Picloram is the most effective, and 2 lb/acre applied in the spring and again in fall will provide 85-90% control for several years.
A less expensive and also very effective method is to mix picloram at .25 lb/acre with 2,4-D at 1 lb/acre.
Euphorbia esula is presently a major economic concern in the northwestern and north-central states of the United States and in the adjacent prairie regions of the provinces of Canada.
Seed development and maturation continue for 4-6 weeks after the appearance of the last flowers with seed dispersal occurring into early August.
The plant usually ceases to grow during the hottest and driest weeks of July and August.
Continuous surveillance and reapplication of the herbicide as shoot control decreases must continue for at least ten years, and probably a good deal longer.
For example, management at Devil's Tower National Monument has been spraying on an annual basis for about 20 years and has significantly reduced but not eradicated spurge populations.
It is replaced by an adventitious shoot that will mature into the flowering shoot.
Infloresences form on the main axis from May to the end of July with flowering and seed development again occurring for a short time in the fall, usually from axillary branches.As the growing season progresses some seedlings will appear to dry up and die but their underground parts will persist and produce adventitious buds especially near the hypocotylar end of the shoot (Raju 1975).The main seedling shoot usually does not survive and flower because of the rapid development of adventitious organs.Control of spurge in wooded or riparian zones can be extremely difficult since picloram is not labelled for use in these areas.Glyphosate and 2,4-D are commonly employed under trees with mixed results.It can completely overtake large areas of land and displace native vegetation.