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Rhamphicarpa fistulosa

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Rhamphicarpa fistulosa

Pictures

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PictureTitleCaptionCopyright
Rhamphicarpa fistulosa; flower during daytime, when the corolla it is still closed. May, 2010.
TitleHabit
CaptionRhamphicarpa fistulosa; flower during daytime, when the corolla it is still closed. May, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; flower during daytime, when the corolla it is still closed. May, 2010.
HabitRhamphicarpa fistulosa; flower during daytime, when the corolla it is still closed. May, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; in vegetative stage. May, 2010.
TitleHabit
CaptionRhamphicarpa fistulosa; in vegetative stage. May, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; in vegetative stage. May, 2010.
HabitRhamphicarpa fistulosa; in vegetative stage. May, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; flowers and capsules of maturing plants - showing reddish coloration as a sign of maturity. May, 2010.
TitleFlowers and capsules
CaptionRhamphicarpa fistulosa; flowers and capsules of maturing plants - showing reddish coloration as a sign of maturity. May, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; flowers and capsules of maturing plants - showing reddish coloration as a sign of maturity. May, 2010.
Flowers and capsulesRhamphicarpa fistulosa; flowers and capsules of maturing plants - showing reddish coloration as a sign of maturity. May, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; close view of capsule on maturing plants, showing reddish coloration as a sign of maturity. May, 2010.
TitleCapsule
CaptionRhamphicarpa fistulosa; close view of capsule on maturing plants, showing reddish coloration as a sign of maturity. May, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; close view of capsule on maturing plants, showing reddish coloration as a sign of maturity. May, 2010.
CapsuleRhamphicarpa fistulosa; close view of capsule on maturing plants, showing reddish coloration as a sign of maturity. May, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; invasive habit, in seed production stages, in a rain-fed, lowland rice field. Benin. September, 2010.
TitleInvasive habit
CaptionRhamphicarpa fistulosa; invasive habit, in seed production stages, in a rain-fed, lowland rice field. Benin. September, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; invasive habit, in seed production stages, in a rain-fed, lowland rice field. Benin. September, 2010.
Invasive habitRhamphicarpa fistulosa; invasive habit, in seed production stages, in a rain-fed, lowland rice field. Benin. September, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; invasive habit. Infested, rain-fed, lowland rice field. Benin. September, 2010.
TitleInvasive habit
CaptionRhamphicarpa fistulosa; invasive habit. Infested, rain-fed, lowland rice field. Benin. September, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; invasive habit. Infested, rain-fed, lowland rice field. Benin. September, 2010.
Invasive habitRhamphicarpa fistulosa; invasive habit. Infested, rain-fed, lowland rice field. Benin. September, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; natural enemy. the Nymphalid herbivorous caterpillar Junonia spp., natural enemy of  R. fistulosa, on another parasitic weed, Striga asiatica (witch weed). June, 2010.
TitleNatural enemy
CaptionRhamphicarpa fistulosa; natural enemy. the Nymphalid herbivorous caterpillar Junonia spp., natural enemy of R. fistulosa, on another parasitic weed, Striga asiatica (witch weed). June, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; natural enemy. the Nymphalid herbivorous caterpillar Junonia spp., natural enemy of  R. fistulosa, on another parasitic weed, Striga asiatica (witch weed). June, 2010.
Natural enemyRhamphicarpa fistulosa; natural enemy. the Nymphalid herbivorous caterpillar Junonia spp., natural enemy of R. fistulosa, on another parasitic weed, Striga asiatica (witch weed). June, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; a boy putting freshly picked R. fistulosa plants on the fire, using the smoke as an insect repellent. Glazoué, Benin. September, 2010.
TitleUsing smoke as an insect repellent
CaptionRhamphicarpa fistulosa; a boy putting freshly picked R. fistulosa plants on the fire, using the smoke as an insect repellent. Glazoué, Benin. September, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; a boy putting freshly picked R. fistulosa plants on the fire, using the smoke as an insect repellent. Glazoué, Benin. September, 2010.
Using smoke as an insect repellentRhamphicarpa fistulosa; a boy putting freshly picked R. fistulosa plants on the fire, using the smoke as an insect repellent. Glazoué, Benin. September, 2010.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Baatè/Sokponta, Glazoué, Benin. September, 2008.
TitleInvasive outcome
CaptionRhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Baatè/Sokponta, Glazoué, Benin. September, 2008.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Baatè/Sokponta, Glazoué, Benin. September, 2008.
Invasive outcomeRhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Baatè/Sokponta, Glazoué, Benin. September, 2008.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop.  Casamance (between Nianga and Tanaf), Senegal. October, 2008.
TitleInvasive outcome
CaptionRhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Casamance (between Nianga and Tanaf), Senegal. October, 2008.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop.  Casamance (between Nianga and Tanaf), Senegal. October, 2008.
Invasive outcomeRhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Casamance (between Nianga and Tanaf), Senegal. October, 2008.©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Kyela, Tanzania. May, 2010.
TitleInvasive outcome
CaptionRhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Kyela, Tanzania. May, 2010.
Copyright©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Kyela, Tanzania. May, 2010.
Invasive outcomeRhamphicarpa fistulosa; rice farmer showing R. fistulosa that has invaded her crop. Kyela, Tanzania. May, 2010. ©Jonne Rodenburg/AfricaRice
Rhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Bongolava, Tsiraonomandidy, Madagascar. March, 2013.
TitleInvasive outcome
CaptionRhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Bongolava, Tsiraonomandidy, Madagascar. March, 2013.
Copyright©Mamadou Cissoko/AfricaRice
Rhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Bongolava, Tsiraonomandidy, Madagascar. March, 2013.
Invasive outcomeRhamphicarpa fistulosa; rice farmers showing R. fistulosa that has invaded their crop. Bongolava, Tsiraonomandidy, Madagascar. March, 2013. ©Mamadou Cissoko/AfricaRice

Identity

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Preferred Scientific Name

  • Rhamphicarpa fistulosa (Hochst.) Benth.

Other Scientific Names

  • Macrosiphon elongatus Hochst.
  • Macrosiphon fistulosus (Sysnonym of R. longiflora) Hochst.
  • Rhamphicarpa longiflora (Indian species most related to R. fistulosa) Benth.

