REDUCING VELVETLEAF (ABUTILON-THEOPHRASTI) AND GIANT FOXTAIL (SETARIA-FABERI) SEED PRODUCTION WITH SIMULATED-ROLLER HERBICIDE APPLICATIONS

The potential of preventing seed production and reducing seed viability of weeds that commonly grow taller than soybeans [Glycine max (L.) Merr. "Williams 82''] was evaluated. Chlorflurenol (2-chloro-9-hydroxy-9H-fluorene-9-carboxylic acid), chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl]benzenesulfonamide}, and glyphosate [N-(phosphonomethyl)glycine] were evaluated against sparse stands of velvetleaf (Abutilon theophrasti Medik. #3 ABUTH) and giant foxtail (Setaria faberi Herrm. # SETFA) growing in soybeans. Simulated-roller applications of all three herbicides significantly reduced seed production and germination of both weeds, although glyphosate was more effective than were the other two. Applications during early flowering of velvetleaf and early heading of giant foxtail reduced seed production more than later applications when some seeds were present. With the early application of glyphosate, 99% prevention of velvetleaf and 96% prevention and giant foxtail seed production were attained. With the early glyphosate application, germination of seeds produced was reduced by 50% in velvetleaf and by 95% in giant foxtail. Soybean yields were not reduced by either glyphosate or chlorflurenol but were drastically reduced by chlorsulfuron.