Yellow nutsedge:
early detection – sustainable control
Leaflet
Authors: Martina Keller, René Total, Christian Bohren und Brigitte Baur
Yellow nutsedge has become a difficult to control weed in several regions of Switzerland for the last years. It is easily spread by several means of dispersal. It propa- gates especially well in row crops and crops of limited competitiveness such as vegetables. Yellow nutsedge causes considerable yield losses. The control is highly challenging. In heavily infested fields the extinction or at least the reduction to a steadily low infestation level of yellow nutsedge will take years. Therefore, prevention is better than cure!
Distribution and relevance
Yellow nutsedge (Cyperus esculentus) is widely distributed on all continents – originally it was distributed mainly in warmer regions. In the meantime it is also found in temperate regions with colder climate. In Switzerland it is mainly found on agricultural land.
The cultivar group of yellow nutsedge (chufa) is grown in Europe in Spain in the Province of Valencia. The tubers are the harvested plant parts. Focus of this leaflet is the weed of yellow nutsedge which differs from chufa in several aspects.
For example the weedy cultivar is frost tolerant whereas chu- fa is not.
Yellow nutsedge was observed for the first time in Switzer- land about 30 years ago. Meanwhile it has become a serious problem in Ticino, in Eastern Switzerland (SG, TG, ZH), in Oberaargau (BE), in Seeland (BE, FR), in Orbeebene (VD) and in Chablais (VD, VS) In other cantons yellow nutsedge occurrence and/or abundance is still very low or it is not found at all. However it is highly likely that many more fields are affected than it is currently known. In addition area of infested fields will still increase as the tubers are easily spread with machinery and with other means of dispersal (see below).
Identification
Yellow nutsedge belongs to the Cyperaceae family. Members of this family often have a triangular stem, without nodes.
Leaves are also arranged triangularly (120°). Cyperaceae differ morphologically from the family of Poaceae. The classi- cal graminicides do not control yellow nutsedge.
There are several Cyperaceae which are difficult to control.
Some form tubers or rhizomes and runners. Without inflo- rescence, it is difficult to identify the species.
Abbildung 2: Erdmandelgrasblüte (Foto C. Bohren)
Figure 2: Below ground the yellow nutsedge forms rhizomes and new tubers. (picture C. Bohren).
Figure 1: Yellow nutsedge inflorescence (picture C. Bohren).
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Identification of Yellow Nutsedge
Stem triangular
filled
no nodes
glabrous
leaves at the base of the stem
height 30-70 cm
Leaves cross-section V-shaped
triangular arrangement
glabrous
brilliant
yellow to bright green Inflorescence
(Figure 1)
terminal with yellowish brown spikelets
Below ground (Figure 2)
Plants originating from one tuber are connected via rhi- zomes.
white/brown rhizomes
rhizomes may form a dense network
tubers ( 2 - 12 mm) are formed at the ends of rhi- zomes
Carex hirta is often confounded with yellow nutsedge. How- ever, as indicated by the name it is hairy and forms below ground runners and no tubers. Newly found Cyperaceae are posted on
http://www.agroscope.admin.ch/gemuesebau/07296/index.ht ml?lang=de and www.infoflora.ch.
Life cycle
Under northern European conditions, propagation of yellow nutsedge is almost exclusively vegetative via the formation of tubers. The tuber sprouts and a basal rhizome grows towards the soil surface. A basal bulb is formed close to the soil sur- face. A tuber can form several sprouts (Figure 3 and 4).
From this basal bulb a new plant (Figure 3) with several leaves is built. After a short time new rhizomes grow from the basal bulb and new basal bulbs are formed at their ends. The formation of new tubers starts in early summer and lasts until the first frosts. From one “mother” tuber several hundred tubers can be formed during one vegetation period. Thus, a few tubers suffice to rapidly colonize a field.
The onset of tuber formation depends on external conditions and varies considerably. Most tubers are formed in the upper soil layer (0 to 20 cm). Depending on soil type single tubers can be found down to a depth of 50 cm. The aerial parts of the plant and the rhizome die off in fall. The tubers overwinter and sprout relatively late in the season at higher soil tempera- ture. Some tubers become dormant and can sprout after years.
The measures described below are based on literature, ex- pert knowledge, findings of Agroscope, the cantonal agricul- tural administration organized in the working group „Erdman- delgras“(PAG-CH) (yellow nutsedge) of the platform Acker- bau (arable farming).