Local Common Names

  • Benin: corico; efri; otcha
  • Côte d'Ivoire: loho soukoh; soukoh lo
  • India: tutari (R. longiflora)
  • Madagascar: angamay
  • Tanzania: mbosyo; mulungi; ntengo ya nchele nchele
  • Uganda: kayongo
  • Zambia: mogogatau

Summary of Invasiveness

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R. fistulosa is a broad-leaved, annual, facultative hemi-parasitic forb species very widespread in the wetlands of tropical Africa (Staner, 1938). It has also been reported in India, New Guinea and Australia. No hard evidence is published on the invasiveness of R. fistulosa. Although R. fistulosa is not yet considered to be a widespread problem, it has the potential to become more important in the near future (Raynal Roques, 1994; Rodenburg et al., 2010; 2011a), especially since it can develop into a parasitic weed when it encounters a suitable host plant (e.g. Akoegninou et al., 1999). It parasitizes cereal crops like rice and there are indications that it is increasingly common on rain-fed lowland rice (Rodenburg et al., 2011b). Given its very widespread distribution (more than 35 countries in sub-Saharan Africa), the species is likely to be, or become, a very serious parasitic weed, threatening rice production in the continent.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Scrophulariales
  •                         Family: Orobanchaceae
  •                             Genus: Rhamphicarpa
  •                                 Species: Rhamphicarpa fistulosa

Notes on Taxonomy and Nomenclature

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Rhamphicarpa fistulosa (Hochst.) Benth is an angiosperm species of the Lamiales order, Orobanchaceae family (formerly Scrophulariaceae; Olmstead et al., 2001) and the genus Rhamphicarpa (Bentham, 1835; Hochstetter, 1841; Bentham, 1846; Engler, 1895; Hansen, 1975; Philcox, 1990; Mielcarek, 1996; Fischer, 2004). Its phylogenetic position is not yet completely confirmed but seems to be within the lineage of Radamaea/Sieversandreas genera (Fischer et al., 2012).

The genus name Rhamphicarpa is a combination from the Greek words for ‘beak’ or ‘bill’ and ‘fruit’. The beaked fruit is a characteristic feature of the genus (Hansen, 1975) and can be used to distinguish between the genera Cycnium and Rhamphicarpa (Staner, 1938). Bentham (1835) was the first to describe a species of this genus, Rhamphicarpa longiflora. Independently from this work, Hochstetter (1841) named the genus Macrosiphon and described two African species, M. fistulosus and M. elongatus. These are currently considered synonyms of Rhamphicarpa longiflora and R. fistulosa, respectively (Hansen, 1975). Since Bentham’s first description, many additional species have been described within the genus RhamphicarpaHooker (1884) and van Steenis (1970), considered the African, the Australian and the Indian species to be different. The Australian plants were named R. australiensis Steen., but as van Steenis did not compare this species to the African or Caucasian species, this name was not widely acknowledged. Hansen (1975) observed that the distinction between plant types is mainly based on different shapes of the fruit or calyx, but these inherently show some degree of variation that does not necessarily imply existence of different species. Hansen (1975) therefore concluded that Rhamphicarpa fistulosa (Hochst.) Benth. is the correct name of the species occurring in New Guinea, Australia, Madagascar and Africa, while R. longiflora Wight ex. Benth. is the Indian species of this genus. This is still the currently accepted taxonomic division (Philcox, 1990; Mielcarek, 1996).

Description

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R. fistulosa is a broad-leaved, annual, facultative hemi-parasitic forb species found in wetlands in tropical Africa (e.g. Hansen, 1975; Ouédraogo et al., 1999). When these wetlands are used for crop production, the species may develop into a (parasitic) weed (Bouriquet, 1933; Rodenburg et al., 2011b).

Plants are erect and slender, smooth, simple-stemmed to much-branched and glabrous, and can reach up to 120 cm high (depending on locality) (Philcox, 1990).

Leaves

The species has reduced filiform, or pinnatisect (needle-like), bright green leaves, 10-60 mm long, with filiform segments (Hansen, 1975). The leaves and stem can turn reddish upon physiological maturity (J Rodenburg, personal observation). Mature plants are very branched.

Roots

R. fistulosa has a fibrous root system with branched, but weak, white roots that are often connected to grass (Poaceae) host plant roots, if growing in their vicinity. R. fistulosa parasitizes the host by its roots, through a special organ called ‘haustorium’, also used by other parasitic plants such as Striga spp. and Orobanche spp. (Parker and Riches, 1993; Press and Graves, 1995). Whereas Striga species develop both terminal and lateral haustoria, R. fistulosa, like other facultative parasites such as Buchnera hispida, develops only lateral haustoria (e.g. Neumann et al., 1997). The haustorium connects the parasite and host root xylem (Kuijt, 1969; Neumann et al., 1998a). Upon establishment of a xylem-to-xylem connection the parasite can extract host metabolites, nutrients and water from its host. The biomass accumulated by a parasitizing R. fistulosa plant is usually much smaller than the biomass lost by the affected host plant (Rodenburg et al., 2011b), but it is not clear whether this is caused by any additional pathological or phytotoxic mechanisms (Rodenburg et al., 2010).

Flowers

Flowers are solitary in axils of, or just above, bracts. Pedicels 9-20 mm long. Bracteoles 1-5 mm long, inserted near midway on pedicel. Calyx 3.5-9 mm long; tube 0.5-2 mm long, 1-4 mm in diameter; lobes ovate at base with revolute margins, 2-5 mm long, filiform. Corolla white, cream, pale pink or pale blue (white form most common in Africa), externally stipitate-glandular; tube 25-30 mm long, 1 mm broad below, 1.5-2 mm broad above, straight or slightly curved; lobes 6-9 x 5-8 mm, circular to spathilate, rounded; corolla long persisting around the maturing capsule. Stamens inserted. Anthers 2-3.5 mm long. Ovary 3-4 x 1.5-2 mm. Style 17-30 mm long slightly exerted (Hansen, 1975). Capsule 7-10 mm long to apex of beak, 4-7 mm broad, winged along sutures.

Fruits

Fruits are asymmetrical, neatly beaked capsules about the size of a small pea - 6-15 mm long and 4-7 mm broad (Hansen, 1975). Fruits contain 100-250 small dark brown seeds (e.g. Ouedraogo, 1995; Ouédraogo et al., 1999; Gbèhounou and Assigbé, 2003). The beaked fruit is a characteristic feature of the genus Rhamphicarpa (Hansen, 1975).

