Outdoor studies were conducted to determine the extent of leafy spurge biomass reduction resulting from broadcast application of 2,4-D (2,244 g ae ha–¹) with and without wiper-applied glyphosate. Glyphosate (575 g ae L^–1) was applied at 0%, 33%, 50%, and 75% diluted concentrate with a wiper 24 h after 2,4-D was broadcast-applied. Injury estimates and shoot biomass did not differ between plants treated with 2,4-D only or when glyphosate was wiper-applied 21 d after treatment. Shoot regrowth biomass of plants treated with 2,4-D only was approximately 560% greater than nontreated plants 3 mo after treatment. Plants treated with wiper-applied glyphosate exhibited shoot regrowth biomass of less than 10% compared with nontreated plants 3 mo after treatment. Root biomass of plants treated with 2,4-D only (160% of nontreated plants) exhibited a similar pattern of shoot regrowth biomass. Root biomass of plants treated with wiper-applied glyphosate exhibited approximately 50% reductions compared with nontreated plants. All vegetative metrics were equally reduced with all tested concentrations of glyphosate; therefore, all labeled concentrations should be effective. The results of the experiment indicate that broadcast-applied 2,4-D is more effective at reducing leafy spurge biomass with the addition of wiper-applied glyphosate.

Nomenclature: 2,4-D; glyphosate; leafy spurge; Euphorbia esula L.