CYPERUS ROTUNDUS (PURPLE NUTSEDGE) IMPACTS INFORMATION CONTENTS 1 INTRODUCTION……………………………………………………………

Pterois volitans (Indo-Pacific Red Lionfish) Management Information

Cyperus rotundus (Purple Nutsedge) Impacts Information

Contents

Introduction…………………………………………………………… ……... Page 1
Agricultural…………………………………………………………………… Page 1
Competition…………………………………………………………………… Page 2
Inhibits the Growth of Other Species……………………………………….. Page 2
Human Nuisance……………………………………………………………… Page 2
References……………………………………………………………………... Page 2

1.0 Introduction

Based on distribution (92 countries) and agricultural impacts (interference with over 50 crops) purple nutsedge (Cyperus rotundus) is the world’s worst weed (Holm et al. 1977, in Bangarwa et al. 2008). Weeds reduce crop yield by competing for resources, exerting allelopathic effects on crops and providing an alternative host for insects and pathogens (Singh Pandey & Singh 2009). The ability of purple nutsedge to reproduce prolifically by asexual means, its complex network of underground structures (tubers, basal bulbs, roots and rhizomes) and its adaptation to high temperatures, solar radiation and humidity, have turned it into a serious agricultural weed in tropical, subtropical and arid regions (Bendixen & Nandihalli 1987, Wills 1987, in Santos et al. 1998; Warren & Coble 1999; Travlos et al. 2009).

2.0 Agricultural

In the United States purple nutsedge is the worst weed of cucurbit and fruiting vegetable crops in the southern states (Webster 2006, Webster and MacDonald 2001, in Webster et al. 2008). Purple nutsedge is a serious weed in rice, sugarcane, cotton, maize and vegetable crops (Bendixen & Nandihalli 1987). It is an important weed in peanut, sorghum and soybean crops (Bendixen & Nandihalli 1987); and in Florida and other tropical and subtropical regions, it is the most troublesome weed in peppers (Capsicum spp.) grown in soils without methyl bromide fumigation (Morales-Payan et al. 2004).

Purple nutsedge infestation causes significant reduction in production of vegetable and grain crops, including tomato (44% to 53% reduction), garlic (89%), okra (62%), cabbage (35%), lettuce (54%), beans (81%), bell pepper (32% to 73%), carrot (39 to 50%), cucumber (43%), radish (70%) and rice (38% to 43%) (Okafor & De Datta 1974 1976, in Morales-Payan et al. 1997; Keeley 1987, Morales-Payan et al. 1998, Santos et al. 1996, William & Warren 1975, in Yandoc et al. 2006). Increased densities of nutsedge are correlated with decreased crop yield. For example, in a study by Santos and colleagues (1998) a density of 50 nutsedge plants/m² reduced radish yields by 15% and a density of 100 plants/m² yield reduced radish yields by 39%. Methyl bromide is being discontinued or phased out in various countries because of environmental concerns and selective herbicides for purple nutsedge are not known to be available. Purple nutsedge is significantly limiting the production of tomato and pepper (Morales-Payan et al. 1997).

3.0 Competition

Purple nutsedge is highly competitive especially under high soil nitrogen conditions (Morales-Payan et al. 1998, Santos et al. 1998, in Iqbal Cheema & An 2008). In many of the crops mentioned above, as nitrogen rates increase, for example through fertilisation, marketable yield losses increase (Santos et al. 1998).

4.0 Inhibits the Growth of Other Species

Purple nutsedge suppresses the growth of adjacent plants (in this case primarily crop plants) (Rice 1984, in Quayyum et al. 2000). This is known as allelopathy. Nutsedge tubers contain allelochemicals including polyphenols, sesquiterpenes, flavonol glycoside, saponin, p-hydroxybenzoic acid, p-coumaric acid, o-coumaric acid, caffeic acid and ferulic acid (Komai & Ueki 1975, Komai et al. 1977, Singh & Singh 1980a 1980b, Leela 1995, in Singh Pandey & Singh 2009).

Tuber extracts of Cyperus reduce seed germination and growth of a number of crop species including rice, corn, cucumber, tomato, sorghum and onion (Singh 1968, Meissner et al. 1979, in Quayyum et al. 2000). Nutsedge-infested soil, infested soil extracts and soil incorporated tubers reduce seed germination of barley, mustard and cotton. They also reduce seedling growth of barley, sorghum, soybean, cotton, cucumber and tomato (Friedman & Horowitz 1971, Horowitz & Friedman 1971, in Singh Pandey & Singh 2009). Purple nutsedge inhibits germination of tomato, onion and cabbage seeds (Kawisi et al. 1998, in Singh Pandey & Singh 2009) and germination, seedling growth and dry weight of okra, pearlmillet, cowpea, sesamum and cucumber (Ameena and George 2002, Jeyasriniwas et al. 2006, in Singh Pandey & Singh 2009).

Allelopathic effects of C. rotundus on banana ‘Grande Naine’ were studied by Singh Pandey and Singh (2009). In vitro Cyperus extract (0.2% and 0.6%) decreased shoot multiplication and shoot length. Cyperus extract (1% and 2%) completely inhibited shoot multiplication but induced rooting. Ex vitro the extracts of 1% and 2% decreased shoot and root length, number of leaves and new roots, fresh weight and total chlorophyll and protein. Decreased photosynthesis occurred.

Sharma and Gupta (2007) found that methanolic tuber extract of purple nutsedge strongly inhibited activity of AChE from electric eel, wheat and tomato; it also inhibited seed germination and growth in wheat and tomato. The authors propose that the inhibitor of AChE in purple nutsedge acts as a chemical agent against herbivorous animals and competing plants.

5.0 Human nuisance

Purple nutsedge is a problematic weed in warm-season turfgrass and is listed among the 10 most common and difficult to control turfgrass weeds in Alabama, Florida, Georgia, Kentucky, Louisiana and Texas in the United States (Webster 2004, in Brecke Stephenson & Unruh 2005).

6.0 References

For references please see the GISD Species Profile for Cyperus rotundus (References Section).

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