Prevention
Once established, yellow nutsedge is very difficult to control.
Thus, farmers and vegetable growers must do everything to stop the dispersal of yellow nutsedge to other fields.
Tasks:
Neither planting material, nor soil, nor remains of har- vested crops should be transferred from infested fields to other fields.
After working in an infested field, machinery and equip- ment need to be cleaned on-the-spot.
Special attention should be given to the thorough clean- ing of wheels, tires and machinery.
Infested fields need to be managed (cultivated, harvested etc.) last.
Agricultural contractors need to be informed so they can plan their working schedule accordingly.Figure 3: Emerging yellow nutsedge plants. Even at this early developmental stage, the characteristic bright yellowish green colour is clearly noticeable. (picture M. Keller).
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Control of early infestation with patches limited in size and number
If tubers were brought to a new field, early detection before tuber formation, which starts in early summer, is crucial. Few plants or small patches of yellow nutsedge can be eradicated with moderate effort at that stage. If infestation is discovered at a later stage and tuber formation already occurred once or over more seasons, the dimension of the problem has multi- plied as well.
Tasks:
Generously excavate soil from infested spots (plants, tuber and infested surrounding soil, also beneath plowing level).
Excavated material needs to be correctly disposed of:Small amounts can be disposed of with regular house- hold waste (assuming and requiring that it will be inciner- ated). Cantonal administration should be contacted if larger amounts need to be disposed.
After excavating, the spots should be clearly marked and the exact location should be recorded to facilitate moni- toring of possible re-emerging plants.
Excavated, previously infested spots should be excluded from harvest and soil cultivation or should at least be managed separately. These actions minimize the risk of spreading of the tubers which were missed by previous excavation.
It is advisable to let small infested areas rest. Newly emerging yellow nutsedge plants can then be detected more easily.
If patches with yellow nutsedge or suspicious patches have been found in a field, one should contact the can- tonal administration. They are experienced in the control and handling of infested fields and can provide infor- mation about possible control strategies.
If there are several, larger infested spots, there is also the possibility of soil steaming. Agroscope tested a steaming device of the company „Möschle Seifert Dämpftechnik und Dampfsysteme“ and achieved good results. Steam is brought into the soil by 30 cm long in- jectors. 30 cm corresponds to the normal ploughing depth in Switzerland. Protocol: The upper 30 cm of soil were kept at high temperatures of 80 to 90°C for about 15 minutes. However, tubers below 30 cm were not con- trolled with this method.
Do not only watch the detected spots, but keep an eye on the whole field for newly emerging yellow nutsedge plants.
Please report infested fields to info flora http://www.infoflora.ch/ (only for Switzerland). This helps watching the spread of yellow nutsedge in Switzerland.Eradication at the field level –approaches
In heavily infested fields, eradication or at least the reduction to a steadily low infestation level is time consuming, requires endurance and asks for an integrated approach (crop rota- tion, combination of chemical and mechanical control measures). The formation of new tubers needs to be sup- pressed at all cost. Agroscope has carried out field trials to test different options to reduce infestation levels and, in the long run, to eradicate yellow nutsedge in heavily infested fields.
Adapting the crop rotation
As a first step, farmers or vegetable growers need to exclude potatoes, sugar beet and vegetables (especially vegetables belonging to the root crops) from the crop rotation of highly infested fields. The low density of the crop stand, the open canopy at early growth stages provide optimal conditions for yellow nutsedge (Figure 5). Growing rhizomes, which pene- trate the potatoes and the root body of vegetables can cause additional damage. Furthermore the risk of further dispersal of yellow nutsedge with harvest equipment is very high.
The implementation of cereal and fodder crop based crop rotations seems to be the best way to reduce infestation and, ideally, eradicating yellow nutsedge within a field. Further- more the risk of further dispersal is greatly reduced. Important is the consequent, intensive control of yellow nutsedge in each crop and over the whole crop rotation. To let the field rest for one year, may be advisable as it allows an intensive control and good monitoring of yellow nutsedge pressure in the first year.
Figure 4: From one tuber several sprouts can emerge.
Up to 5 sprouts were observed (picture M. Keller).
Figure 5: Heavily infested carrot field. The yellow nutsedge is already flowering (center, top right) (picture R. Total).