Seeds

Seeds are small (0.2 × 0.55 mm) and oval-shaped (broader at the chalazal). The outer seed coat forms a reticulate network covered by prominent ridges and devoid of any protuberances (e.g. Mielcarek, 1996; Ouédraogo et al., 1999). Seeds weigh about 0.011 mg (Rodenburg et al., 2011).

Plant Type

Top of page Annual
Broadleaved
Herbaceous
Parasitic
Seed propagated

Distribution

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R. fistulosa is a very widespread wetlands species in tropical Africa (Staner, 1938). It has been reported in West and Central Africa (Müller, 2007) and in East and Southern Africa (e.g. Rodenburg et al., 2010; 2011b). Outside Africa it is reported in India, New Guinea and Australia (Hansen, 1975; USDA, 2013). In Australia, it is mainly found in the (tropical) northern part of Queensland (Martin, 2000).

Species of the genus Rhamphicarpa occur in the tropics of Africa and Asia, South Africa, Madagascar, the Caucasus and the Asian part of Turkey. It is not clear yet how the genus could have spread to such discontinuous and remote places. Continental drift is unlikely to be the cause as the size of the genus Rhamphicarpa is small and the morphological variation is limited, implying that the species have a young phylogenetic age. Rhamphicarpa is assumed to be monophyletic, with a common ancestry and a common place of origin. It is hypothesized that the genus Rhamphicarpa originated in Africa and that R. fistulosa represents the ancestral stock, as this species is the most widely distributed and the only taxon that is found in more than one sub-area (Hansen, 1975). From Africa the genus may have spread to other areas, while subsequent environmental changes (e.g. in climate) may have caused a break-up of the original distribution area in the currently observed discontinuous sub-areas (Hansen, 1975).

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

Africa

AngolaPresentHansen, 1975; Mielcarek, 1996
BeninLocalisedRodenburg et al., 2011b; Akoegninou et al., 1999; Gbehounou and Assigbe, 2003; HCNF, 2013
BotswanaPresentHansen, 1975; Philcox, 1990; Mielcarek, 1996; USDA-ARS, 2013
Burkina FasoPresentPress et al., 1987; Ouedraogo, 1995; Neumann et al., 1999; Ouédraogo et al., 1999
BurundiPresentHansen, 1975; Mielcarek, 1996
CameroonPresentHansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
Central African RepublicPresentHansen, 1975; USDA-ARS, 2013
ChadPresentHansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
CongoPresentHansen, 1975
Congo Democratic RepublicWidespreadStaner, 1938; Hansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
Côte d'IvoireLocalisedS. N'cho personal communication; HCNF, 2013; Konan et al., 2013North: Boundiali (villages: Gueguerin, Kpafono), Ferke region, Korhogo (village: Zontakaha)
EgyptPresentMielcarek, 1996
EthiopiaPresentHansen, 1975; Mielcarek, 1996; EAH, 2013; USDA-ARS, 2013
GabonPresentHansen, 1975
GambiaPresentHansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
GhanaPresentHansen, 1975; Mielcarek, 1996; Johnson et al., 1998; USDA-ARS, 2013
GuineaPresentHansen, 1975; Cisse et al., 1996; USDA-ARS, 2013
Guinea-BissauPresentHansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
KenyaPresentHansen, 1975; EAH, 2013; USDA-ARS, 2013
MadagascarPresentM.Cissoko, personal communication; Bouriquet, 1933; Staner, 1938; Hansen, 1975; Mielcarek, 1996; Fischer et al., 2012; USDA-ARS, 2013'localised and invasive in Bongolava, Tsironmandidy'
MalawiPresentHansen, 1975; Philcox, 1990; Mielcarek, 1996; USDA-ARS, 2013
MaliPresentHansen, 1975; Ouedraogo, 1995; Mielcarek, 1996; Ouédraogo et al., 1999; USDA-ARS, 2013
MozambiquePresentHansen, 1975; Philcox, 1990; Mielcarek, 1996; USDA-ARS, 2013
NamibiaPresentUSDA-ARS, 2013
NigerPresentMielcarek, 1996; HCNF, 2013; USDA-ARS, 2013
NigeriaPresentHansen, 1975; Mielcarek, 1996; Gworgwor et al., 2001; USDA-ARS, 2013
SenegalPresentJ.Rodenburg, personal observation; Hansen, 1975; Mielcarek, 1996; Johnson et al., 1998; Ouédraogo et al., 1999; USDA-ARS, 2013'South-west (Casamance) between Nianga and Tanaf (abouth 100 km South-west of Kolda)
Sierra LeonePresentHansen, 1975
South AfricaPresentStaner, 1938; Hansen, 1975; Mielcarek, 1996; USDA-ARS, 2013
SudanPresentHansen, 1975; Mielcarek, 1996; Kayeke et al., 2010; EAH, 2013; USDA-ARS, 2013; USDM, 2013
TanzaniaPresentPresent based on regional distribution.
-ZanzibarLocalisedEAH, 2013Pemba Island (Mayonjwa)
TogoPresentHCNF, 2013; Houngbédji and Gibot-Leclerc, 2015
UgandaPresentJ. Rodenburgh, personal observation, 2013; Hansen, 1975; Mielcarek, 1996; EAH, 2013; USDA-ARS, 2013'widespread in Namutumba District: Nsinze Sub-country, Bukonte Parish, Busalifu Village and Ivukula sub-county, Ivukula Parish, Ivukula Village'
ZambiaPresentHansen, 1975; Philcox, 1990; Mielcarek, 1996; EAH, 2013; USDA-ARS, 2013
ZimbabwePresentHansen, 1975; Philcox, 1990; Mielcarek, 1996; USDA-ARS, 2013

Oceania

AustraliaPresentMielcarek, 1996
-Australian Northern TerritoryPresentHansen, 1975Tropical northern parts
-QueenslandPresentMartin, 2000Davies Creek, Mareeba
-Western AustraliaPresentUSDA-ARS, 2013
Papua New GuineaPresentHansen, 1975; Mielcarek, 1996; USDA-ARS, 2013

History of Introduction and Spread

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When its natural habitats (wetlands) are turned to production (mainly of rice), and when a suitable host is grown as a high density monoculture, a naturally occurring R. fistulosa population can rapidly build up and become an agricultural pest (e.g. Gbèhounou and Assigbé, 2003; Rodenburg et al., 2011b).

