Improved weed control with broadleaved herbicides in glyphosate-tolerant soybean (Glycine max)

Failure to control certain broadleaved weeds with glyphosate creates the need for other herbicides in glyphosate-tolerant soybean. Field studies were conducted in 2001, 2002 and 2003 to evaluate soybean yield response and control of Solanum sisymbrifolium Lam., Parietaria debilis Nutt., Commelina erecta L. and Sida rhombifolia L. with soil and foliar-applied broadleaved herbicides. Pre-emergence metribuzin, imazaquin and post-emergence imazethapyr and glyphosate controlled S. sisymbrifolium, C. erecta and S. rhombifolia. In 2002 and 2003, in glyphosate-treated plots surviving plants and those emerged along with the crop compete with soybean during 3 or 4 weeks after crop emergence thus reducing crop yield. Soil-applied herbicides may be beneficial for glyphosate-tolerant crops reducing early season competition of weeds, particularly those inherentely more tolerant to glyphosate.