Summary. Field experiments were conducted to find a herbicide for complete control of nutsedge (Cyperus rotundus L.). We applied seventeen herbicides and some of their combinations as chemical fallow. EPTC and CP‐31675 (6‐tert‐butyl‐2‐chloro‐o‐acetotoluidide) gave good but only temporary control of nutsedge. Dichlobenil at 2·5 or 5 lb/ac gave fair control for 1 year. Rates of 10 or 20 lb/ac of dichlobenil controlled nutsedge completely for 1 year but severely reduced the yield of oats planted 5 months after application. The highest rate completely killed tubers and prevented reinfestation for 1 year. Analyses indicated no residue of dichlobenil or of its metabolite, 2,6‐dichlorobenzoic acid, in vegetative parts and seeds of oats planted 5 months after application of 2.5, 5 or 10 lb/ac of dichlobenil. At equivalent rates the herbicide TH‐073‐H (N‐hydroxymethyl‐2,6‐dichlorothiolbenzamide) gave control of nutsedge similar to that with dichlobenil. The combinations of 8 lb/ac amitrole‐T and 10 lb/ac dichlobenil or TH‐073‐H were just as effective in controlling nutsedge shoots and tubers as dichlobenil or TH‐073‐H applied alone. The mixture of dichlobenil plus CP‐31675, each at 5 lb/ac, gave excellent control of nutsedge and tubers for 1 year. The herbicides terbacil (3‐ter‐Nbutyl‐5‐chloro‐6‐methyluracil) or Du Pont 733 (3‐tert‐butyl‐5‐bromo‐6‐methyluracil) at 10 lb/ac provided almost complete control of nutsedge. Application of terbacil to plants aged 4–6 weeks gave better results than application to mature nutsedge in the fall. La lutte chimique contre le cypirus

Analysis of 3-tert-butyl-5-chloro-6-methyluracil (terbacil) in treated and untreated pairs of purple nutsedge (Cyperus rotundusL.), connected by rhizomes, indicated translocation of the herbicide. The tops and tubers of connected, untreated plants contained approximately 10% as much terbacil as did plants treated directly.

REVIEW OF LITERATURE Nutsedge and Its Control Nutsedge is one of the most persistent weeds in croplands and is very often a serious pest in vegetable crops and in nursery stocks. This weed not only causes reduction in yield through competition for water and minerals in the soil, but also increases the cost of cultivation and lowers crop quality. It is also a problem in lawns, where it spoils the appearance of the turf. Bell et al. (1962) pointed out that nutsedge rhizomes grew through potato tubers, thus increasing the proportion of culls. Nutsedge tubers were also found to pass through bean-shelling equipment, necessitating hand sorting. Although nutsedge is a native of Asia, it is distributed widely in all warm regions and is found in Africa, Australia, and in the warmer parts of Europe. The plant is adaptable to a wide variety of soils and environmental conditions in tropical or subtropical regions (Muenscher, 1955)* In the United States, it is found from Virginia to Florida, Kansas, and Texas. Yellow nutsedge (Cyperus esculentus L.

The existing method for the analysis of 3-tert-butyl-5-chloro-6-methyluracil (terbacil) has been modified so that electron capture gas chromatography may be used for quantitation. The crop extract was applied to a powdered cellulose column, the interferences were eluted with hexane, and the terbacil was subsequently eluted with ethyl acetate. The ethyl acetate fraction may be used for analysis directly.