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Research Project Final Report
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SID 5 (Rev. 3/06)
Project identification
Development of eradication strategies for Ludwigia
Centre for Ecology and Hydrology
CEH Wallingford
Maclean Building
Crowmarsh Gifford
Oxon, OX10 8BB
54. Total Defra project costs
(agreed fixed price)
5. Project:
Page 1 of 8
start date ................
22 August 2006
end date .................
31 March 2007
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Executive Summary
The executive summary must not exceed 2 sides in total of A4 and should be understandable to the
intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together
with any other significant events and options for new work.
The objective of this project was to establish the extent of Ludwigia in the UK and determine an
appropriate method for the eradication of the species before it becomes widespread.
Several reports of Ludwigia have been received, but as the species is not perceived as a threat by the
general public, less interest has been shown in the species than would have been desirable.
We have produced a distribution map for the current known locations. This will be updated and possibly
put on a dedicated website for the control of Ludwigia.
We have shown that the herbicide glyphosate achieves approximately 75% reduction in biomass in one
year, which is not sufficient to control or eradicate the species in the long term, even with two treatments.
The addition of 2,4-D amine at 10% of the recommended label rate did not increase the long term
percentage control of the species.
Control of approximately 75% was achieved using glyphosate and glyphosate + 2,4-D amine mixtures.
However control of 97.81% was achieved using the glyphosate and non-oil soya sticking agent (code
name TFWLM1) . We assume that this is due to prolonged slow release of the herbicide into the plant,
increasing the opportunity for continued inhibition of appropriate enzyme system targeted by glyphosate.
We had assumed that the addition of 2,4-D amine to the mixture at sub-lethal levels would encourage the
uptake of glyphosate into the plant. While this technique has been shown to be effective on Japanese
Knotweed (TCM personal communication) it does not appear to have any effect on this species.
The non-oil soya sticking agent is not yet registered for use in Europe, but has shown considerable
potential in trials and field use in the USA. We intend to encourage the company to register the product in
Europe for the start of the 2008 spraying season.
We were able to achieve near eradication of Ludwigia peploides within one growing season, preventing
flowering and seed set using glyphosate and a soya sticking agent.
SID 5 (Rev. 3/06)
Page 2 of 8
Project Report to Defra
As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with
details of the outputs of the research project for internal purposes; to meet the terms of the contract; and
to allow Defra to publish details of the outputs to meet Environmental Information Regulation or
Freedom of Information obligations. This short report to Defra does not preclude contractors from also
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The report to Defra should include:
 the scientific objectives as set out in the contract;
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 a discussion of the results and their reliability;
 the main implications of the findings;
 possible future work; and
 any action resulting from the research (e.g. IP, Knowledge Transfer).
The species in Britain
There are reports of two species of Ludwigia occurring in Britain, Ludwigia peploides and Ludwigia uruguayensis.
The latter is also known as L. grandiflora because of its very large flowers (c 5cm in diameter). It is also
differentiated from L. peploides by possession of hirsute leaves and stems. To date I have not found or been sent
any samples resembling L. uruguayensis and I conclude that the horticultural misnomer has been used for
specimens of L. peploides. This does not exclude the possibility of L. uruguayensis occurring in natural locations
in the UK.
For this reason I have concentrated on the biology, ecology and control of L. peploides in this report.
Scientific Name: Ludwigia peploides (Kunth) Raven
Synonyms: Jussiaea californica (L.) Jeps., Jussiaea patibilcensis Kunth, Jussiaea peploides Kunth, Jussiaea
polygonoides Kunth, Jussiaea repens L. vars. peploides (Kunth) Griseb., Jussiaea californica Wats.
Common Name: floating primrose-willow, creeping water-primrose
Other synonyms: the species of often sold as Jussiaea grandiflora, the synonym of L. uruguayensis,
although I do not believe that this is the correct nomenclature. I believe it is a name adopted by the
horticultural trade because it sounds better – grandiflora implying showy flowers etc..
