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ARS Home » Southeast Area » Houma, Louisiana » Sugarcane Research » Research » Publications at this Location » Publication #259756
Title: Effects of glyphosate application timing and rate on sicklepod (Senna obtusifolia) fecundity

Author
item THOMAS, W - North Carolina State University
item PLINE-SRNIC, W - Syngenta - United Kingdom
item Viator, Ryan
item WILCUT, J - North Carolina State University

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 1/2/2005
Citation: Thomas, W.E., Pline-Srnic, W.A., Viator, R.P., Wilcut, J.W. 2005. Effects of glyphosate application timing and rate on sicklepod (Senna obtusifolia) fecundity. Weed Technology. 19(1):55-61.

Interpretive Summary: Greenhouse experiments were conducted to examine the effect of glyphosate on reproductive development in sicklepod. Glyphosate applied at 112 and 280 g ai/ha had no significant effect on average pod length, 50-seed weight, seed germination, seed viability, and aboveground biomass. The number of pods, seeds, and total seed weight were reduced by 79, 80, and 81%, respectively, with 280 g/ha of glyphosate compared with the nontreated. Thus, glyphosate does affect reproductive development in sicklepod.

Technical Abstract: Greenhouse experiments were conducted to examine the effect of glyphosate on reproductive development in sicklepod. Glyphosate was applied postemergence over the top at 112 and 280 g ai/ha to sicklepod at 4-leaf stage (L), 8-L, 4-L followed by 8-L, and 12-L. A nontreated control was included. Immediately after the 12-L application, number of flowers was recorded for all treatments twice per week for 8 wk. Pollen viability was measured on 1 open flower/plant/sampling time using Alexander stain. The number of pods, pod length, seeds per plant, 50-seed weight, total seed weight, seed germination, seed viability, and dry weight of aboveground biomass were also recorded. No significant differences among the treatments were found for average pod length, 50-seed weight, seed germination, seed viability, and aboveground biomass. The nontreated had 18 flowers counted over 8 wk. Glyphosate applied at 12-L and sequentially at 4-L and 8-L, averaged over glyphosate rates, reduced cumulative flower production after 8 wk by 65 and 54%, respectively, compared with the nontreated. Similarly, glyphosate at 280 g/ha, averaged over treatment timings, reduced flower production by 58% compared with the nontreated. Because the number of flowers produced was limited by glyphosate treatment due to flower abscission, pollen viability measurements could not be analyzed because of large numbers of missing data points. The number of pods, seeds, and total seed weight were reduced by 79, 80, and 81%, respectively, with 280 g/ha of glyphosate compared with the nontreated.