Introduction:
Coco Grass (Cyperus rotundus)
Cyperus rotundus (purple nutsedge) is a weed in over 90 countries and the world’s worst invasive weed based on its distribution and effect on crops. Its complex underground network of tubers, basal bulbs, roots and rhizomes ensure its ability to survive and reproduce during adverse conditions. Further biological features, such as its adaptation to high temperatures, solar radiation and humidity, have turned this weed into a serious problem in subtropical and even arid regions.
Description:
Cyperus rotundus (purple nutsedge) is a smooth, erect and perennial weed with an extensive subterranean tuber system. It usually attains a height of about 30 cm. Purple nutsedge appears grass like, but its stems are triangular in cross-section. It has fibrous roots that branch prolifically, rhizomes, tubers, bulbs, and inflorescences that consist of irregular compound umbels. Its leaves are mostly basal and linear in shape with a prominent mid-rib.
Occurs in:
Agricultural areas, coastland, riparian zones, water courses.
Geographical range:
Native Range: Purple Nutsedge is native to Eurasia.
Known Introduced Range: Purple nutsedge is present in 92 countries.
Distribution Map:
Coco Grass (Cyperus rotundus) Distribution in North America shown in green.
Management:
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).
Coco Grass (Cyperus rotundus) Growing from pavers.
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.
Chemical Control: Glyphosate and paraquat are commonly used nonselective herbicides for controlling weeds in vegetable rows, especially those systems with mulch-covered beds. Glyphosate is translocated through chains of purple nutsedge tubers, which reduces tuber viability and production.
Biological Control: The taxonomic isolation of the species from crop plants of importance makes it an ideal target for biocontrol. Most of the biological control work undertaken so far has involved insect natural enemies with little success. The mycoherbicide Dactylaria higginsii is a biological control fungus against purple nutsedge; repeated applications of D. higginsii provided 90% purple nutsedge control.
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. Turnip is a glucosinolate-producing Brassicaceae that has been used for weed suppression in bell pepper .
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 (scheduled to be) abolished in 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.
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