Description and Variation
Ludwigia peploides is a herbaceous, perennial, wetland obligate plant, which can be categorized as a creeping
macrophyte (Rejmánková, 1992), meaning that is it an emergent macrophyte with stems that grow prostrate to
the mud or float on the water’s surface. Stems are fleshy and reach a length between 20-300 cm long and are
typically glabrous (smooth and hairless) or villosulous (slightly pubescent) with long, soft hairs. Leaves are
alternately arranged are variable in shape and size. They can be lanceolate (longer than wide and usually
tapering at both ends), oblanceolate (broader above the middle of the leaf, then tapering at base), or obovate
(egg-shaped, wider at leaf tip), although leaves are typically round during the early growth period. Petiole length
ranges between 2.5-3.7 cm, and the leaf blade ranges in length between 1-9 cm. The leaf veins are light green
and pinnately arranged.
L. peploides forms two kinds of roots: those for substrate anchorage and nutrient absorption; and adventitious
roots, which occur at the stem internodes and can absorb atmospheric oxygen. They are also important for the
survival of plant fragments. Flowers are long-stalked, occur in the axils, and have five bright yellow petals (1.0-1.5
cm in length) and typically ten stamens surrounding a cylindrical, short-styled ovary containing numerous ovules.
The calyx is bright green, and sepals are between 3-12mm. The fruit capsule is hard, cylindrical, 4-5 chambered,
and often droop on a long (ca. 9 cm) stalk. Seeds (including endocarp) are 1 mm and uniseriate (arranged in
single row) in each locule (chamber).
SID 5 (Rev. 3/06)
Page 3 of 8
Ludwigia peploides is morphologically similar to other noxious water-primrose L. hexapetala and L. uruguayensis.
They can only be differentiated when flowering: L. peploides flowering stems typically grow prostrate and the
petals are usually 1-1.5 cm and the anthers are 1-1.7 mm whereas L. uruguayensis flowering stems grow erect
and its petals are larger, 1.5-2.5 cm, and the anthers are 2.5-3.5 mm. Additionally, the two bractlets (small,
specialized leaves at the base of the flower) of L. peploides are deltate (triangular) or ovate (egg-shaped),
whereas the bractlets of L. hexapetala are ovate to obovate.
There are three subspecies of L. peploides: glabrescens; montevidensis; and peploides. While both subspecies
montevidensis and peploides occur in California, only peploides is native. The subspecies montevidensis is native
to southern South America (Ditomaso and Healy, 2003). These two subspecies can be differentiated by foliage
surface, leaf apex (leaf tip when it attached to stem) and fruit capsule size. According to Ditmaso and Healy
(2003), in peploides, the leaves are glabrous (smooth and hairless), the leaf apex is not glandular, and the fruit
capsules are 10-25 mm. In montevidensis, the leaves are pubescent with glandular hairs, the leaf apex is
glandular, and the fruit capsules are 25-40 mm.
Economic Importance
The floating mats reduce water flow, increase sedimentation, lower pH and dissolved oxygen, and can harbour
disease-carrying mosquitoes. It can easily spread between waterways, and once established, L. peploides is very
difficult to control. The European and Mediterranean Plant Protection Organization added to their EPPO Alert List
in 2004. The New Zealand Plant Conservation Network lists it as an Unwanted Plant Organism.
The dense, sprawling mats, which can weigh 2 kg/m 2 (dry weight) (Cemagref, 2004) clog waterways, can impede
navigability, hunting, fishing, irrigation, and water drainage (EPPO, 2004). The reduction of water flow increases
sedimentation, which further reduces water flow (Cemagref, 2004). The mats also displace native wetland plants
(Grillas, 1992 as cited in Azner et al., 2003), including native Myriophyllum in France, which provides habitat for
many macroinvertebrates upon which some fish feed (Cemagref, 2004). The mats also reduce pH and dissolved
oxygen in the water (Cemagref, 2004), making the habitat less hospitable for many aquatic organisms. By
outcompeting wetland grasses, L. peploides can reduce grazing space for livestock when it displaces wetland
grasses (Cemagref, 2004), since the plant is unpalatable due to concentrations of saponins and calcium oxalate
(EPPO, 2004). As with L. hexapetala, it could easily be dispersed by shipping, waterfowl, and human activity;
moreover, this plant can be spread geographically through the aquarium and horticultural trade (EPPO, 2004).
Once established, canal systems facilitate its spread into connected marshes (Aznar et al., 2003). The fast growth
rate of L. peploides allows it to dominate areas quickly. For example, it only took five years for a small population
of Ludwigia (few dozen square meters) to cover 321 acres (1.30 Km 2) in France (EPPO, 2004). Floating mats of
this plant can indirectly increase mosquito populations by making the larvae inaccessible to mosquito-eating fish
(Pillsbury, 2005).