4 Maize
Several herbicides with a partial efficacy against yellow nutsedge are registered in Switzerland (Figure 6, comment for English version: halosulfuron-methyl is currently not regis- terd for use in Switzerland). Maize is therefore a suitable crop for an eradication programme. In order to time the develop- ment of maize and thus the herbicide application with the germination of yellow nutsedge, sowing should be delayed and take place between early May and mid of May. Herbicide application of foliar active herbicides needs to be carried out at an early growth stage (2 to 3 leaf stage) of yellow nutsedge.
At this early stage, efficacy is highest.
As emergence of yellow nutsedge is scattered, herbicide application should be splitted. A combination of herbicides each exhibiting partial efficacy increases overall control. The plant architecture of yellow nutsedge with its erect and thin leaves and waxy leaf surface require addition of a spreader to the herbicides applied Post-Emergence. The sulfonylurea herbicides registered for use in maize are partly effective, but efficacy varies between active ingredients. The traditional maize herbicides from the triketone family have a medium effect, but the effect is short-lived.
In the trials carried out by Agroscope at two sites during two years a split application of Titus (active ingredient: rimsulfu- ron) and Callisto (active ingredient: mesotrione) showed a good control of yellow nutsedge. Efficacy of the treatment was increased when followed by below canopy application of Basagran (active ingredient: bentazon) at late emerging yel- low nutsedges. Small patches can also be controlled later with a backpack sprayer (e.g. also with bentazon).
Mechanical weed control is effective as well. Repeated hoe- ing controlled yellow nutsedge well between the rows. In the intrarow area yellow nutsedge is not controlled and thus the crop is weakened and new tubers are built. For example, the application of Dual Gold (active ingredient: S-Metolachlor) after sowing combined with hoeing twice thereafter had a good effect. For optimal efficacy soil must be sufficiently hu- mid.
Artificial meadows
In sown grass clover crops, the risk of further tuber dispersal is marginal. In vigorous, dense clover grass stands with in- tensive management (several cuts and regularly fertilized) the formation of tubers is strongly reduced or even suppressed. If the sward is damaged for example by mice or grazing cattle yellow nutsedge sprouts and fills the space quickly. Neverthe- less a grass clover crop over several years may be suited for a field (heavily) infested with yellow nutsedge.
Cereals
Thick vigorous crop stands suppress the late germination of yellow nutsedge. However, during crop ripening sufficient light reaches the soil and the yellow nutsedge starts germina- tion and growing. Thus, after harvest an intensive mechanical stubble treatment is crucial. The success thereof depends on the weather and the onset of tuber formation in the respective field. An application with glyphosate shows some effect but resprouting occurs.
Figure 6: High yellow nutsedge pressure in the untreated control, in the herbicide treatments pressure is much lower.
(trial 2012) (picture R. Total).
Conclusions
Integrated control strategies are necessary to stop the further spread of yellow nutsedge. Especially the dispersal by machinery, equipment, contaminated soil etc. must be impeded.
If yellow nutsedge is transported accidentally to a new field, early detection and eradication in the field are cru- cial. Further monitoring of the detected spots and of the whole field as well as excluding the infested area from soil cultivation are very important.
In fields regularly cropped with vegetables, a shift of the crop rotation towards cereals and fodder crops must be considered.
On infested fields neither potatoes nor sugar beet should be cropped. The risk of further spreading and yield loss (qualitative and quantitative) is too high.
Crops such as maize, cereals or intensively managed artificial meadows are better suited for heavily infested fields. Because control measures are available in these crops and they are competitive.
In maize, yellow nutsedge can be controlled rather effec- tively with herbicides or hoeing or a combination of the two. In cereals an intensive mechanical stubble treatment is an important control component. Formation of new tubers must be suppressed.
In heavily infested fields it might be advisable to let the field rest for one season, allowing regular chemical and mechanical control measures and a monitoring.
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Further information and references
Baltisberger, M. 2003: Systematische Botanik – Einheimische Farn- und Samenpflanzen. Vdf Hochschulverlag AG an der ETH Zürich.
Bohren C. and Neuweiler R., 2011: Erdmandelgras-Lebenszyklus.
Bohren C. and Wirt J., 2013: Aktuelles zu Erdmandelgras (In preparation).
