05-11809
Draft EPPO quarantine pest
Version 0
P IAS Point 7.2
Name: Cyperus esculentus
Taxonomic position: Plant Kingdom; Magnoliopsida (formerly angiosperms), Liliidae (formerly monocotyledons) , Areciflorae, Cyperales, Cyperacea.
Common names : Yellow nutsedge (English)
Souchet comestible (French)
Erdmandelgras (German)
Knolcyperus (Dutch)
Mandulapalka (Hungarian)
Bayer computer code : CYPES
: absent.
Cyperus esculentus is a widely distributed old world species that is an invasive weed in almost all temperate and subtropical regions of the world. It is particular to areas with sufficient summer rainfall, or alternatively irrigated farming systems. It does occur in the tropics but has there largely been replaced by its close relative C. rotundus . The species is known as far North as the coastal region of
Alaska (Holm et al, 1977), and has recently penetrated Europe North of the Alps as far as the
Netherlands.
Its distribution to colder regions is limited by the severity of winter (Stoller, 1973). In the Netherlands cold winters cause severe population declines but do not eradicate the species.
In Europe Cyperus esculentus is native to the Mediterranean region and occurs also in Southern
France. Occurrence in Europe North of the Mediterranean is known from Austria, Germany,
Switzerland, Belgium and the Netherlands (Neururer, 1990; Schmitt and Sahli, 1992;). The species is also present in France (Morin and Sombrun 1984) and in Hungary (Dancza et al, 2004)
Because the species got almost out of control in the sixties in the USA most research on its biology and control dates back to the seventies and was done in the USA. The species received comparatively little attention in Europe, with the exception of the Netherlands where it became invasive in the early eighties. In Hungary the species became invasive recently and receives considerable attention as well.
(Dancza,et al 2004)
Cyperus esculentus is a perennial weed in which only tubers survive the off-season (Bendixen, 1973).
A tuber sprouts in spring at approximately the same time as maize crops germinate when temperatures are higher than ca 14 o C. The sprout develops in a basal rhizome growing to the surface
(in the Netherlands tubers were able to sprout and reach the surface from a depth of 40 cm). Just below the surface the rhizome thickens and forms a basal bulb. The basal bulb produces leaves, and later the inflorescences.
Within a few weeks of emergence (in the Netherlands on average three) the basal bulb will produce lateral rhizomes giving rise to new basal bulbs and plants. This process will be repeated during summer. Approximately from mid summer onwards rhizomes will produce new tubers. Both plant and
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tuber production can be prolific. Growing conditions in the United States allow a single plant to produce 1900 new plants and 7000 tubers in a single season (Holm et al, 1977); in the cooler growing conditions of the Netherlands a single bulb still produces over 500 new tubers in a single season
(Groenendael and Habekotté 1988; Habekotté and Groenendael, 1988).
The bulbs survive winter as long as soil temperatures in the relevant soil depths remain above a threshold level. A soil temperature of –10 o C for 24 hours is fatal; soil temperatures of –4 o C have no effect(Stoller 1973). It is remarkable that tubers may become dormant for a period of several seasons
(Stoller and Wax, 1973). The mechanism is poorly understood; but under Dutch circumstances a tiny fraction of an originally large population still sprouted after six years (Rotteveel and Naber, 1993).
Cyperus esculentus is an obligatory cross pollinated species. Since it is also clonal in growth it is not surprising that the usual prolific flowering seldom results in prolific seedset, with the exception of the
North Eastern United States (Justice, 1946)
Yellow nutsedge tubers are a food source for small rodents and birds. The plants are remarkably free from pathogens, though the rust Puccinia canaliculata is known and used in biological control in the
USA (Phatak et al. 1983). This rust is absent from Europe. A cyst nematode, Heterodera cyperii
(Golden et al., 1962) is also absent, and so is the moth Bactra verrutana (Keeley and Thullen 1970) that was unsuccesfully tried in biological control in the USA.
DETECTION AND IDENTIFICATION
Cyperus esculentus is easily identified in the field ( Wills et al., 1980). The plant has the typical threeangular arrangement of all Cyperacea: stems are triangular, and so is the leaf-arrangement. The presence of tubers rules out confusion with practically all other Cyperacea. Only Cyperus rotundus and Bulboschoenus (Scirpus) maritimus have also tubers. Those are in both cases black, covered with roots, often in chains and not edible due to the hard texture and the bad resinous smell and taste.
Yellow nutsedge tubers are light brown, edible with a tasty, nutty flavour, and always grow single at the end of a rhizome.
Tubers Irregularly round brown tuber with scale leaves (cladophyls) at the end of thin rhizomes emerging from basal bulbs. Tubers are small: up to 10 mm.
Leaves grow in three ranks, mostly emerging from the basal bulb, 30-80 cm long, 5-6mm wide, with a prominent mid vein. The top of the leaf is drawn out and narrows one cm before the tip. Leaves are glabrous, as is the anti-ligule that is normally torn.
Flowers arranged in an umbel at the top of a 30-80 cm long culm, subtended by unequal leaflike bracts varying from 5-25 cm long. Spikelets are yellowish brown or straw-coloured, 1-3 cm long, of several flowers, flattened and two-ranked. Stamens three, style three-cleft.
Fruits Achenes three-angled, narrowing gradually from a square shouldered apex toward the base, about 1,5 mm long, brownish grey to brown, covered with very small grains.
Several varieties or biotypes exist and have been described by Ter Borg, (1988); and Horak and Holt
(1986). It should be noted that types sometimes mentioned in the agricultural context of weed science are often confusing.
