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” العشب األكثر سوء عالميا ” السعد

Cyperus rotundus

“the world's worst weed”

Infrastructure & Municipal Assets Sector

Parks Recreation Facilities (PRFD)

December 2010

Dr.AbdulSattar S. Al Mashhadani

Landscape Expert

Weeds are plants that alter the structure of natural

communities, interfere with the function of

ecosystems, or have negative effects on humans,

agriculture, or other societal interests.

About 8000 species, or approximately 3% of the

total number of plant species worldwide, have been

documented as weeds.

Of these, about 200 species, less than 0.1% of the

world’s flora, account for approximately 95% of weed

problems in agriculture

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Cyperus rotundusالسعد

purple nut sedge, coco-grass, red nut sedge

Cyperus rotundus L.

Family: Cyperaceae

Genus: Cyperus

Species: rotundus

Synonym(s):

Cyperus olivaris O.Targ.Tozz.

Pycreus rotundus (L.) Hayek

36 genera in Cyperaceae,128

species in Cyperus

Commonly known as nutgrass .

This is a Rhizome perennial plant and a species of sedge

(Cyperaceae) native to Africa, southern and central Europe

(north to France ,Austria, South of Ukraine) and Balkan

Peninsula, western and eastern Mediterranean, southern and

Middle Asia (except northern districts). tropical Arabia, North

and Southern America, Australia.

Nutsedge is among the most difficult

weeds to control and can rapidly

colonize turf, ornamental areas,

pastures, and cultivated fields

Cyperus rotundus

It is a highly competitive plant because of its

upright growth habit, rhizomatous root system,

and rapid growth.

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Cyperus rotundus is one of the most invasive weeds known, having spread out to a worldwide

distribution in tropical and temperate regions. It has been called "the world's worst weed" as it is

known as a weed in over 90 countries, and infests over 50 crops worldwide.

In the US it occurs from Florida north to New York and Minnesota and west to California and most of

the states in between.

Similar Species

Cyperus esculentus L.

Yellow nutsedge (Cyperus esculentus L.) is an

aggressive perennial plant that is native to North

America and Eurasia.

It is a problem weed in field crops throughout the United

States.

This weed thrives in low, damp soils, but is also

troublesome in cultivated fields and pastures of all soil

types.

Despite its widespread presence, yellow nutsedge can

be effectively managed with a consistent integrated

control program that combines cultural, mechanical,

and chemical methods.

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- Yellow nutsedge primarily reproduces by means of tubers.

- One plant can produce several hundred to several thousand tubers during a single

growing season.

- The plant’s tubers break out of dormancy in winter and begin to germinate in the

spring.

- Each tuber has several buds or‘eyes’ that can produce two or three sprouts or plants.

- Each new plant can eventually grow up to 75 cm in height and is topped by a cluster of

straw-colored seed heads (inflorescence).

- The clusters, which resemble bottle brushes, form at the top of the central stalk about

two months after plant emergence.

- Mature yellow nutsedge can produce hundreds of millions of seeds per acre.

- The viability of a mature seed is relatively low, ranging from 5 to 40 percent.

- Seed germination and seedling survival are highly dependent on favorable

environmental conditions, and seedlings often perish due to their small

size and lack of vigor.

YELLOW NUTSEDGE Cyperus esculentus L. var.

leptostachyus Boeckl.

Cyperus esculentus :

Yellow nutsedge grows from 30cm to 80 cm in height and produces yellowish-brown flowers;

Purple nutsedge grows 30 cm to 60 cm in height and produces purple to brown flowers .

Some USA states reports citing nutsedges do not always differentiate between the two. The two

species may be found growing in mixed stands and are difficult to distinguish before flowers

appear.

Usually yellow nutsedge is found on low, moist areas, while purple nutsedge is found on well-

drained soils . Under optimum growing conditions, purple nutsedge is more vigorous and

competitive than yellow nutsedge .

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Cyperus rotundus is found in cultivated fields, farmlands, neglected areas, wastelands,

grasslands, at the edges of forests, and on roadsides, sandy or gravelly shores,

riverbanks and irrigation canal banks.

The plant is found in locations receiving full sunlight that provide enough water and

nutrients to sustain its growth (Its growth is severely restricted by shade).

It is predominant in disturbed areas and lawns/turf. It is a major agricultural and garden

weed but only a minor weed in other respects ???