 R. fistulosa is a relatively unknown species at present and therefore it is often unnoticed by local extension and research (as observed in Benin, Cote d’Ivoire, Madagascar, Senegal, Tanzania and Uganda). The extent of the problem of Rhamphicarpa in rain-fed lowland rice in sub-Saharan Africa is therefore expected to be hugely underestimated. Recent observations in West Africa indicate the species is spreading, at least to a certain extent. Rodenburg et al. (2011b) observed an increase in the number of infested inland-valleys grown to rice over a period of about ten years; in 1998, R. fistulosa was found in three out of nine inspected valleys, while in 2007, five out of nine of them were infested. In Cote d’Ivoire, farmers indicated an observed general increase of the species in the period 2008-2012 (Konan et al., 2013). In Senegal, R. fistulosa was observed in a rice field in the Casamance, south of the Gambia, in 2008 (J Rodenburg, personal observation), where it had previously - during an annual survey in the period between 1985 and 1996 - not been observed (Ouédraogo et al., 1999). In Madagascar (Bongolava, Tsiraonomandidy), farmers indicated an increase in R. fistulosa in their rice fields over the past years (M Cissoko and AP Andrianaivo, personal communication).

Risk of Introduction

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R. fistulosa seeds are minute and can stick to crop seeds harvested from infested fields; if these crop seeds are then marketed, R. fistulosa can be introduced to previously uninfested fields when the newly obtained seeds are sown. In this way human dispersal is a likely cause of R. fistulosa introductions, and its seeds could travel long distances along with rice or other crop seeds (Hansen, 1975).

Rice is an increasingly important crop in sub-Saharan Africa. To keep pace with increasing rice consumption, about 30 million tons more rice per year will be needed by 2035 (Seck et al., 2012). Much of the increase in production is likely to come from area expansion. Low-lying areas, such as the inland valleys, with a relatively favourable hydrology and soil fertility, constitute high-potential areas for rice production and are likely to be increasingly exploited for that purpose (e.g. Rodenburg et al., 2013c). Such intensification of rice production in these ecosystems may in some areas be threatened by infestations of R. fistulosa (Johnson et al., 1998). Given its very widespread distribution (more than 35 countries in sub-Saharan Africa), the species is likely to be, or become, a very serious parasitic weed, threatening rice production in the continent.

Other likely means of introduction include flood water and free-roaming cattle, whereby seeds are transported on the fur or hooves of the animals, or are ingested by animals at one place and deposited in their droppings in another place.

Habitat

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R. fistulosa thrives in wet and semi-aquatic environments in forest and savannah zones (e.g. Cissé et al., 1996). It can grow in peaty soils over rock substratum, and on or between rocks on shallow, slow running streams, but more frequently in grassy swamps, temporary or permanently flooded areas like inland valley swamps, and poorly drained rain-fed lowland rice fields (Hansen, 1975; Ouédraogo et al., 1999; Rodenburg et al., 2010; 2011b).

Within rain-fed lowland rice production systems it is found in the hydromorphic zones near the valley bottom (Rodenburg and Johnson, 2009).

R. fistulosa can be found from sea level to 2,150 m above sea level (Hansen, 1975).

Ouédraogo et al. (1999) reported R. fistulosa in brackish water near the sea, which would imply a high degree of salinity tolerance. The exact range of salinity it can tolerate needs to be confirmed.

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
 
Terrestrial – ManagedCultivated / agricultural land Present, no further details Harmful (pest or invasive)
Terrestrial ‑ Natural / Semi-naturalNatural grasslands Present, no further details
Riverbanks Present, no further details
Wetlands Principal habitat
Littoral
Coastal areas Present, no further details
Freshwater
Rivers / streams Present, no further details
Ponds Present, no further details

Hosts/Species Affected

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R. fistulosa parasitizes wild grass species (of the Poaceae family) and is a facultative hemi-parasitic weed on cereal crops like rice, maize and millet (Bouriquet, 1933; Kuijt, 1969; Cissé et al., 1996; Ouédraogo et al., 1999). Groundnut Arachis hypogaea L. (Bouriquet, 1933) and cowpea Vigna unguiculata (L.) Walp. (Kuijt, 1969) have been reported as hosts too, although the latter report concerned R. veronicaefolio Vatke (= Cycnium veronicifolium Vatke), rather than R. fistulosa (Fuggles-Couchman, 1935).

Rice, particularly direct seeded rice (Johnson et al., 1998), is the most affected crop, as this is the only major cereal crop that can be grown in the temporary flooded conditions of the rain-fed lowlands where R. fistulosa thrives (Rodenburg et al., 2010; 2011b).

Supposedly R. fistulosa can also parasitize members of the monocot Cyperaceae as well as the eudicot Leguminosae and Labiatae families (Bouriquet, 1933). It is very unusual for a parasitic plant species to be able to parasitize both monocotyledons and eudicotyledons, and so these reports need to be confirmed.

R. fistulosa is a facultative hemi-parasite and as such it is not dependent on the presence of a host to complete its life cycle. However, the parasite obtains a reproduction advantage from parasitizing a suitable host plant (Ouédraogo et al., 1999; Rodenburg et al., 2011b).

Host Plants and Other Plants Affected

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Growth Stages

Top of page Flowering stage, Fruiting stage, Vegetative growing stage

Biology and Ecology

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Reproductive Biology

Flowers are white and fragrant and only open at dusk; flowers usually last only one night, after which they fall off (Cissé et al., 1996). They appear one by one as the plant grows, and in the same sequence they are replaced by seed capsules. Independently growing plants develop fewer flowers (often just one or very few) than plants that have established a successful parasitic relationship with a suitable host (Ouédraogo et al., 1999).

Its reproductive biology is unclear. Some reports mention cross-pollination by night moths (Parker and Riches, 1993; Cissé et al., 1996; Ouédraogo et al., 1999), perhaps because of the shape of the corolla, which is compatible with hawk-moth pollinations (e.g. Fischer et al., 2012), and the fact that the flowers only open between sunset en sunrise, but viable seeds have been produced, in controlled screen house environments, in the absence of such insects (J Rodenburg, personal observation). The species may produce well over 1,000 small seeds per plant.

