ABSTRACT
Research has shown that topical applications of glyphosate (Roundup Ultra) on Roundup Ready cotton (Gossypium hirsutum L.) after the 4-leaf stage may affect reproductive development. Applications made after the 4-leaf stage are required, by current label restrictions, to be post-directed. Equipment type, adjustment, and speed cause variation in herbicide deposition. Field experiments were conducted in 1997 and 1998 at the Black Belt Branch Experiment Station near Brooksville, MS, the Delta Branch Research Station near Stoneville, MS, and at the Plant Science Research Center near Starkville, MS, to evaluate Roundup Ready cotton tolerance to topical and post-directed applications of glyphosate. In the topical study, treatments consisted of topical applications of 16, 24, and 32 fl oz/A of glyphosate at the 6, 9, and 12 node growth stage following a topical application of 32 fl oz/A of glyphosate at the 3 node stage.
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