- Purple nutsedge grows well in almost every soil type, over a wide range of soil

moisture, pH and elevation.

- It is encouraged by frequent cultivation and grows best in moist fertile soils .

- In cool or waterlogged soils it grows slower, flowers little and produces fewer tubers .

- It is less tolerant of low temperatures and shaded areas than yellow nutsedge .

- Purple nutsedge is relatively sensitive to cold and is restricted to latitudes where the

average minimum air temperature for January is higher than -1°C .

It's habitat description

- Researchers reported that purple nutsedge grows best where soil moisture is high, such

as in upland rice and sugarcane culture and consequently is not an important weed of arid

regions, except on irrigated land .

- Travlos and colleagues (2009), however, claim that purple nutsedge is one of the most

serious weed problems of the arid and semi-arid environments.

- It is one of the most common weeds of the secondary succession occurring in abandoned

and dry fields of arid environments .

It's habitat description

Its existence in a field significantly reduces crop yield, both because it is a

severe competitor for ground resources, and because it is allelopathic, the

roots releasing substances harmful to other plants. Similarly, it also has a bad

effect on ornamental gardening.

The difficulty to control it is a result of

its intensive system of underground

tubers and its resistance to most

herbicides,

It is also one of the few weeds

that cannot be stopped with

plastic mulch .

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Purple nut sedge 's features

The plant has slender leaves that are connected to a network of

underground stems (rhizomes), roots, and tubers.

Although It's flowers profusely if not mowed, very few seeds are formed,

and few of them can reproduce. Thus seeds are not often the source of

new purple nutsedge plants.

The underground tubers and corms (the “nuts” or “nutlets”) are the

primary source of purple nutsedge infestations.

Some tubers are linked to aboveground growth, but other tubers may

not be connected to leaves aboveground.

Left undisturbed, purple nutsedge will spread by growing laterally

underground, spreading several meters each year.

New infestations of purple nutsedge occur when tubers are moved from

one area to another in soil, plant containers, or on equipment.

Under optimum conditions, a network of nutsedge plants arising from

one tuber can produce 100 or more tubers in about 100 days. About

80–95 percent of the tubers are located within the top 15 cm(6 inches) of

soil. However, tubers have been reported to be present as deep as 45 cm

(18 inches).

It's features

Once tubers form, they can remain viable in soils for at least two years if they retain

moisture . They can survive even when soils are very dry for short periods.

However, if tubers are brought to the soil surface for about 1 week under sunny conditions,

they dry out and die.

Populations of viable purple nutsedge tubers can be dramatically reduced by repeatedly

turning the soil at 1–2-week intervals to expose the tubers to the sun.

Tuber dormancy is perhaps the most important adaptation that enables purple nutsedge to

persist in turf and ornamental areas.

Dormancy prevents tubers in the soil from sprouting all at once, so a potential reservoir for

new plants is maintained. This is the reason purple nutsedge will emerge after herbicide

applications or hand weeding.

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Weed pulling in gardens usually results in breakage of roots, leaving tubers in the

ground from which new plants emerge quickly. Ploughing distributes the tubers in the

field, worsening the infestation; even if the plough cuts up the tubers to pieces, new

plants can still grow from them.

Most herbicides may kill the plant's leaves, but most have no effect on the root

system and the tubers. In addition, the tubers can survive harsh conditions, further

contributing to the difficulty to eradicate the plant.

In agricultural fields, both purple and yellow nutsedge species reproduce primarily by

underground tubers. Management of nutsedges should focus on depleting tuber reserves

and suppressing tuber multiplication .

Manual Control: Approximately 95% of purple nutsedge tubers are confined to the top 12

cm of soil, making shallow tillage an effective method of reducing tuber multiplication.

Tillage should be done at frequent intervals (eg: three weekly).

When hand-weeding, the wiry connections between tubers make them easier to remove

Specially in sandy or loamy soil ) than if the connections have been severed by soil cultivation.

The tuber, or basal bulb, of an emerged shoot must be removed to control purple nutsedge.

Simply removing the top growth is ineffective, and an inch or so of new growth will emerge

the following day. Patient gardeners can dig up and remove tubers from the soil to greatly reduce

purple nutsedge populations; however, a few missed tubers will maintain the infestation, and

another weeding cycle will be required in a few years.

