Purple Nutsedge (Cyperus rotundus) Response to Postemergence Herbicides Varies with Mode of Action and Plant Growth Stage

Authors: Varanasi, Vijaya; BARARPOUR, TAGHI - Mississippi State University; Mubvumba, Partson; Fletcher, Reginald; Reddy, Krishna

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2025
Publication Date: 8/18/2025
Citation: Varanasi, V.K., Bararpour, T., Mubvumba, P., Fletcher, R.S., Reddy, K.N. 2025. Purple Nutsedge (Cyperus rotundus) Response to Postemergence Herbicides Varies with Mode of Action and Plant Growth Stage. Weed Technology. 39(e81), 1–7. https://doi.org/10.1017/wet.2025.10029.
DOI: https://doi.org/10.1017/wet.2025.10029

Interpretive Summary: Purple nutsedge is a competitive and persistent weed in various crops in the state of Mississippi and Southeastern United States. The presence of purple nutsedge can cause up to 58% in yield reductions in cotton and soybean crops. Therefore, there is a need to develop effective herbicide programs that effectively control purple nutsedge and protect crop yields. Research was conducted at USDA-ARS, Stoneville, MS location in 2024 to evaluate the response of purple nutsedge at two different plant heights, 10 to 15 and 15 to 20 cm, to various herbicides currently in use in Mississippi. Herbicides tested were glyphosate, liberty, basagran, permit, and envoke. Glyphosate was the most effective herbicide for purple nutsedge control (> 90%), followed by permit (70-90%) at both plant heights. The number of newly emerged shoots was highest for liberty and basagran, especially when sprayed at 15-20 cm compared to 10-15 cm height. The research showed that both herbicide type and application timing at the recommended plant height are important for effective purple nutsedge control in crops.

Technical Abstract: Purple nutsedge (Cyperus rotundus L.) is a highly competitive and persistent perennial weed in the agronomic and horticultural cropping systems of the Southeastern United States. Its management is a challenge during the growing season due to purple nutsedges’ ability to propagate vegetatively through underground rhizomes and tubers. Therefore, there is a need to develop effective herbicide programs that could check the spread of purple nutsedge and protect crop yields. Greenhouse experiments were conducted in 2024 to evaluate the response of purple nutsedge at two different growth stages; 10 to 15 and 15 to 20 cm heights, to postemergence herbicides currently labeled for use in Mississippi cropping systems. Herbicides tested were glyphosate (1261 g ai ha-1), glufosinate (672 g ai ha-1), bentazon (1681 g ai ha-1), halosufuron (69.5 g ai ha-1), and trifloxysulfuron (6.9 g ai ha-1), respectively. Herbicides were sprayed using an automated research track spray chamber. Glyphosate was the most effective herbicide for purple nutsedge control (> 90%), followed by halosulfuron (70-90%) at both plant heights 28 days after treatments. New shoot emergence was highest for glufosinate and bentazon and zero for glyphosate and halosulfuron treatments. More new shoots were observed when glufosinate and bentazon were applied at 15-20 cm compared to 10-15 cm in height. Shoot regrowth at 21 days after cutting the above ground shoots indicated similar trends. Shoot and root biomass reduction was highest (> 90%) with glyphosate, halosulfuron, and trifloxysulfuron treatments, with less biomass reduction (< 50%) after glufosinate and bentazon applications. Overall, herbicide efficacy on purple nutsedge was higher when sprayed at the recommended 10-15 cm stage rather than at the taller 15-20 cm growth stages. The results indicate that both herbicide mode of action and application timing at the recommended growth stage are important for purple nutsedge management in cropping systems.