Ludwigia peploides has potential for wastewater treatment, especially in areas where it is considered native,
because its nitrogen-absorbing capabilities exceed those of water hyacinth, Eichhornia crassipes (Rejamánková,
L. peploides is a perennial aquatic herb that can grow horizontally on water or mud and can emerge over the
water surface. The plant can tolerate water depths up to three meters and grows up to 80 cm above the water
surface (EPPO, 2004). It grows in dense mats along shorelines and out into the water. While it typically inhabits
the margins of lakes, ponds, ditches and streams, L. peploides can also tolerate dry spells (Rejmankova, 1992).
Its negative geomorphic (growing upward instead of towards the ground) roots are capable of absorbing
atmospheric oxygen, allowing the plant to tolerate environmentally stressful condition. Moreover, L. peploides can
grow under a range of nitrogen levels. However, when L. peploides is introduced to favourable, nutrient-rich
conditions, it quickly becomes a dominant competitor (Rejmánková, 1992). It thrives where sites are disturbed
(e.g., dredging and water level fluctuations), because these disturbances stress emergent vegetation that would
otherwise dominate over L. peploides (Rejmánková, 1992).
SID 5 (Rev. 3/06)
Page 4 of 8
Geographic Distribution
L. peploides and L. uruguayensis originate from South America (Argentina and Chile), and they can now be found
in North America, Africa, Australia and Europe. Data on their geographical distribution is lacking and complicated
by the fact that the genus Ludwigia is under revision.
It is non native and invasive in the following countries:
United Kingdom Portugal.
North America
The current distribution of known records is shown in the following Figure. This is up to date as of 26 th October
2007. There are unconfirmed reports of this species in Wales, but we have been unable to substantiate this
SID 5 (Rev. 3/06)
Page 5 of 8
Growth and Development
Biomass doubling time under outdoor experimental conditions in California is 23 days (Rejmánková, 1992) and
has been estimated at 15-20 days under stagnant, natural conditions and 70 days under flowing water conditions
in France (Cemagref, 2004). The mean biomass (dry weight) under controlled conditions averaged 652 g m -2 and
has been recorded at 2 Kg m -2 dry weight in the field in France (Cemagref, 2004). However, field samples
collected from California in Rejmánková’s study (1992) only ranged between 500-700 g m-2 dry weight. Growth
appears to be limited by physical space, as opposed to intraspecific competition resulting from overcrowding
(Rejmánková, 1992). The crop growth rate of L. peploides has been measured at 4 to 50 g m -2 d-1, exceeding that
of the noxious weed waterhyacinth, Eichhornia crassipes (Rejmánková, 1992).
L. peploides spreads primarily through plant fragmentation. Under controlled conditions, a single L. peploides
plant was able to regenerate to 67% of its initial biomass in just 45 days after 95% of the stem was removed
(Rejmánková, 1992). This study also determined that severance of a stem’s apical tip results in the development
of two or three lateral branches. It is not known to what extent seeds play in spread of this plant, though seeds
have geminated in laboratory conditions (Cemagref, 2004).
Control Methods
In order to achieve eradication, 100% control must be achieved in the first year. Follow up treatments will usually
involved control of seedlings if appropriate, or regrowth from fragments unaffected by herbicides in the first year.
Ludwigia peploides may tolerate low concentrations of residual herbicides (Rejmankova, 1992). Ludwigia has
been used to absorb herbicide residues in runoff water (Bouldin et al. 2006). Suarez et al. (2004) report greater
than 80% control of Ludwigia species in rice crops using the herbicide halosulfuron-methyl. A 75% reduction in
the extent of a Ludwigia infestation in the Laguna de Santa Rosa was been achieved using glyphosate (Pillsbury
2005) and additional herbicides (triclopyr) were used in 2006 to attempt to increase the efficacy (Rose, 2006).
Shading may have potential for small infestations of Ludwigia species; however, large-scale shading operations
may negatively impact other plants, fish, and wildlife (Sears and Verdone, 2005).
Mechanical Methods
The U.S. Army Corps of Engineers (2002) recommends mechanical harvesting, hand-cutting, and rotovation.
