallipennis Herbivore Seeds
Entyloma guaraniticum Pathogen
Hypercompe hambletoni Herbivore Leaves
Liriomyza Herbivore Leaves
Liriomyza archboldi Herbivore Leaves
Liriomyza insignis Herbivore Seeds
Perrhybris phaloe Herbivore Leaves
Phaedon pertinax Herbivore Leaves
Physimerus pygmaeus Herbivore Leaves
Rhodobaenus cariniventris Herbivore Inflorescence/Stems
Rhodobaenus tredecimpunctatus Herbivore Stems
Sphaceloma bidentis Pathogen
Uromyces bidenticola Pathogen Leaves
Xanthaciura insecta Herbivore Inflorescence

Notes on Natural Enemies

Top of page Sonchus yellow net virus (SYNV) was isolated from Sonchus oleraceus and B. pilosa in Florida, USA. The virus was transmitted mechanically and by the aphid Aphis coreopsidis (Christie et al., 1974). Bidens mosaic virus (BiMV) was first isolated from B. pilosa in Brazil by Kitajima et al. (1961).

Tomato spotted wilt virus (TSWV) causes serious diseases of many economically important plants including ornamentals, vegetables and field crops (Zitter and Daughtrey, 1989). Yellow spot, caused by a strain of the TSWV, is a disease that occurs in most pineapple-growing areas of the world. Weeds, including B. pilosa, are commonly found in and around pineapple (Ananas comosus) fields and are important hosts of the virus (Py et al., 1984).

Bidens mottle virus (BiMoV) was first isolated from B. pilosa and Lepidium virginicum in Florida, USA, by Christie et al. (1968). It infects most varieties of lettuce and endive (Purcifull and Zitter, 1971).

Weeds such as B. pilosa in lemon orchards serve as alternative host plants on which large mite populations can develop (Fourie, 1989).

Meloidogyne hapla has been isolated from B. pilosa roots (Nirmal Singh Gill et al., 1979) while the reproduction index for M. javanica was 42% in B. pilosa (Asmus and Andrade, 1997). Rotylenchulus reniformis populations were strongly correlated with B. pilosa populations in avocado groves in Florida, USA (McSorley and Campbell, 1980).

A wide range of fungi have been detected in B. pilosa seeds. Prete et al. (1984) found the following fungi in the seed of B. pilosa: Cladosporium sp., Alternaria spp., Penicillium sp., Aspergillus sp., Phoma sp., Drechslera spp., Rhizopus sp., Fusarium sp., Epicoccum sp., Curvularia sp., Botryodiplodia sp., Trichoderma sp., Nigrospora sp., Stemphylium sp., Botrytis sp. and Chaetomium sp. Sphaceloma bidentis was found on B. pilosa in many areas in the Kanto region, Japan (Negishi, 1986). B. pilosa and Tagetes minuta were susceptible to infection by Sclerotinia sclerotiorum (Phillips, 1992).

Orobanche ramosa, a phanerogamous parasite, has been found in various crop and weed plants, including B. pilosa (Torres, 1986). Ralstonia solanacearum causes wilt and death in some weeds such as B. pilosa (Kishun and Chand, 1987). Love vine (Cassytha filiformis) also parasitises B. pilosa (Holm et al., 1977).

A coffee-foliage feeding noctuid moth can spread by using B. pilosa as a host (Bardner and Mathenge, 1974). Adults of a wasp-like moth, Empyreuma pugione, have been seen feeding on the flowers of B. pilosa (Adams and Goss, 1978). B. pilosa acts as a host plant of Calcomyza cruciata, a leaf miner in Argentina (Valladares, 1992). Two insects, Protensina hyallipennis and Dioxyna chilensis, have been observed attacking Sonchus oleraceus, S. asper and B. pilosa in Chile (Prado and Nitsche, 1989).

See Waterhouse and Norris (1987) and Waterhouse (1994) for a comprehensive list of natural enemies of B. pilosa. The list here only includes those natural enemies that are host-specific or attack other weeds in addition to B. pilosa.

Means of Movement and Dispersal

Top of page The phenomenal spread and colonization of Bidens species is due partly to their effective pollination mechanisms and their distinctive dispersal adaptations, which allow seed distribution by humans, animals, wind and water (Holm et al., 1997). In the Philippines, it has been reported as a rice crop seed contaminant (Elliot et al., 1993).

Impact

Top of page Soyabean yield loss due to increased density (plants/m²) of B. pilosa was determined in Argentina (Arce et al., 1995). A density of one plant resulted in a yield loss of 9.4%; two plants, 17.3%; and four to eight plants, 28%. Higher densities than eight plants produced a 43% yield loss. Competition primarily affected the number of pods per plant.