Physical control: Nutsedges are capable of penetrating mulch with a thickness of four times

that currently used in commercial vegetable production. Plastic mulches are used in commercial

vegetable gardens for suppressing weeds by providing a physical barrier . Soil solarization, a

method of increasing soil temperature using polyethylene mulch, has proved effective

against many weeds when using clear film .

Management information- Cultural control methods

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Cultural control methods - Mulching ornamental areas

Purple nutsedge will not be controlled with organic mulches. Sheet mulches also are

ineffective against this species. Black plastic sheet mulch is not effective because the sharp,

pointed shoot tip of the purple nutsedge plant can easily penetrate it. The thin mulch used in

pineapple fields is a barrier to water evaporation but not to purple nutsedge. Even thicker sheet

plastic mulch materials are readily penetrated. Probability of penetration increases when the

plastic mulch materials are spread tightly over the soil surface or settled against the soil surface by

rain puddles, additional soil, or other some other object.

Weed cloth, or woven black polypropylene weed mat, can be effective in suppressing purple

nutsedge when used properly.

It is porous to air and water and can be an effective tool for reducing underground tubers without

the use of chemicals or tedious hand-weeding.

It is a very durable material that can be re-used many times if handled carefully to avoid making

holes by tearing.

Cultural control methods - Mulching ornamental areas

Using weed cloth against purple nutsedge requires that the garden area be fallow (not

planted or tilled) for a period of 2–4 months. After the last crop is harvested, remove all plant

residues by mowing or rototilling, and cover the planting area with the weed cloth. The method of

securing the cloth to the soil is crucial in preventing purple nutsedge penetration through the weed

cloth. The preferred securing method is to use long (25-30 cm ) spikes fitted with a large flat

washer. These spikes secure the weed mat to the ground but should not be used to pull the weed

mat too tight. There should be enough slack to allow some air space between the soil and the weed

mat.

The worst way to secure the weed mat is to use rocks, soil, or other heavy objects. When

the weed mat is held tightly to the ground, purple nutsedge shoots can push through the

fabric.

With the weed mat properly in place, purple nutsedge is induced to sprout by generous and

frequent watering. A new weed mat tends to repel water, but after a 2–3-week exposure to

full sunlight, shrinkage occurs and water can pass through the material. As the purple

nutsedge germinates, it pushes the weed mat upward, as if it was inflating it. The purple

nutsedge grows so fast that when the pointed tip of the leaf blade gets caught in the weave

of fabric, the rapidly elongating leaf blade starts to crinkle up behind it, and penetration of

the cloth is thus prevented.

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Cultural control methods - Mulching ornamental areas

The weed mat must remain in place long enough for weeds to germinate below it and die

from lack of sunlight.

After several cycles of weed growth and die-back during the 2–4-month period, the weed

mat can be removed and the garden replanted. Most of the weed propagates (including

purple nutsedge tubers) will have tried to emerge and died.

When the plastic is removed, it is important not to disturb the soil unnecessarily. Cultivation

brings up lower layers of soil that will likely contain viable weed seeds and purple nutsedge

tubers. Mulching the soil surface after removing the weed cloth will help to suppress any

weed seeds remaining in the soil and slow nutsedge germination by preventing increases in

soil temperature.

Cultural control methods - Chemical control methods

Non-selective herbicides

Non-selective herbicides are an option for controlling purple nutsedge in ornamental areas. One of

the most effective herbicides for non-selective control of purple nutsedge is glyphosate (several

products with this active ingredient are commercially available).

Glyphosate is translocated throughout the entire plant, allowing it to eradicate the underground

tubers connected to the leaves. Timing of glyphosate applications is critical.

To obtain maximum control, purple nutsedge flowers should be present before herbicide

application(Photo). Translocation throughout the plant is limited before floral emergence, and the

herbicide will only eradicate top growth and not existing underground tubers. Apply glyphosate 2–3

months after the initial emergence of purple nutsedge. This will eradicate all underground tubers

connected to the emerged purple nutsedge shoots, as well as the original tubers that sprouted. The

purple nutsedge population will be greatly reduced, but it is unlikely that this procedure will

eradicate the entire purple nutsedge stand. Tubers that are dormant or not connected to

aboveground leaves will not be affected, as glyphosate is de-activated once it comes into contact

with the soil. If purple nutsedge continues to be a serious problem, repeat this procedure

accordingly. Glyphosate can also be used as a spot treatment in both turf and ornamental areas.