However, caution must be made to remove all plant fragments and roots, otherwise reinfestation can occur.
Furthermore, decomposition of crushed or damaged plant material may result in increased nutrient availability
and a reduction in dissolved oxygen (Sears and Verdone, 2005)
Biological Control
Cordo and DeLoach (1982) found that the flea beetle, Lysathia flavipes, caused heavy damage and sometimes
mortality to L. peploides plants in its native Argentina. The adult and larvae feed on, and eggs are laid on, the
leaves of both L. peploides and parrot’s feather, Myriophyllum aquaticum. Based upon field observations and
preference studies using L. peploides, M. aquaticum, and 30 other aquatic plants, Cordo and DeLoach (1982)
suggested that L. flavipes had good potential as a biocontrol agent in the United States and elsewhere and
recommended other studies, e.g., host range, be conducted.
McGregor et al. (1996) report the activity of another Lysathia species feeding on L. grandiflora. Gassmann et al.
also report on the potential of Lysathia flavipes for the control of Ludwigia peploides. Oberholzer et al. (2007)
however sound a note of caution on the use of Lysathia species, saying that they are usually not efficient enough
SID 5 (Rev. 3/06)
Page 6 of 8
feeders to provide long term control of the other host species Myriophyllum aquaticum and have started work on
Listronotus marginicollis weevil. Listronotus elongatus is known to be a potent biocontrol agent of Hydrocotyle
ranunculoides another nuisance aquatic weed species in Europe.
Attempt to eradicate
We used one population in Cadnam in the New Forest for all the following treatments. Data are mean of three
replicate samples taken using a 25 cm 2 quadrat randomly place din the plot. All material (roots and shoots) was
washed and dried to constant weight in a drying oven at 60C for 72 hours before being weighed for dry weight.
We used an approved aquatic formulation of glyphosate containing 360 g/L active ingredient (Roundup Pro
Biactive) applied at 6 l product per hectare, equivalent to 2.16 Kg a.i per hectare in all cases. Glyphosate and
Glyphosate + 2,4-D amine were applied in 2006, and glyphosate and non-oil soya were applied in 2007. 2,4-D
amine and the non-oil soya adjuvant (code name TFWLM1) were both applied at 450 ml/hectare as tank
Table: Dry weight of Ludwigia peploides at Cadnam after treatment with various herbicide mixtures.
Glyphosate + 2,4-D Amine
Glyphosate + non-oil Soya
Control – no treatment
Dry weight at Time 0
(kg m-2)
2.10 ± 0.22
2.05 ± 0.08
2.21 ± 0.13
2.06 ± 0.19
Dry weight at + 21 Days
(kg m-2)
1.15 ± 0.32
0.86 ± 0.11
0.63 ± 0.28
2.35 ± 0.27
Dry weight at + 56 days
(kg m-2)
0.45 ± 0.07
0.63 ± 0.09
0.06 ± 0.03
2.15 ± 0.33
Control of approximately 75% was achieved using glyphosate and glyphosate + 2,4-D amine mixtures. However
control of 97.81% was achieved using the glyphosate and non-oil soya sticking agent. We assume that this is
due to prolonged slow release of the herbicide into the plant, increasing the opportunity for continued inhibition of
appropriate enzyme system targeted by glyphosate.
We had assumed that the addition of 2,4-D amine to the mixture at sub-lethal levels would encourage the uptake
of glyphosate into the plant. While this technique has been shown to be effective on Japanese Knotweed (TCM
personal communication) it does not appear to have any effect on this species.
The non-oil soya sticking agent is not yet registered for use in Europe, but has shown considerable potential in
trials and field use in the USA. We intend to encourage the company to register the product in Europe for the
start of the 2008 spraying season.
References to published material
This section should be used to record links (hypertext links where possible) or references to other
published material generated by, or relating to this project.
Aznar, J-C, Dervieux, A. and P. Grillas. 2003. Association between aquatic vegetation and landscape
indicators of human pressure. Wetlands 23(1): 149-160.
Bouldin J.L., Farris, JL., Moore, MT, Smith, S. and C.M. Cooper (2006) Hydroponic uptake of atrazine and
lambda-cyhalothrin in Juncus effusus and Ludwigia peploides Chemosphere, 6: 1049- 1057
Cordo, H.A. and C.J. DeLoach. 1982. The flea beetle, Lysathia flavipes, that attacks Ludwigia (water
primrose) and Myriophyllum (parrot feather) in Argentina. The Coleopterists Bulletin 36(2): 298301.