Trials on coral limestone at Senbaru, Okinawa, Japan, showed that B. pilosa var. radiata was a serious competitor in sugarcane in terms of leaf area index, leaf dry weight and number of tillers, causing decreases in the main yield-controlling elements. Competition became severe 60 days after crop emergence and caused nearly 80% growth suppression on plots left with no control for 120 days. In contrast, suppression of the weed by the crop was only 10% at 60 days after planting, decreasing by a further 4% up to 120 days (Ishimine et al., 1986).

B. pilosa densities of 183-222 plants/m² reduced the growth of beans (Phaseolus vulgaris) in trials during 1978-79. Shading caused by the weed was the factor most affecting the dry weight of above-ground bean plants (Carvalho, 1980). B. pilosa at a density of 1.85 plants/m² produced a reduction of 18.75% of total bean production. Ten plants/m² caused a reduction of 48.9% (Cerna and Valdez, 1987). Blanco et al. (1996) reported that B. pilosa reduced the biomass, number and weight of bean plants and seeds. There was a significant, negative correlation between weed density and bean growth.

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Panicum fauriei (Carter's panicgrass)NatureServe NatureServe; USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition (unspecified)US Fish and Wildlife Service, 2011
Scaevola coriacea (dwarf naupaka)NatureServe NatureServe; USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition (unspecified)US Fish and Wildlife Service, 2010a
Schiedea spergulina var. leiopodaNational list(s) National list(s); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2010b

Risk and Impact Factors

Top of page Impact mechanisms
  • Competition - monopolizing resources
  • Competition

Uses

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It is the herbaceous flowering plant, having white 'petals' around a intense bunch of orange florets, and it has been reported to possess effective pharmacological properties like Antibacterial activity, Anti-inflammatory and antiallergic activity, Antimalarial Activity, T helper cell modulator, Immunosuppressive antihyperglycemic, anti-hypertensive, antiulcerogenic, hepatoprotective, anti-leukemic, anticancer, antipyretic, anti-virus, anti-angiogenic, anti-rheumatic, antibiotic. Biden spilosa has various chemical constituents like polyacetylenes, Polyacetylenic glycosides, aurons, auron glycosides, p-coumeric acid derivatives, caffeoylquinic acid derivatives, pheophytins, diterpenes, tannins, phytosterols, ascorbic acid, carotene, essential oils, saponins, steroids and flavonoids and many others were recognized in this plant (Bairwa et al., 2010). 

Phenylheptatriyne, an insecticidal allelochemical extracted from B. pilosa, was tested for its effects on mixtures with dillapide (extracted from Piper cubeba) on 10-day old larvae of Ostrinia nubilalis. Dillapide did not enhance the toxicity of the other allelochemicals, but when applied alone, it was toxic to larvae and inhibited their growth (Bernard et al., 1990). Phenylheptatriyne strongly inhibited germination of macroconidia and growth of mycelia of the cereal pathogen Fusarium culmorum in the presence of near-UV radiation. Photosensibilization of macroconidia was fungicidal and was not reversed after repeated washings in PHT media (Bourque et al., 1984).

A methylated chalcone glucoside was isolated from the leaves of B. pilosa and its structure was elucidated by spectroscopic methods (Hoffman and Holzl, 1988). Leaves of this weed are used in Africa to treat inflammation and rheumatism. Hoffman and Holzl (1988) reported the isolation of two new chalcones: acylated okanin 4-O-glucoside and okanine 3-O-beta-D-glucoside.

From the methanolic extract of whole plants of B. pilosa the new beta-D-glucopyranosyloxy-3-hydroxy-6(E)-tetradecen-8,10,12-triyne and a known polyine (phenylhepta-1,3,5-triyne) were isolated and identified mainly by IR and NMR methods. Phenylhepta-1,3,5-triyne exhibited activity against Pseudomonas aeruginosa, Trichophyton mentagrophytes, Microsporum gypseum and Spodoptera frugiperda. The new compound exhibited activity against T. mentagrophytes and promoted the proliferation of normal and carcinogenic human cell lines in culture (Alvarez et al., 1996).

Aerial parts of B. pilosa from Uganda were extracted with CH2Cl2. Reversed-phase preparative HPLC of the extract resulted in the isolation of 5-O-methylhoslundin, caffeine and vanillic acid. This is thought to be the first report of 5-O-methylhoslundin from the Asteraceae family (Sarker et al., 2000). Zulueta et al. (1995) isolated a new diterpene-phytiyl heptanoate from B. pilosa.

In the Philippines, B. pilosa is used to treat rheumatism, sore eyes, abdominal troubles, ulcers, swollen glands and toothache. In Mexico, it is used to treat stomach disorders, haemorrhoids and diabetes and it also possesses antimicrobial properties (Alvarez et al., 1996).

