Morningglory (Ipomoeaspp.) and Large Crabgrass (Digitaria sanguinalis) Control with Glyphosate and 2,4-DB Mixtures in Glyphosate-Resistant Soybean (Glycine max)1

Abstract

Abstract: Glyphosate effectively controls most weeds in glyphosate-resistant soybean. However, it is sometimes only marginally effective on Ipomoea spp. A field experiment was conducted at five locations in North Carolina to determine the effects of mixing 2,4-DB with glyphosate on Ipomoea spp. control and on soybean injury and yield. The isopropylamine salt of glyphosate at 560, 840, and 1,120 g ai/ha controlled mixtures of tall morningglory, entireleaf morningglory, and red morningglory at least 96% at two locations. Mixing the dimethylamine salt of 2,4-DB at 35 g ae/ha with glyphosate did not increase control but reduced soybean yield 6%. At two other locations, 2,4-DB increased control of tall morningglory and a mixture of entireleaf morningglory and ivyleaf morningglory 13 to 22% when mixed with glyphosate at 560 g/ha, but not when mixed with glyphosate at 840 or 1,120 g/ha. Soybean yield was reduced 31% at one location and was unaffected at the other. At the fifth location, 2,4-DB increased control ...