In Southern Europe a distinct variety with larger tubers on short rhizomes is grown as a horticultural crop under the name “chufa”. Chufa is sometimes sold in other parts of Europe but does not persist under field conditions.
Cyperus esculentus is originally a species of riverbeds that are usually dry in summer and is easily dispersed by (winter) floods. As a weed the species is almost completely confined to agricultural land, and dispersed by human action. Movement of plant propagation material such as bulbs (lilies) and
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corms (gladioli) as well as whole plants (perennial ornamentals and shrubs) is the most important pathway, followed only by dispersion via machinery and soil. Movement through seeds does not seem to be of any importance in Europe, and very limited outside (Horak and Holt, 1986).
In the first years of invasion in the Netherlands the number of infested fields increased greatly through the growing of infested gladioli. (Naber and Rotteveel, 1986)
Economic impact
Yellow nutsedge is a noxious weed and listed by Holm as one of the world’s worst weeds (Holm et al
1977). The economic damage is dependant on a number of agronomic factors that interact:
1. Cropping system . Yellow nutsedge grows most profusely in intensively grown summer crops with an open structure that are well manured and well watered. Damage is small or absent in winter crops like cereals or rape. Damage through competition can be large in sugarbeet or maize and total in crops like gladioli.
2. Produce type . In rootcrops damage tends to be higher because the dense interwoven rhizomes obstruct harvest and increase the cost of cleaning the produce. In extreme cases harvest becomes impossible (sugarbeet, gladioli, lilies). Crops of which only above ground are harvested experience little or no damage from obstructed harvesting operations.
3. Propagation materials . Yellow nutsedge infested land is not suitable for the production of bulbs, tubers, corms or whole plants for use as propagation material. Cleaning is either impossible, or cost prohibitive, or a combination of both.
4. Land value . Severely infested land looses its agronomic value. Several cases are known in the Netherlands where severely infested land was put to forest. In other cases farming shifted from high value flowerbulb production to low value grassland.
5. Phytosanitary measures . The successful elimination of yellow nutsedge from the entire gladioli propagation crop in the Netherlands had a cost of approximately 1.5 – 3 million euro.
The actual damage will always be farm specific. Calculations In the Netherlands showed considerable damage. In 1984 calculations showed that a standard arable farm would face a decrease in saldo from euro 1000 (no infestation) to less than 100 euro per ha per year. The total loss of a flower bulb crop may easily account to over 50.000 euro/ha, not counting the loss of land value that could be estimated to be the same.
Control
Since spread is almost totally by man strict hygienic and preventive measures are both necessary and very effective in order to contain infestations. The Dutch government programme obtained a considerable decrease in dispersal from infested fields.
Control is also possible through the cultivation of crops that are highly competitive and close early (
Keeley and Thullen 1978). Wintercereals, grassleys and especially fibrehemp allowed almost no nutsedge development under Dutch conditions (Lotz et al, 1991). However, even a ten- year period under a grass ley did not eliminate yellow nutsedge (Rotteveel and Naber, 1996)).
Mechanical control gives short- lived positive control effects but should be avoided because of its massive contribution to in-field dispersal. Rhizomes and plants cling to machinery and are in this way dispersed over the field.
Soil fumigation is highly effective, but will seldom eliminate yellow nutsedge. This is even the case for methyl bromide. In the clean up of severe infestations one can make a good start with soil fumigation, especially on very homogeneous well structured, deep soils(Rotteveel and Naber, 1987).
Chemical control is possible, but there are only few effective active ingredients available. Glyfosate is effective but lacks selectivity and persistence. It should be used at double the normal dose. Six applications in a season gave a very high degree of control, but did not eliminate yellow nutsedge
(Keeley et al. 1985; Rotteveel and Naber, 1993)
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S-metolachlor is the most important selective herbicide available but is unfortunately only selective in a few crops. However, in maize it is the basis for highly effective control when lightly incorporated into a moist soil. Bentazone with oil has good contact action, but the effect is short-lived. (Godinho et al.
1984; Rotteveel and Naber, 1986, 1988; Rotteveel et al. 1993). Nicosulfuron has a good effect and is selective in maize; its value in eradication programmes is not known.
One should note that the reason for the increase in importance of nutsedges in the world was the large- scale use of herbicides in agriculture. Practically all herbicides are also selective in nutsedges.
Competing weeds were well controlled and nutsedge could conquer the field. It is very important to choose weed control programmes carefully when yellow nutsedge is present.
Phytosanitary risk
Most of the world already has wide-spread yellow nutsedge infestations, but on a local scale there are many fields still free from this weed. Yellow nutsedge is internationally a non-classified organism without any EPPO status.
However: Europe north of the Alps and Loire is for the greater part still free from yellow nutsedge. The species is well adapted to invading this area and is expected to have a high potential for economic damage to horticulture. The risk of dispersal through the trade in propagation material is large.
None have been identified yet for the EPPO region. Extensive experience with phytosanitary measures against Cyperus esculentus have been obtained in the Netherlands. (Naber and Rotteveel,
1986) and were found to be effective.
These effective measures aimed at containment included the following:

Prohibit import of nutsedge infested propagation material;

Identification of infestations (surveys);

Official declaration of infested status of fields;

Prohibit the use of infested fields for the production of propagation materials other than seed or cuttings;

Destruction of infested propagation material.

Cleaning of machinery used on infested land.
For eradication purposes effective measures did also include:

A ban of growing all rootcrops on all land declared nutsedge infested;

Lifting of the declaration after at least three consecutive seasons without any visually presence of nutsedge.
Control strategy for eradication:
Only maize allows the selective use of herbicides necessary for efficacious nutsedge eradication. Only maize offers also the open crop structure necessary for spot treatments in the last eradication phase.
Control is through S- metolachlor, as early as possible accompanied by spot treatments with glyphosate. In a later phase, when few nutsedge shoots emerge spot treatments alone can be used.
However, almost total general weed free conditions are necessary to work effectively, and the duration of the eradication period might be approximately 20 years in case of heavy infestations.
Bendixen, L.E. 1973
Anatomy and sprouting of yellow nutsedge tubers. Weed Science, 21- 6, p 501503
Borgh, S.J. ter; de Nijs,L.J.; van Oene, H, 1988
Intraspecific variation of Cyperus esculentus in the Netherlands; a preliminary report. VIIe colloque international sur la biologie, l écologie et la systematique des mauvaises herbes,
Dijon. 181- 185
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Dancza,I, Pathy Hofmann, Z, Doma, C, 2004
Cyperus esculentus (yellow nutsedge)- a new weed in Hungary. Zeitschrift für
Pflanzenkrankheiten und Pflanzenschutz, Sonderheft XIX, 223-229 (2004), ISSN 0938-9938
Godinho, I, de Pinho, C.; Leitao, A., 1984
Essais de lutte chimique contre les souchets ( C. rotundus et Cyperus esculentus L.) dans la culture de maïs au Portugal. Proceedings 3rd symposium on weed problems in the
Mediterranean Area: 261-270
Golden, A. M; Rau, G.J and Cobb, G.S. 1962
Heterodera cyperi (Heteroderidae), a new species of cyst-forming nematode. Proceedings of the Helminthological Society 29- 2: 168- 173
Groenedael, J.M. van; and Habekotté, B., 1988
Cyperus esculentus L:.- biology, population dynamics and possibilities to control this neophyte. Z. PflKrankh. PflSchutz, Sonderheft XI,61-69
Habekotté, B. and Groenedael, J.M. van, 1988
Population dynamics of Cyperus esculentus L. (Yellow nutsedge) under various agricultural conditions. Med. Fac.landbouww. Rijksuniv. Gent 53(3b): 1251-1260.
Holm, Le Roy G, Plucknett, D,L, Pancho, J.V and Herberger, J.P. 1977
The Worlds worst weeds, ISBN 0-8248-0295-0 University Press of Hawaii, p 125.
Horak, M.J and Holt, J. S., 1986
Isozyme variability and breeding systems in populations of yellow nutsedge ( Cyperus esculentus L)
Weed Science 34: 358-543
Justice, O.L., 1946
Seed production, viability, and dormancy in the nutgrasses Cyperus rotundus and C. esculentus . Journal of agricultural research 73. November 15: 303-317, Washington D.C.
Keeley, P.E., Carter, C. H. and Thullen, R, J. 1985
Influence of glyphosate on resprouting of parent tubers of Cyperus esculentus . Weed Science