Physiology and Phenology

R. fistulosa uses the C3 pathway for CO2 assimilation (Press et al., 1987). Contrary to some reports classifying R. fistulosa as an obligate hemi-parasite (e.g. Parker and Riches, 1993), the species can survive without a host (Ouédraogo et al., 1999; Rodenburg et al., 2011b), as it is able to provide part of its own carbon through CO2 assimilation (Press et al., 1987). However, R. fistulosa is pale green (both stem and leaves), which indicates a low chlorophyll content (Hansen, 1975), presumably related to the hemi-parasitic nature of the plant species. Plants that are able to parasitize on a suitable host are able to accumulate more biomass and have a higher reproductive rate compared to plants that grow independently (Ouédraogo et al., 1999; Rodenburg et al., 2011b).

The rhizodermis of R. fistulosa roots consist of a one-cell layer. All along the radicle rhizodermis are about 800 µm-long root hairs. The root cortex is composed of an endodermis and a hypodermis, with parenchymatous aerenchyma in between (Ouédraogo et al., 1999). The species is adapted to semi-aquatic environments, with large air spaces between the cortical cells of the root aerenchyma to facilitate air-flow in submerged conditions, and with a partly reduced indumentum (coverage by fine hairs) on aerial parts (partly reduced compared to those of other parasitic species of the Orobanchaceae family) (Neumann et al., 1997; Ouédraogo et al., 1999). R. fistulosa roots can develop haustoria, resembling those of other facultative hemi-parasites like Buchnera hispida Buch. Han. Ex. D. Don (Nwoke and Okonkwo, 1974; Neumann et al., 1998b; 2001). Phenolic substances and/or lignins can be observed where the parasite attempts to penetrate the host root, indicating the existence of a host-plant defence reaction (Neumann et al., 1999).

Seeds have a 6-month dormancy period after which they require water and daylight for germination (Ouédraogo et al., 1999). Seed dormancy is broken by a pre-conditioning period of 2-3 weeks under humid and warm conditions (Gbehounou and Assigbé, 2004). In contrast with obligate parasitic plants (e.g. Striga spp.), the seeds of the hemi-parasitic R. fistulosa do not need a host-derived stimulant for germination (Ouédraogo et al., 1999; Gbehounou and Assigbé, 2004). Germination occurs within about 4 days when the conditions are met. 2-3 days after germination the green cotyledons emerge, after which the seedling starts to develop leaves.

About 3-4 weeks after sowing of the host plant, upon contact between the parasite and the host root, the parasite starts to develop haustoria (Neumann et al., 1998a). Haustorium initiation starts with the development of tiny hairs around the area of outgrowth on the root, which sometimes facilitate the attachment of the parasite with the host root (Neumann et al., 1998a). If the host root and the parasite root are parallel to each other, the parasite root can develop multiple haustoria. Without a host in its vicinity, the parasite does not develop haustoria, indicating that some morphogenic host-root factors are involved in the host-detection of the parasite (Neumann et al., 1998a). Flowering and maturity times seem to vary with growing conditions. Ouédraogo et al. (1999) reported initiation of flowering around 140 days after sowing (DAS) in trials in Burkina Faso, but an earlier onset of flowering (around 70-100 DAS) has been observed at other locations (J Rodenburg, personal observation). R. fistulosa plants can continue and finalize growth and reproduction beyond the harvest of the crop, provided that there is enough residual soil moisture.

Longevity

Little is known about seed longevity under natural conditions, but according to Gbèhounou and Assigbé (2004) seeds are short-lived (approximately 1 year). Seeds of R. fistulosa have a dormancy period of six months after which then can readily germinate when conditions are favourable (Ouédraogo et al., 1999).

Associations

R. fistulosa is often associated with other semi-aquatic plants (Hansen, 1975; Deil, 2005; Müller and Deil, 2005). In a recent study carried out in Kyela, southern Tanzania, species found to be consistently and solely associated with R. fistulosa were Oryza longistaminata A. Chev. and Roehr., Ammannia auriculata Willd., Fimbristylis littoralis Gaudich., Mariscus longibracteatus Chermezon and Scleria vogelli C. B. Clarke (Kabiri et al., 2013).

Observed associated wild plant or weed species are: Parahyparrhenia annua (Hack.) W. D. Clayton, Sacciolepis microcorra Mez., Panicum spp. or wild rice (Oryza spp.) in Senegal, Burkina Faso and Mali. Whether or not any of these plants are also parasitized by R. fistulosa has not been confirmed.

R. fistulosa has some geographic overlap with other parasitic weeds such as Alectra vogelii Benth. in Guinea (Cissé et al., 1996) Striga aspera (Willd.) Benth. in Guinea (Cissé et al., 1996) and Burkina Faso (Sallé et al., 1994); Striga asiatica (L.) Kuntze in Tanzania (Johnson et al., 1998; Kayeke et al., 2010; Kabiri et al., 2013) and Madagascar (M Cissoko and AP Andrianaivo, personal communication), and S. hermonthica Benth. in Mali, Burkina Faso (Sallé et al., 1994) and Uganda (J. Rodenburg, personal observation).

Environmental Requirements

R. fistulosa has a fairly distinct environmental niche, as it is primarily found on seasonally flooded soils (Hansen, 1975; Deil, 2005; Müller and Deil, 2005) and shows little ecological plasticity. Philcox (1990) described its preferred habitats as ranging from shallow, slow-running streams to river banks and grassy swamps. In areas where rice is grown all along the upland-lowland continuum, R. fistulosa is only found in the lower, seasonally flooded zones (Kabiri et al., 2013).

R. fistulosa prefers saturated soil (Kabiri et al., 2013) and, contrary to earlier reported observations of the species in irrigated rice (Bouriquet, 1933), it is currently understood that the species should not be submerged at the germination and seedling stages (van 't Klooster, 2011); the likelihood of finding R. fistulosa in rice systems using permanent and controlled flooding is therefore low. Indeed, in R. fistulosa-infested rice fields, the parasite is usually observed in patches where the soil is saturated but only barely, or where it is only temporarily flooded (Parker and Riches, 1993; J. Rodenburg, personal observation). Soils favouring R. fistulosa are generally poor in N, P and K, with a relatively high silt content (e.g. Ouédraogo et al., 1999; Kabiri et al., 2013), although peaty soils over rock substratum have also been frequently reported (Philcox, 1990).