In Polynesia, the leaves and flowers are brewed into a tea, used as a tonic and 'blood purifier' and for treating throat and stomach ailments. In Rapa and the Marquesas, it is used as a poultice. In Mexico, the leaves are also used for brewing a medicinal tea. In Tonga, an infusion of the leaves is used to treat cuts and boils and is dripped on to eye ailments thought to have a supernatural origin. In the Cook Islands, a wad of chewed or pounded leaves is commonly applied to cuts (Whistler, 1992).

The Igorots of Bontoc (Philippines) mix B. pilosa with grains of rice to make rice wine (Galinato et al., 1999).

B. pilosa has a long history of use by the indigenous people of the Amazon and virtually all parts of the plant are used. In the Peruvian Amazon, it is used for aftosa, angina, diabetes, dysentery, dysmenorrhea, edema, hepatitis, jaundice, laryngitis and worms. In Piura, a decoction of the roots is used for alcoholic hepatitis and worms. The Cuna tribe mixes the crushed leaves with water to treat headaches. Near Pucallpa Peru, the leaf is balled up and applied to a toothache and the leaves are also used for headaches. In other parts of the Amazon a decoction of the plant is mixed with lemon juice and used for angina, sore throat, water retention, hepatitis and dropsy. The Exuma tribes grind the sun-dried leaves with olive oil to make poultices for sores and lacerations.

Taylor (1998) provides detailed documentation of medicinal properties and ethnic uses of rainforest plants, including B. pilosa.

It is used as an indigenous leafy vegetable (ILF) in southern Africa.

Uses List

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Human food and beverage

  • Beverage base

Materials

  • Pesticide

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

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B. pilosa is easily recognized by the elongated bur-like fruits that bear recurved or hooked bristles that have played an important role in its spread (Holm et al., 1977). B. pilosa in the strict sense is distinguished from the very closely related B. odorata and B. alba by its fertile ray florets, and by usually having at least three awns on the achenes. Grossman and Groth (1993) distinguish a further species, B. subalternans, on the basis that it has four awns on the achene, but other authors treat this as synonymous with B. pilosa. Several other Bidens species can occur as weeds but are readily distinguished by their more divided leaves (e.g. B. bipinnata) and/or deep yellow flowers (e.g. B. biternata).

Prevention and Control

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Cultural Control

B. pilosa can be controlled by persistent mowing, hoeing and hand pulling in order to prevent seed production. Thorough cultivation discourages growth (Pope, 1968).

Mechanical weeding in row crops, such as soyabeans and maize, may help to partially control B. pilosa. The effect of various soil management techniques on seedling emergence was as follows (in decreasing order of effect): disc harrow + roller, rotavator, disc harrow and contact herbicide (Blanco and Arévalo, 1991).

A maize-bean intercropping system effectively suppressed weeds, including Melanthera aspera and B. pilosa, when the crops were sown at high densities in Nicaragua (Salomon, 1990).

Soil Solarization

Transparent and black polyethylene sheets were evaluated for soil solarization in a field study conducted in Bangalore, India, during 1996. After 15 and 30 days of soil solarization, the polyethylene sheets were removed from tobacco seedling nurseries. The predominant weeds were Cyperus rotundus, Cynodon dactylon, Commelina benghalensis, Euphorbia hirta, Leucas aspera, Tridax procumbens and B. pilosa. The number and dry weight of weeds were substantially less with transparent than with black polyethylene and the unweeded control at 21 and 42 days after sowing. Transparent polyethylene solarization increased tobacco seedling dry matter production and the 30- and 15-day treatments gave better benefit:cost ratios then black polyethylene, mulching, hand weeding and pendimethalin treatments.

A field trial was conducted in Costa Rica to evaluate the effects of different periods (weeks) of solarization, namely: 0, 2 (103 cumulative hours of sunshine), 4 (188) and 7 (288), in combination with chicken manure additions (4.1 t/ha) on propagule survival of B. pilosa. The greatest propagule death occurred after 7 weeks of solarization, and the addition of chicken manure further decreased the propagules. This treatment also sharply decreased the soil weed seed bank; shorter periods were not as effective (Herrera and Ramirez, 1996).

Biological Control

The natural enemies of B. pilosa have not been investigated in detail as potential biological control agents. Those that have not been recorded as having other hosts which are useful plants are listed in the table of natural enemies. Waterhouse (1994) considers the agromyzid flies as the most promising. The fungal pathogens in the list of natural enemies are all likely to be host specific and so they are also potential biological control agents.

Chemical Control

Chemical control of B. pilosa is dependent on the crop species. The main crop groups and herbicides are summarized below.