34: 25-29
Keely, P.E. and Thullen, R.J. 1970
Biological control studies on yellow nutsedge with
Weed Science 18, no 3: 393- 395
Bactra verutana Zeller.
Keely, P.E. and Thullen, R.J. 1978
Light requirements of yellow nutsedge ( Cyperus esculentus ) and light interception by crops.
Weed Science 26: 10- 16.
Lotz, L.A.P., Groeneveld, R.M.W., Habekotté and Oene, H. van, 1991
Reduction of growth and reproduction of Cyperus esculentus by specific crops. Weed
Research 31: 153-160
Morin, C and Sombrun,F. 1984
Lutte contre le souchet comestible ( Cyperus esculentus L ) dans le maïs en France.
Proceedings of the 3rd symposium on weed problems in the Mediterrenean area 271- 276
Naber, H and Rotteveel A.J.W., 1986
Legal measures concerning Cyperus esculentus L. in the Netherlands.
Med.Fac.landbouww. Rijksuniv. Gent, 51(2a): 355-357
Naber, H and Rotteveel A.J.W., 1986
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Cyperus esculentus ; its build up and methods of control in the Netherlands. Proceedings 49 th winter congress of the Institute International de recherches betteravieres.
Neururer. H., 1990
Einschleppung eines neuen Unkrautes beim Bau einer internationalen gasleitung am beispiel von Cyperus esculentus und möglichkeiten zur raschen sanierung. Z. Pflkrankh.Pflschutz,
Sonderheft XII 71-74.
Phatak, S.C. Sumner, D.L. Wells, H. D. Bell, D.K., and Glaze, N.C. 1983
Biological control of yellow nutsedge with the indigenous rust fungus Puccinia canaliculata.
Science 219: 1466-1447
Rotteveel, A.J.W. and Naber, H, 1986
Chemical control of Cyperus esculentus in maize under Dutch conditions. Med. Fac.
Landbouwwet. Gent 51(2)a: 359-367.
Rotteveel,A.J.W and Naber, H. 1987
The use of soil fumigation against yellow nutsedge. Med. Fac. Landbouww.Rijksuniv. Gent 52
(3b) 1207-1211
Rotteveel, A.J.W. and Naber, H, 1988
Changes in the chemical control of yellow nutsedge ( Cyperus esculentus L ) in maize. Med.
Fac. Landbouwwet. Gent 53(3b): 1241-1249.
Rotteveel, A.J.W and Naber, H. 1993
Decline of yellow nutsedge ( Cyperus esculentus ) when tuber formation is prevented. Brighton
Crop Protection Conference- weeds: 311- 316
Rotteveel, A.J.W, Straathof H.J.M and Naber, H. 1993
The decline of a yellow nutsedge ( Cyperus esculentus L .) population under three chemical management systems aimed at eradication Med. Fac. Landbouww.Univ Gent, 58(3a): 893-900
Rotteveel, A.J.W. and Naber,H. 1996
Persistence of yellow nutsedge ( Cyperus esculentus L) over a ten year period in a grass ley.
Xe colloque international sur la biologie des mauvaises herbes, Dijon: 51-56
Schmitt, R and Sahli, A, 1992
Eine in der Schweiz als Unkraut neu auftretende Unterart des Cyperus esculentus L.
Landwirtschaft Schweiz Band 5 (6) 273- 278.
Stoller, E.W., 1973
Effect of minimum soil temperature on differential distribution of Cyperus rotundus and C, esculentus in the United States. Weed Research 13, 209- 217.
Stoller E.W. and Wax, L.M., 1973
Yellow nutsedge shoot emergence and tuber longevity. Weed Science 21 (1) 76-81
Wills, G.D., Hoagland, R.E. and Paul, R.N., 1980
Anatomy of yellow nutsedge (Cyperus esculentus) Weed Science 28: 432-437.
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