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])

Soil Tolerances

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Soil drainage

  • impeded
  • seasonally waterlogged

Soil reaction

  • acid
  • neutral

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • infertile
  • shallow

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Athelia rolfsii Pathogen Whole plant not specific
Bacillus megaterium Pathogen Whole plant not specific
Bacillus pumilus Pathogen Whole plant not specific
Fusarium Pathogen Whole plant not specific
Junonia Herbivore Whole plant not specific
Smicronyx Herbivore not specific

Notes on Natural Enemies

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Fungi species like Fusarium spp. and Sclerotium rolfsii, and bacteria like Stenotrophomonas maltophilia, Bacillus pumilus and B. megaterium have been observed to be pathogenic to R. fistulosa (Sikirou et al., 2002a). The species can also be attacked by beetles and caterpillars. The Nymphalid caterpillar Junonia spp. has frequently been observed on R. fistulosa plants and is able to feed on all the above-ground plant tissue (J Rodenburg, personal observation). The Coleoptera (beetle) Smicronyx spp., of the family of Curculionideae, has also been observed to cause foliar damage to R. fistulosa plants, and to lay eggs in the seed capsules (Sikirou et al., 2002a). The larvae of these beetles feed on the immature seeds in the capsule and make the capsule look swollen (J Rodenburg, personal observation).

Means of Movement and Dispersal

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Natural Dispersal

Wind and water can disperse R. fistulosa seeds, although the geographic range of dispersal is not known. Seeds are dust-like, tiny (0.2 × 0.55 mm) and light (0.011 mg), and can therefore easily be carried by wind and travel medium to long distances. Water should be considered an even more important natural means of dispersal. R. fistulosa grows in natural wetland vegetation or rain-fed lowland agricultural fields. Under these conditions, uncontrolled temporary flooding occurs frequently and seed can be transported by flood water into water ways and enter other areas. No published studies are available on the importance of these means of dispersal of R. fistulosa seeds.

Vector Transmission (Biotic)

The most likely means of dispersal via animals is by the intake of seed-bearing plants by free-roaming cattle in infested fields – something often observed in the agricultural systems where R. fistulosa constitutes a weed problem (J, Rodenburg, personal observation). After ingestion, cattle can excrete still-viable seeds in their droppings in other, uncontaminated fields. Seeds can also be carried on the fur or hooves of these animals. Such means of dispersal is believed to be over relatively short distances, i.e. the typical distances these cattle cover. No published studies are available on the importance of such or other means of dispersal of R. fistulosa seeds.

Accidental Introduction

The parasitic plant can also be accidentally introduced when farm implements used in contaminated field are not cleaned before their use in uncontaminated fields. Seed dispersal through crop seeds is another likely scenario. The small seeds of R. fistulosa can stick to crop seeds that are harvested in infested fields and sown in uninfested fields, or exchanged between farmers through informal seed systems lacking quality control measures (such as local markets and farmer-to-farmer seed exchange).

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Animal productionSeeds can be transported on the fur or hooves of animals or be dispersed through ingestion and dropp Yes
Crop productionPresumably dispersed through informal (farmer-to-farmer) seed exchange Yes
Digestion and excretionPresumably dispersed by free-grazing cattle Yes
Flooding and other natural disastersPresumably seeds are dispersed through flood water as species occurs in temporary flooded areas (wet Yes
Interconnected waterwaysUncontrolled flooding of contaminated fields can cause seed dispersal into streams and rivers Yes
Seed tradeSeeds of invader can stick to (much) larger crop seeds. In theory this could disperse seeds over lon Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Host and vector organismsCattle Yes
LivestockFree-grazing cattle can transport seeds on fur and hooves and through ingestion and excretion Yes
Machinery and equipmentPoorly-cleaned equipment used in contaminated fields could cause new infestations in new fields Yes
WaterUncontrolled floods can transport seeds into waterways that could transport seeds over long distance Yes
WindSeeds are tiny and could be transported by wind Yes

Impact Summary

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CategoryImpact
Economic/livelihood Negative

Economic Impact

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In R. fistulosa-infested rice fields, yield losses of 30-100% are recorded in Benin (Sikirou et al., 2002a; Gbèhounou and Assigbé, 2003; Rodenburg et al., 2011b) and in Tanzania (Kayeke et al., 2010). Exact economic impacts of R. fistulosa are unknown and even reasonably reliable estimations are difficult to provide, mainly because the regional incidences of the species in rain-fed rice areas is as yet unclear. What is known is that the species occurs, in natural vegetation or in rice fields, in at least 35 countries in tropical and sub-tropical Africa, at least 26 of which have rain-fed lowland rice production systems. Based on 2007 estimates presented by Rodenburg and Demont (2009), these 26 countries produce about 3.1 M tonnes of paddy from rain-fed rice systems, worth around US $1.5 billion per year. In a country like Benin, an estimated 22% of the inland valleys where rice is grown are infested by R. fistulosa (Rodenburg et al., 2011b). Assumed this is representative for the larger region, and using 30% of R. fistulosa-inflicted yield losses as a conservative estimate for R. fistulosa-infested rice fields, the current annual economic losses in sub-Saharan Africa could be around US $99 million. This estimate needs to be revised once more reliable data become available in the near future.

Environmental Impact

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In natural vegetation R. fistulosa may parasitize wild grasses. Wild grasses that are parasitized could show reduced seed production and may therefore be less successful, resulting in a lower share of the particular species in the local plant community. No published work is available to confirm this however.

Social Impact

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The social impact of R. fistulosa is not easily measured and no published certain information is available on this. Poorer people are the most likely to be impacted socially. The parasitic weed is primarily problematic on marginal arable land, i.e. on low-fertility and poorly-drained soils where water cannot be controlled. These are the typical crop production conditions of resource-poor subsistence farmers, many of which are women (e.g. Rodenburg et al., 2013c). The weed has clear negative economic impacts and requires the farmer to invest valuable time for weeding (e.g. Konan et al., 2013). Weeding is often done by women and children; time that could otherwise be invested in family welfare and education (e.g. Rodenburg and Johnson, 2009). Sometimes heavily infested fields are abandoned by the farmer (e.g. Rodenburg et al., 2011b).

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Has a broad native range
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Benefits from human association (i.e. it is a human commensal)
  • Has high reproductive potential
Impact outcomes
  • Host damage
  • Negatively impacts agriculture
  • Negatively impacts livelihoods
Impact mechanisms
  • Competition
  • Parasitism (incl. parasitoid)
Likelihood of entry/control
  • Difficult to identify/detect as a commodity contaminant
  • Difficult/costly to control

Uses

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Little is known about the economic, social or environmental value of R. fistulosa. The species has been observed locally (in central Benin) being used as insect repellent; fresh plants were burned in a portable stove to produce smoke that was believed to repel biting insects like mosquitos (J Rodenburg, personal observation). The plant was also reported to have medicinal uses in Machipi (near Ifakara), Kilombero District, Tanzania (EAH, 2013).