Coffee: sulfosate, glyphosate, paraquat + diuron and paraquat (Echegoyen et al., 1996)

Roses, papaya and cabbage: oxyfluorfen, although some failures have been reported with this herbicide

Roses: atrazine, glyphosate and simazine

Citrus and plum orchards: glyphosate

Groundnuts: 2,4-D

Onions: lactofen (somewhat phytotoxic) and linuron give adequate control

Maize: atrazine and nicosulfuron (Ferreira et al., 1996)

Wheat: pendimethalin

Soyabeans: the following herbicides/mixtures may be used: glyphosate + 2,4-D amine or ester, paraquat + 2,4-D amine, cyanazine, metribuzin, fomesafen, bentazone, linuron + metribuzin + diclofopmetil, glyphosate + linuron + metholachlor, lactofen, imazethapyr + chlorimuron-ethyl, lactofen + imazethapyr, fomesafen + chlorimuron, propaquizafop/oxasulfuron + lactofen, haloxyfop-methyl/chlorimuron + lactofen, metolachlor, metolachlor + imazaquin, sulfentrazone, diclosulam, propaquizafop followed by oxasulfuron + lactofen and haloxyfop-methyl followed by chlorimuron-ethyl + lactofen (Laca Buendia et al., 1999).

Cotton: diuron, diuron + pendimethalin and diuron + trifluralin (Vieira et al., 1998b)

Pineapple: diuron

Potato: metribuzin

Rice: 2,4-D, MCPA and fenoxaprop + metsulfuron (Melhoranca, 1999).

Sesame: diuron + pendimethalin (Vieira et al., 1998a)

Sugarcane: fluometuron and ametryn.

Grapes: diuron, dichlobenil and simazine (Paulo et al., 1997)


Herbicide resistance

In trials in Kenya in 1987-90, paraquat failed to control B. pilosa growing in arabica coffee interrows (Njoroge, 1991). These biotypes are resistant to paraquat and they may be cross-resistant to other bipyridilium herbicides. Gabard et al. (1998) reported that azafenidin controlled paraquat-susceptible and paraquat-resistant B. pilosa.

Resistance of B. pilosa to imazaquin has been reported in Brazil (Heap, 1997). The intensive and repetitive use of acetolactate synthase (ALS) herbicides in São Gabriel do Oeste county, MS, Brazil, and in the provinces of Córdoba and Tucumã, Argentina, selected resistant biotypes of B. pilosa. Resistance was first observed after six applications of imazaquin/chlorimuron to soyabean. Christoffoleti and Foloni (1999) reported that a biotype of B. pilosa was resistant to all tested ALS herbicides and had a high degree of cross resistance to sulfonylurea and imidazolinone herbicides. Particular biotypes are resistant to chlorimuron-ethyl, imazaquin, imazethapyr, nicosulfuron and pyrithiobac-Na and they may be cross-resistant to other ALS herbicides. Lactofen, fomesafen and bentazone controlled both resistant and susceptible populations.

Other chemicals

Valarini et al. (1996) completely inhibited the germination of B. pilosa seeds with a 10% aqueous suspension of lemon grass (Cymbopogon citratus) oil. However, this concentration was phytotoxic with respect to the emergence of bean. Igarashi et al. (1997) reported that resormycin isolated from the cultured broth of a streptomycete strain isolated from a soil collected at Yokohama-shi, Kanagawa Prefecture, Japan, and identified as S. platensis MJ953-SF5, markedly inhibited the growth of monocotyledonous and dicotyledonous weeds, including B. pilosa.

References

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Arce OE, Robinet HA, Mansilla de Andrada N, Dfaz y BE, Guillén S, 1995. Determinación de pérdidas de cultivo de soja (Glycine max) por competencia de saetilla (Bidens subalternans) en el noroeste de la provincia de Tucumán-Argentina. Res·menes XII Congreso Latinoamericano de Malezas, Montevideo, Uruguay.

Asmus GL, Andrade PJM, 1997. Reproduction of Meloidogyne javanica in some weed species frequently found in the western region of Brazil. Comunicado Te^acute~cnico - EMBRAPA Centro de Pesquisa Agropecua^acute~ria do Oeste, No. 19:3 pp.; 10 ref.

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Christoffoleti PJ, Foloni LL, 1999. Dose response curves of resistant and susceptible Bidens pilosa to ALS inhibitor herbicides. 1999 Brighton crop protection conference: weeds. Proceedings of an international conference, Brighton, UK, 15-18 November 1999., Volume 1:159-162; 4 ref.

Desbiez MO, Tort M, Thellier M, 1991. Control of a symmetry-breaking process in the course of the morphogenesis of plantlets of Bidens pilosa L. Planta, 184(3):397-402

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Favero C, Jucksch I, Costa LM, Alvarenga RC, Neves JCL, 2000. Growth and nutrient accumulation by volunteer plants and by legumes used for green manure. Revista Brasileira de Cie^circumflex~ncia do Solo, 24(1):171-177; 19 ref.

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