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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #150507
Title: GLYPHOSATE/MSMA MIXTURES IN GLYPHOSATE-RESISTANT COTTON (GOSSYPIUM HIRSUTUM)

Author
item CULPEPPER, A - UNIVERSITY OF GEORGIA
item Webster, Theodore
item YORK, A - NC STATE UNIVERSITY
item BARENTINE, R - UNIVERSITY OF GEORGIA

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2003
Publication Date: 4/1/2004
Citation: Culpepper, A. S., Webster, T. M., York, A. C., Barentine, R. M., Mullinix, Jr., B. G. 2004. Glyphosate/MSMA mixtures in glyphosate-resistant cotton (Gossypium hirsutum). Journal of Cotton Science. 8:124-129.

Interpretive Summary: Nutsedge species are among the most troublesome weeds infesting cotton in the Southeast U.S. These perennial weeds are propagated by energy-rich tubers, which allow for rapid regrowth following weed management tactics. Also, nutsedge species are tolerant of many of the commonly used herbicides in cotton. Two of these herbicides, glyphosate and MSMA, often only suppress growth of nutsedge species. However, we hypothesized that glyphosate and MSMA applied in combination may be more effective than either herbicide alone. Field and greenhouse experiments were conducted to determine the response of nutsedge and cotton to treatments of MSMA and glyphosate applied in combination and alone at registered use rates. MSMA controlled yellow nutsedge 9 to 20% more than purple nutsedge. In contrast, glyphosate controlled purple nutsedge 9 to 16% more than yellow nutsedge. The addition of glyphosate to < 1.1 kg/ha MSMA increased both yellow nutsedge and purple nutsedge control in a linear manner. There was no benefit of glyphosate mixed MSMA at 2.2 kg/ha for controlling yellow nutsedge. Cotton injury was greater with topically applied glyphosate plus MSMA than with either glyphosate or MSMA alone. Cotton injury increased as the rate of glyphosate or MSMA in the mixture increased. Glyphosate plus MSMA applied topically may be too injurious to cotton, but directed application of glyphosate plus MSMA at 2.2 kg ha-1 to glyphosate-resistant cotton would be an effective method to control both nutsedge species.

Technical Abstract: Nutsedge species (Cyperus sp.) are among the most troublesome weeds infesting cotton (Gossypium hirsutum L.) throughout the Southeast U.S., and they are difficult to manage with topically applied cotton herbicides. Both glyphosate and MSMA can be applied topically to glyphosate-resistant cotton. However, each herbicide applied alone often only suppresses nutsedge. Glyphosate and MSMA applied in combination may be more effective than either herbicide alone. Field and greenhouse experiments were conducted to determine nutsedge and cotton response to MSMA at 0, 0.6, 1.1, and 2.2 kg ai/ha and glyphosate at 0, 0.2, 0.4, 0.6, and 0.8 kg ae/ha arranged factorially. MSMA controlled yellow nutsedge (Cyperus esculentus)9 to 20% more than purple nutsedge (Cyperus rotundus). In contrast, glyphosate controlled purple nutsedge 9 to 16% more than yellow nutsedge. The addition of glyphosate to < 1.1 kg/ha MSMA increased both yellow nutsedge and purple nutsedge control in a linear manner. There was no benefit of glyphosate mixed MSMA at 2.2 kg/ha for controlling yellow nutsedge. Cotton injury was greater with topically applied glyphosate plus MSMA than with either glyphosate or MSMA alone. Cotton injury increased as the rate of glyphosate or MSMA in the mixture increased. Glyphosate plus MSMA applied topically may be too injurious to cotton, but directed application of glyphosate plus MSMA at 2.2 kg ha-1 to glyphosate-resistant cotton would be an effective method to control both nutsedge species.