WEED-CONTROL IN SOYBEAN (GLYCINE-MAX) WITH LACTOFEN PLUS CHLORIMURON

Field experiments were conducted over a 3-yr period at three locations to evaluate lactofen at rates of 110 to 220 g ai ha-1 applied POST in combination with chlorimuron at 9 g ae ha-1 for weed control in soybe an. At St. Joseph in 1989 and Baton Rouge in 1990, lactofen at 110, 15 0, and 170 g ha-1 in combination with chlorimuron controlled prickly s ida (3 to 5 cm) and entireleaf and pitted morningglory (5 to 13 cm) co mparable with the full rate of lactofen at 220 g ha-1 plus chlorimuron and the standard treatment of acifluorfen at 280 g ae ha-1 plus benta zon at 560 g ae ha-1. Entireleaf morningglory and sicklepod control at Alexandria with lactofen at 110 to 170 g ha-1 plus chlorimuron was co mparable with that from the full rate of lactofen plus chlorimuron and better than with acifluorfen plus bentazon. Weed control was reduced when soil moisture was deficient at treatment time or when prickly sid a height was more than 5 cm and entireleaf morningglory, pitted mornin gglory, and sicklepod more than 15 cm. In related studies at St. Josep h, a reduced rate of lactofen (170 g ha-1) in combination with chlorim uron controlled prickly sida 98%, pitted morningglory 93%, and entirel eaf morningglory 90% in 1988, which was comparable with the control fr om the full rate of lactofen plus chlorimuron and with acifluorfen plu s bentazon.