Ditomaso, J. M. and E.A. Healy. 2003. Aquatic and Riparian Weeds of the West. Oakland, California:
University of California Agriculture and Natural Resources.
SID 5 (Rev. 3/06)
Page 7 of 8
Dutartre, A. (2004). The invasion of the Ludwigia peploides. Cemagref Research Examples. June 2004.
Cemagref. 12 Sep. 2005.
EPPO (2004) Ludwigia peploides and L. uruguayensis (=L. grandiflora). EPPO Alert List. 6 October 2004.
European and Mediterranean Plant Protection. 12 Sep. 2005.
Fisher, B. 1998. Grower’s Weed Identification Handbook. Oakland (CA): University of California – Division
of Agriculture and Natural Resources. Publication # 4030. p. WI-215.
Gassmann A, Cock M, Shaw R, Evans H (2006) The potential for biological control of invasive alien
aquatic weeds in Europe: a review. Hydrobiologia 570: 217-222
Gleason, H.A. and A. Cronquist. 1991. Manual of Vascular Plants of North-eastern United States and
Canada, Second Edition. New York: The New York Botanical Garden. Pp 313-315.
Grillas, P. 1992. Les communautés de macrophytes submerges des marais temporaires oligohalims de
Camargue. Etude expérimnetale des causes de la distribution des espéces. Ph.D. Dissertation.
University of Rennes I. Rennes, France.
Haragan, P.D. 1991. Weeds of Kentucky and Adjacent States: A field guide. USA: University Press of
Kentucky. Pp. 126-127.
McAvoy, W.A. Non native plants of Delaware. June 2001. Delaware Natural Heritage Program. 1 Oct.
McGregor, MA, Bayne, DR, Steeger, JG, Webber, EC and Reutebuch, E, (1996) The Potential for
Biological Control of Water Primrose (Ludwigia grandiflora) by the Water Primrose Flea Beetle
(Lysathia ludoviciana) in the South-eastern United States. Journal of Aquatic Plant Management,
34: 74-76.
Natural Resources Conservation Service. PLANTS Database. U.S. Department of Agriculture. 12 Sep.
Oberholzer, IG Mafokoane, DL & Hill, MP (2007) The Biology and Laboratory Host Range of the Weevil
Listronotus marginicollis (Hustache) (Coleoptera: Curculionidae), a Natural Enemy of the Invasive
Aquatic Weed Myriophyllum aquaticum (Velloso) Verde (Haloragaceae) (Parrot’s Feather). Water
Research Commission Report No: KV 180/07 ISBN: 978-1-77005-528-5.
Pillsbury, D. (2005) Outbreak of mosquitoes raises possible threat of West Nile Virus. Sonoma West
Times & News. 20 Jan. 2003. Archives. 10 October
Radford, A.E., Ahles, H. E., and R.C. Bell. 1968. Manual of the Vascular Flora of the Carolinas. North
Carolina: The University of North Carolina Press. Pp. 744-745.
Rejmankova, E. 1992. Ecology of creeping macrophytes with special reference to Ludwigia peploides
(H.B.K.) Raven. Aquatic Botany 43: 283-299.
B (2006) Ludwigia war not won
yet. Press Democrat,
Sears, A.L.W. and L.N. Verdone. 2005. Ludwigia hexapetala management plan for the Laguna de Santa
Rosa, Sonoma County, California. California: The Sonoma County Ludwigia Task Force. # 20052010. 23 p.
Suárez, L., Anzalone, A., Moreno, O. (2004) Evaluation of halosulfuron-methyl herbicide for weed control
in rice (Oryza sativa L.) Bioagro, 2004, 16: 173-182
U.S. Army Engineers Research and Development Center. Aquatic Plant Information System. 16 Aug.
2002. U.S. Army Corps of Engineers. 14 Sep. 2005
U.S. Army Engineers Research and Development Center. Noxious and Nuisance Plant Information
System. 16 Aug. 2002. U.S. Army Corps of Engineers. 14 Sep 2005.
SID 5 (Rev. 3/06)
Page 8 of 8