Leafy spurge (Euphorbia esula) control with glyphosate plus 2,4-D

Abstract

Leafy spurge control with glyphosate [N-(phosphonomethyl)glycine] plus 2,4-D [2,4-dichlorophenoxy)acetic acid] applied annually for 3 years alone or rotated with auxin herbicides was evaluated at 3 locations in North Dakota. Glyphosate applied with 2,4-D averaged 67% leafy spurge control 3 months after treatment which was a 10-fold increase compared to glyphosate alone. Glyphosate plus 2,4-D applied annually for 3 years or rotated with dicamba (3,6-dichloro-2-methexybenzoic acid) or picloram (4-amino-3,5,6-trichloro-2-pyridine carboxylic acid) plus 2,4-D provided 80 to 90% leafy spurge control, which was similar to the standard annual picloram plus 2,4-D treatment but at 30 to 65% less cost. Herbage production was similar regardless of treatment. The absorption and translocation of 14C-2,4-D increased 2- to 3-fold when applied wit glyphosate compared to 14C-2,4-D applied alone. However, both absorption and translocation of 14C-glyphosate was severely reduced when applied with 2,4-D compared to 14C-glyphosate applied alone. The increase in control when glyphosate is applied with 2,4-D may be because sublethal concentrations of glyphosate break root bud dormancy in leafy spurge, thereby increasing the amount of 2,4-D in the root. Glyphosate plus 2,4-D provided good leafy spurge control at less cost than current widely used treatments and should provide a new tool for leafy spurge management.