Special care must be taken to avoid getting glyphosate spray or drift on green bark or foliage of any

desirable surrounding plants, as it is a non-selective herbicide

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Cultural control methods - Chemical control methods

Selective herbicides

There are many selective herbicides that can be used effectively to control purple nutsedge in warm-

season turfgrasses. Herbicide applications are most effective when applied to purple nutsedge plants

having at least three to eight leaves.

SedgeHammer® (halosulfuron, formerly marketed as Manage®) provides effective control of purple

nutsedge and can be safely applied to most warm-season grasses.

Applications of Certainty® (sulfosulfuron) and Monument® (trifloxysulfuron sodium) are also effective

against purple nutsedge.

Applications of MSMA are effective against purple nutsedge.

Consult product labels for specific information on turf grass tolerance.

Apply Suggested application rates for these herbicides.

To control an existing stand of purple nutsedge in an actively growing warm-season turf grass, at least

two applications of most herbicides will usually be required.

Four to six weeks after making an initial herbicide application, new purple nutsedge shoots will emerge.

The plants arise from dormant tubers that were not connected to purple nutsedge shoots when the initial

herbicide application was made.

This new stand of purple nutsedge must be treated to prevent new tubers from repopulating the soil. If

possible, wait 2–3 months between herbicide applications to allow the entire population of purple

nutsedge shoots to emerge before reapplication. In any herbicide control program for purple nutsedge, it

is important not to allow the weed to grow untreated for longer than 3 months.

Most purple nutsedge shoots die naturally after 3 months, eliminating the living connection to the tubers.

Thus, many tubers will escape herbicide treatment and serve as sources of re-infestation.

This reserve can last for 2 years or longer. Thus, in order to effectively reduce the purple nutsedge tuber

population in the soil, herbicides must be reapplied about every 3 months for about 2 years. Some

herbicides have use limitations, and application directions on the label must be followed.

Biological Control: The taxonomic isolation of the species from crop plants of importance

makes it an ideal target for biocontrol (Ellison & Barreto 2004). Most of the biological control work

undertaken so far has involved insect natural enemies with little success (Julien and Griffiths

1998, in Ellison & Barreto 2004). The mycoherbicide Dactylaria higginsii is a biological control

fungus against purple nutsedge; repeated applications of D. higginsii provided 90% purple

nutsedge control (Kadir et al. 2000, in Yandoc et al. 2006).

Use of Allelopathic Plants: The use of allelopathic plants for weed management is an important

tool in organic production systems and is gaining importance in the absence of synthetic

fumigants. Plants belonging to the Brassicaceae family are known to exhibit allelopathic weed

suppression (Boydston & Hang 1995, Krishnan et al. 1997, Vaughn & Boydston 1997, in

Bangarwa et al. 2008). Turnip is a glucosinolate-producing Brassicaceae that has been used for

weed suppression in bell pepper (Norsworthy et al. 2007).

Integrated Management:

Methyl bromide has been a critical component nutsedge management . However, the use of

methyl bromide as a pre-plant pest management tool was abolished in 2005 (Webster 2005).

This increases the complexity of pest management. Future pest management systems will need

to incorporate a combination of tactics to manage nutsedges in crop production .

Other cultural control methods

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Biocontrol:

None as general . (According to recent data, mango leaves could be used as a safety tool to

suppress purple nutsedge growth although the commercial herbicide could kill the weeds faster

than the mango leaves).

Mechanical:

Cutting often stimulates the plant to produce tubers and nutlets from new rhizomes.

Mechanical methods to defoliate the plant must be applied repeatedly to deplete food reserves in

the nutlets and prevent storage of new food.

Fire: Likely to be ineffective because of the extensive root system.

Herbicides:

Some groups of herbicides have been effective in managing purple nutsedge.

Up to 3–5 applications/season over 3–4 years may be required to gain control. A single application

may only stimulate new growth from the tubers .

Consult the most recent edition of UAE Ministry of Water & Environment , & agriculture and related

sectors.

Before applying herbicides, read the label for full use and precautionary instructions.

Cultural/Preventive: Learn more to identify this weed. Control new infestations immediately.

Management information- General information is summarized below.

Timeframe

The growth of nut grass and its spread via multiplying tubers and sprawling roots and

occasional seeds is greatly reduced when soil is well-drained and turf grass is healthy

and dense.

Expect multiple applications of selective herbicides onto nut grass across the growing

season for them to be most effective (Always follow product label directions for

dosages, safe mixing/handling and proper timing of applications) .

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