Leafy Spurge Control with Herbicides in North Dakota: 20-Year Summary

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Abstract
Leafy spurge (Euphorbia esula L.) control by herbicides can vary from year to year due to changing environmental conditions. Data from leafy spurge control experimental and demonstrational plots with 2,4-D[(2,4-dichlorophenoxy)acetic acid], dicamba (3,6-dichloro-o-anisic acid), picloram (4-amino-3,5,6-trichloropicolinic acid) and glyphosate [N-(phosphonomethyl)glycine] were combined from 1963 through 1982. The amine and ester formulations of 2,4-D provided similar leafy spurge control. 2,4-D at rates up to 4.5 kg/ha provided less than 40% control after 1 year, and annual (spring or fall) or biannual (spring and fall) 2,4-D applications did not increase leafy spurge control. Dicamba was most effective as a liquid formulation when spring applied and as a granular formulation when fall applied. Dicamba at 9.0 kg/ha was required for satisfactory leafy spurge control for 1 year. Picloram at 2.2 kg/ha gave over 90% control of leafy spurge for 2 growing seasons regardless of formulation or time of application. Synergistic weed control was observed when 2,4-D at 1.1 kg/ha or less was applied with dicamba or picloram at 0.6 kg/ha or less. These synergistic herbicide combinations are economical on many pasture and rangeland sites infested with leafy spurge. Fall-applied glyphosate at 0.8 kg/ha or more gave good control of established leafy spurge for 1 year in shelterbelts and as a spot treatment.