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ARS Home » Southeast Area » Houma, Louisiana » Sugarcane Research » Research » Publications at this Location » Publication #259750
Title: Effect of glyphosate application timings and methods on glyphosate-resistant cotton

Author
item Viator, Ryan
item JOST, P - Georgia Cooperative Extension Service
item SENSEMEN, S - Texas A&M University
item COTHREN, J - Texas A&M University

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2004
Publication Date: 1/30/2004
Citation: Viator, R.P., Jost, P.H., Sensemen, S.A., Cothren, J.T. 2004. Effect of glyphosate application timings and methods on glyphosate-resistant cotton. Weed Science. 52(1):147-151.

Interpretive Summary: Under certain conditions, application of glyphosate to glyphosate-resistant cotton can lead to fruit shedding and yield reductions. Glyphosate at 1.12 kg ai ha-1 when precisely postdirected at the 8th leaf stage, postdirected with 25% foliage coverage at the 8th or 18th leaf stage, or over the top at the 18th leaf stage reduced yield mainly due to lower mean boll weight. Thus, glyphosate contact with leaves and stems should be avoided when applying glyphosate after the four-leaf stage to prevent possible yield loss.

Technical Abstract: Under certain conditions, application of glyphosate to glyphosate-resistant (GR) cotton can lead to fruit shedding and yield reductions. Field studies were conducted at the Texas Agricultural Experiment Station using GR cotton, cv. ‘DeltaPine 5690RR’, to determine if application method and timing affect cotton fruit retention. Glyphosate at 1.12 kg ai ha-1 was precisely postdirected (PD), postdirected with 25% foliage coverage (PDFC), or applied over the top (OT) at the 8- or 18-leaf stage after an initial topical application of 1.12 kg ha-1 glyphosate at the four-leaf stage. In one of the years of this study, 8 PD, 18 PDFC, and 18 OT reduced yield. In 1999 and 2000, 8 PDFC and 8 OT applications of glyphosate caused yield loss, mainly due to lower mean boll weight. Glyphosate applied topically at the eight-leaf stage also affected the Position 1 boll retention throughout the plant in both years. Glyphosate contact with leaves and stems should be avoided when applying glyphosate after the four-leaf stage to prevent possible yield loss.