Glyphosate-resistant Horseweed (Conyza canadensis) Control Using Glyphosate-, Paraquat-, and Glufosinate-Based Herbicide Programs

• Published in: Weed technology Vol. 22; no. 1; pp. 16 - 21
• Main Authors: Eubank, Thomas W, Poston, Daniel H, Nandula, Vijay K, Koger, Clifford H, Shaw, David R, Reynolds, Daniel B
• Format: Journal Article
• Language: English
• Published: 810 East 10th St., Lawrence, KS 66044-7050 Weed Science Society of America 01-01-2008
• Subjects: 2,4-D; Burndown; Conyza canadensis; Crop protection; crop yield; Depopulation; dicamba; field experimentation; glufosinate; Glycine max; glyphosate; glyphosate resistance; herbicide efficacy; herbicide mixtures; herbicide resistance; herbicide-resistant weeds; Herbicides; No tillage; paraquat; pesticide mixtures; Plant density; Plants; preemergent weed control; Relative humidity; Soil water; Soybeans; transgenic plants; Weed control; weed resistance; weeds; yield reduction; Mississippi
• ISSN: 0890-037X; 1550-2740
• DOI: 10.1614/WT-07-038.1

Field studies were conducted in 2005 and 2006 to determine the most effective chemical options within three individual herbicide-based burndown programs, glyphosate, paraquat and glufosinate, for controlling glyphosate-resistant horseweed in Mississippi. Burndown treatments were applied April 5, 2005 and March 15, 2006 to horseweed plants 15 to 30 cm in height. Glyphosate at 0.86 kg ae/ha alone provided 60 to 65% horseweed control 4 wk after treatment (WAT). Control 4 WAT ranged from 73 to 74% when the glyphosate rate was increased to 1.25 kg/ha. Glyphosate at 0.86 kg/ha applied in combination with 2,4-D at 0.84 kg ae/ha or dicamba at 0.28 ae/ha maximized control of horseweed (≥ 90%) 4 WAT and soybean yield. Horseweed control 4 WAT with paraquat alone at 0.84 kg ai/ha ranged from 55 to 63% and control did not improve by increasing the rate to 0.98 kg/ha. Addition of 2,4-D or dicamba to paraquat maximized horseweed control both years (78 to 89%), whereas soybean yield was maximized with addition of dicamba or metribuzin at 0.42 kg ai/ha. Glufosinate applied alone at 0.47 kg ai/ha resulted in at least 88% control of horseweed and maximized soybean yield. Results indicate that effective management of glyphosate-resistant horseweed can be obtained in glyphosate-resistant soybean in glyphosate-, paraquat-, and glufosinate-based preplant weed control programs. Nomenclature: Carfentrazone, chlorimuron, 2,4-D, dicamba, flumioxazin, glufosinate, glyphosate, linuron, metribuzin, oxyfluorfen, paraquat, thifensulfuron, tribenuron, horseweed, Conyza canadensis (L.) Cronq. ERICA, soybean, Glycine max. (L.) Merr. DK 4763RR, AG 4801RR