Uses List

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Materials

  • Pesticide

Medicinal, pharmaceutical

  • Traditional/folklore

Detection and Inspection

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R. fistulosa is a relatively unknown species at present and therefore it is often unnoticed by local extension and research (as observed in Benin, Cote d’Ivoire, Madagascar, Senegal, Tanzania and Uganda). The species is also easily overlooked as the flowers are only opening at sunset (Cissé et al., 1996).

R. fistulosa can be confused with several species, including Cycnium recurvum (Oliv.) Engl. (previously named R. fistulosa recurva Oliv. and R. tenuisecta Standl.), which has a similar plant type and overlapping distribution in parts of North-East and South-East Africa. However, the tube of the corolla of C. recurvum is about one third of that of R. fistulosa. Moreover, C. recurvum has a distinctly different habitat, favouring dry conditions (Mielcarek, 1996).

The closely-related genera Rhamphicarpa and Cycnium are distinguished by the form of the capsules and the presence of a beak on their capsules: Rhamphicarpa have oblique ovoid capsules with beaks, whereas Cycnium have straight oblong capsules without a beak (Cycnium) (Staner, 1938).

Another distinctive feature is the stamens: Rhamphicarpa stamens are didynamous, arising at 2 levels in the corolla tube, and the style exceeds the stamens, whereas in Cycnium the style never exceeds the lower pair of stamens, and stamens are equal in length, arising at 1 level in the corolla tube (Philcox, 1990; Fischer, 1999; Leistner, 2005).

Due to their parasitic nature, and similarities in host crop ranges, local names given by farmers are often the same for both R. fistulosa and Striga spp. (J Rodenburg, personal observation). R. fistulosa is sometimes even referred to as ‘the Striga of rice’, even though both R. fistulosa and Striga spp. parasitize rice. Striga spp. are usually found on rice grown in the free-draining uplands, whereas R. fistulosa parasitizes rice in the water-logged lowlands and hydromorphic zones.

Similarities to Other Species/Conditions

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In literature prior to Staner’s (1938) revision, many species that are now considered to be part of the genus Cycnium were classified as R. fistulosa; for example, the hemi-parasitic Cycnium veronicifolium (Vatke) Engl. used to be called R. fistulosa veronicaefolio Vatke (Fuggles-Couchman, 1935) or R. elliotii S. Moore (The Plant List, 2010). A recent molecular phylogenetic study, the first of this type conducted on Rhamphicarpa, seems to point at a much closer lineage with the genera Radamaea and Sieversandreas than with Cycnium (Fischer et al., 2012). It would involve more such molecular phylogenetic analyses to ascertain this. There is still however no conclusive evidence that Cycnium and Rhamphicarpa are really separate genera.

R. fistulosa is very similar to five other species in the genus Rhamphicarpa: R. longiflora, R. elongata, R. brevipedicellata,R. capillacea and R. medwedewii. R. medwedewii is only found in the Caucasus. The species R. fistulosa is most often confused with R. longiflora, but they also differ in distribution, as R. longiflora is only found in India. The taxa can further be distinguished by the form of the beak of their capsules; R. fistulosa has a straight beak, whereas R. longiflora has an oblique beak (Bentham, 1846).

In central Africa R. fistulosa can be easily confused with R. capillacea, which also has long white flowers and favours similar growth conditions (Raynal, 1970). R. capillacea can be distinguished from the other Rhamphicarpa species by its leaves (entire for R. capillacea compared to pinnatisect for the others) and capsules (isodiametric for R. capillacea compared to variable and never isodiametric for the others) (Raynal, 1970; Hansen, 1975).

R. longiflora and R. elongata have narrowly triangular calyx lobes, whereas R. brevipedicellata and R. fistulosa have calyx lobes with a broad base and a subulate to filiform tip. The latter two species can then be distinguished by the pedicels, which are short in R. brevipedicellata (1-6 mm) and long in R. fistulosa (5-30 mm) (Hansen, 1975).

Finally, R. fistulosa can be confused with Striga species that have the same host range (mainly S. hermonthica, S. asiatica or S. aspera). The morphological differences between the species are clear - i.e. the long straight corolla tube and predominantly white flowers of R. fistulosa compared to the much shorter corolla tube and predominantly pink or red/orange flowers of Striga spp. (e.g. Parker and Riches, 1993)

Due to their parasitic nature, and similarities in host crop ranges, local names given by farmers are often the same for both R. fistulosa and Striga species (J Rodenburg, personal observation). R. fistulosa is sometimes even referred to as ‘the Striga of rice’, even though both R. fistulosa and Striga species parasitize rice - the Striga species are usually found on rice grown in the free-draining uplands whereas R. fistulosa parasitizes on rice in the water-logged lowlands and hydromorphic zones.

Prevention and Control

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Prevention

As with other parasitic weeds of the Orobanchaceae family, the spread of R. fistulosa via their tiny seeds can be prevented with basic phytosanitary measures. This means that any possible vector, bringing seeds from an infested area to an uninfested place, should as much as possible be cancelled out (e.g. Goldwasser and Rodenburg, 2013). Farm implements should be cleaned of soil remnants before being used again in another field. Cattle movement between contaminated and clean fields should be avoided. Fields should be bunded to prevent seeds entering with water following uncontrolled floods. Crop seeds should be cleaned before sowing.

Control

R. fistulosa can be controlled with the post-emergence herbicide 2,4-D (Gbèhounou and Assigbé, 2003). Fertilizer has a proven suppressive effect on R. fistulosa and a positive effect on rice yields in R. fistulosa-infested fields (Sikirou et al., 2002b; Rodenburg et al., 2011b; Kayeke et al., 2013). Resource-poor rice farmers could use rice husks, that are often freely available, as it has been proven to reduce the negative effects of R. fistulosa infestation on yield (Kayeke et al., 2013).

Genetic variation in resistance and tolerance levels has been observed among rice cultivars (Rodenburg et al., 2011).