Bundesamt für Naturschutz. Cyperus esculentus (Cyperaceae), Erdmandel:
http://www.floraweb.de/neoflora/handbuch/cyperusesculentus.html, assessed 29.04.2013.
EPPO. Cyperus esculentus: http://www.eppo.int/QUARANTINE/Pest_Risk_Analysis/PRAdocs_plants/draftds/05- 11809%20DS%20cyperus%20esculentus.doc., assessed 19.06.2013.
Lauber K., Wagner G. and Gygax A., 2012: Flora Helvetica, 5. Auflage Haupt Verlag Bern-Stuttgart-Wien.
info flora, Das nationale Daten- und Informationszentrum der Schweizer Flora.
http://www.infoflora.ch/de/assets/content/documents/neophyten/inva_cype_esc_d.pdf, assessed 06.08.2013.
http://www.extension.org/pages/66868/weed-profile:-yellow-nutsedge-cyperus-esculentus-and-purple-nutsedge-c-rotundus assessed 21.05.2013.
De Vries F. T., 1991. Chufa (Cyperusesculentus, Cyperaceae): A Weedy Cultivar or a Cultivated Weed? Economic Botany 45(1), 27-37.
Korres , N. E.; 2005. Encyclopaedic Dictionary of Weed Science: Theory and Digest. Intercept Limited, Andover, Hamp- shire.
Neuweiler R., Bohren C. and Total R., 2011: Erdmandelgras – Handeln bevor es zu spät ist.
Neuweiler R. and Total R., 2012: Mit Kräften gegen das Erdmandelgras. Bauernzeitung (14), 31.
Neuweiler R. and Total R., 2012: Erdmandelgras – ein Eindringling: Ein Problemunkraut auf dem Vormarsch. BWagrar (16), 17-18.
Neuweiler R. and Total R., 2012: Bekämpfung von Erdmandelgras ist anspruchsvoll. Der Gemüsebau/Le Maraîcher (1), 40- 40.
Neuweiler R. and Total R., 2013: Erdmandelgras: Wehret den Anfängen. Landfreund (1), 32-34.
Neuweiler R. and Total R., 2013: Mit vereinten Kräften gegen das Erdmandelgras. Gemüsebau Info. (7).
Riemens M. M., van der Weide R.Y. and Runia W.T., 2008. Nutsedge Biology and Control of Cyperus rotundus and Cyperus esculentus, review of a literature survey. Plant Research International B.V., Wageningen, PPO report 3250100200, PRI report 3310307708.
Schmitt R. and Sahli A., 1992. Eine in der Schweiz als Unkraut neu auftretende Unterart des Cyperus esculentus L.. Land- wirtschaft Schweiz Band 5 (6), 273-278.
Strickhof: http://www.strickhof.ch/fachwissen/pflanzenschutz/erdmandelgras/ zuletzt besucht am 21.05.2013.
Total R., 2005. Erdmandelgras, ein wiederentdecktes Problemunkraut. Der Gemüsebau/Le Maraîcher 4/2005, 12.
Total R., Neuweiler R., Bohren C., Baur B. and Streit B., 2008. Erdmandelgras - ein Problemunkraut auf dem Vormarsch.
Merkblatt Agroscope Changins-Wädenswil ACW.
USDA Plant Guide Purple Nutsedge. http://plants.usda.gov/plantguide/pdf/pg_cyro.pdf assessed 21.05.2013.
Waldispühl S., Stamp P. & Streit B., 2007. Optimierung von Bekämpfungsstrategien gegen das Knöllchen-Zypergras (Cy- perus esculentus L.). Diplomarbeit ETH.
Schonbeck, 2013. Weed Profile: Yellow Nutsedge (Cyperus esculentus) and Purple Nutsedge (C. rotundus), http://www.extension.org/pages/66868/weed-profile:-yellow-nutsedge-cyperus-esculentus-and-purple-nutsedge-c- rotundus#.UgC_4ayO58E, assessed 06.08.2013.
Plattform Ackerbau PAG-CH, Erdmandelgras, http://www.pag-ch.ch/de/arbeitsgruppen/souchet-comestible/ assessed 06.08.2013.
http://threeissues.sdsu.edu/three_issues_coquillofacts05.html, assessed 19.06.2013.
Impressum
Version: August 2013 Herausgeber: Agroscope
Schloss 1, Postfach 8820 Wädenswil www.agroscope.ch Copyright: Agroscope
