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Book of Abstracts

11th IFOAM
Scientific Conference
11-15 August 1996
Copenhagen, Denmark

Abstract front page
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Extra Papers

Non-chemical Control of Purple Nutsedge E16

Marambe, B. & Sangakkara, U. R.

Department of Crop Science, Faculty of Agriculture University of Peradeniya, Sri Lanka.

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Purple nutsedge (Cyperus rotundus L.), which is considered the most troublesome weed in the tropics, is continuing to increase it's severity under modern cropping systems. Although chemical techniques have been adopted in the recent past to control this weed, several non-chemical techniques were also reported to be partly successful. The enormous power to regenerate, and the difficulties faced by farmers to kill the large number of tubers have rendered the control of this weed more difficult. The present study was conducted to develop an effective non-chemical method to suppress the growth and development of purple nutsedge. Thus, the effects of partial and complete defoliation treatments imposed at 2 and 4 weeks after emergence (WAE) on weed growth were investigated in field and pot experiments. Repeated-complete defoliation reduced the regrowth ability of the nutsedge tubers when compared to single defoliations and the non-treated control. This treatment reduced the leaf area and leaf dry weight of the weed by 56% and 69% respectively when compared to the control treatment at 8 WAE. The number of new tubers produced was un affected by the defoliation treatments. However, new tubers showed significantly low dry weights when compared to that of the control treatment. Repeated-complete defoliation also reduced the endoamylase (EC activity and the starch content in the mother tubers by 72% and 56%, respectively, at 8 WAE. However, the exoamylase (EC activity of the tubers was unaffected by the defoliation treatments. Single defoliation resulted in poor growth of nutsedge plants during the early stages. However, at 8 WAE, the growth of these plants was similar to that observed in the control plots. The results indicated that complete defoliation at 2 and 4 weeks after emergence would effectively suppress the growth and development of purple nutsedge. This would increase the competitive performance of the crops grown in association with this weed. Reduction of the endoamylase activity could be a major causal factor attributable to the poor performance of purple nutsedge after defoliation.

Marambe, B.; Sangakkara, U. R. & Ratnayake, S. K. (1995): Control of tuber growth of purple nutsedge (Cyperus rotundus L): Effects of drying and depth of burying. Proc. 15th Asian-Pacific Weed Sci. Soc. Vol I (B), p. 562-566.