It is also hypothesized that improved water management and controlled flooding can reduce R. fistulosa abundance (e.g. Parker and Riches, 1993; van 't Klooster, 2011; Parker, 2012; Goldwasser and Rodenburg, 2013). Permanently flooded conditions, starting at the early stages of the crop, will contribute to reduced R. fistulosa plant numbers (van 't Klooster, 2011).

Transplanting is also likely to have a positive effect on rice performance in R. fistulosa-infested fields (Gbèhounou and Assigbé, 2003; Goldwasser and Rodenburg, 2013), as it will give the crop a time advantage over the weed, thereby making it more competitive (e.g. Rodenburg and Johnson, 2009). It has the additional advantage of allowing for hand weeding, the spot-application of post-emergence herbicides or the use of a rotary weeder (e.g. Rodenburg and Johnson, 2009; Rodenburg et al., 2013b).

Timing of planting has also been observed to be important. R. fistulosa numbers and capsule production were significantly lower in an early-sown rice crop than in a later-sown crop (Langeloo, 2013; Rodenburg et al., 2013a). However, whether or not early or late sowing is advantageous most probably depends on the local environmental conditions, in particular the hydrology and rainfall distribution. Exact relationships between environmental conditions, timing and parasitism should therefore be further investigated. An integrated management strategy against R. fistulosa, combining any of the above measures, is however generally considered the most effective and sustainable solution (e.g. Sallé et al., 2000; Kayeke et al., 2010; Goldwasser and Rodenburg, 2013).

Gaps in Knowledge/Research Needs

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R. fistulosa was described in 1835 by Bentham, and its taxonomy, biology, ecology and agronomic importance has been studied infrequently ever since (e.g. Hansen, 1975; Neumann et al., 1998a; Ouédraogo et al., 1999; Rodenburg et al., 2011b). Despite these efforts, the species remains relatively unknown and many gaps in knowledge still need to be filled. Such insights are required for the development of control strategies to prevent that the species from becoming a more important constraint to food production, particularly in sub-Saharan Africa. Ten important research topics identified are listed below (in no particular order):

  1. Invasiveness of the species R. fistulosa need to be studied. Is the distribution still increasing, stable or decreasing?
  2. The main distribution mechanisms and the history of the spread of the genus over the discontinuous areas need to be clarified.
  3. Its environmental plasticity with relation to altitude and  temperature need to be confirmed. The soil chemical and mechanical (structure) ranges of the R. fistulosa habitat need to be established. The salinity and acidity tolerances are important parameters to help infer on the likely spread of the species.
  4. The current economic loss estimate of US $99 million per year should be revised using updated figures on R. fistulosa incidences and yield losses in rain-fed rice systems per country, as well as rice prices.
  5. Whether or not Cycnium and R. fistulosa are distinct genera is still awaiting affirmative evidence. It is likely that future molecular analyses will provide such evidence.
  6. It is yet not conclusively proven that species of the closely related genus Cycnium and all of the species of the genus R. fistulosa are hemi-parasitic and whether there are also obligate as well as facultative parasites amidst them.
  7. The host range of R. fistulosa (and other parasitic plants of the Rhamphicarpaand Cycnium genera) need to be confirmed as it will determine whether crop rotations, inter- or relay cropping are useful control methods and, if so, which species should be used and which not. In some old publications, some of the Rhamphicarpa (or Cycnium) species have been reported to be able to parasitize both monocotyledons and dicotyledons (Bouriquet, 1933; Fuggles-Couchman, 1935). While this is highly unlikely, it seems still in need of being confirmed.
  8. The host-parasite and damage mechanisms need to be elucidated; whether this can purely be defined as a sink-source relation or whether R. fistulosa negatively affects the host-plant hormone balance, and, through that, the host metabolism and growth.
  9. Host resistance and tolerance mechanisms, and the genes responsible, need to be identified and transferred to adapted (rice) cultivars.
  10. Control strategies for (rice) farmers need to be further investigated and developed. In particular, the timing of crop and weeding operations and soil fertility management seem to be promising avenues to explore further.

References

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Bentham G, 1835. Synopsis of the Buchnereae, a tribe of Scrophulariaceae. Companion to the Botanical Magazine, 1:356-384.

Bentham G, 1846. Ordo CXLII. Scrophulariaceae. Prodomus systematis naturalis regni vegetabilis [ed. by Candolle, A. De]. Paris, France 186-586.

Bouriquet G, 1933. A Scrophulariacee pest of rice in Madagascar. (Une Scrophulariacee parasite du riz a Madagascar.) Revue de Pathologie Vegetale et d'Entomologie (Journal of Vegetable Pathology and Entomology Agricole), 20:149-151.

Cisse J; Camara M; Berner DK; Musselman LJ, 1996. Advances in parasitic plant research: 6th Parasitic Weeds Symposium. Cordoba, Spain [ed. by Moreno, M. \Cubero, J. \Berner, D. \Joel, D. \Musselman, L. \Parker, C.]. 518-520.

Deil U, 2005. A review on habitats, plant traits and vegetation of ephemeral wetlands - a global perspective. Phytocoenologia, 35(2/3):533-705. http://www.ingentaconnect.com/content/schweiz/phyt/2005/00000035/F0020002/art00017

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Gbehounou G; Assigbe P, 2004. A study on germination of seeds of Rhamphicarpa fistulosa (Hochst.) Benth. a new pest of rice. A study on germination of seeds of Rhamphicarpa fistulosa.

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HCNF, 2013. Rhamphicarpa fistulosa (Hochst.) Benth. Herbarium specimen at Herbier du Centre National de Floristique. Abidjan, Cote d'Ivoire: Universite Felix Houphouet-Boigny.

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Links to Websites

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WebsiteURLComment
Africa Rice Centerwww.africarice.org
AFROweedswww.afroweeds.org
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.
International Parasitic Plants Societywww.parasiticplants.org/
PARASITE projectwww.parasite-project.org
South African Association of Botanistswww.sabotany.co.za
The Plant Listhttp://www.theplantlist.org
Weedsbookhttp://www.afroweeds.org/network/

Organizations

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Côte d'Ivoire: Africa Rice Center (AfricaRice), www.africarice.org

UK: Kew Roayl Botanical Gardens (Kew), www.kew.org

USA: Germplasm Resources Information Network (GRIN), www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?31068

Contributors

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02/07/13 Original text by:

Jonne Rodenburg, Africa Rice Center, Tanzania

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