Reduced herbicide rates often can be used at that time. Biological control agents are available from Colorado Department of Agriculture. Their habitat requirements vary. The copper spurge flea beetle does well in coarse soils with high-water tables in open and shaded condition. The black spurge flea beetle prefers moist clay soils.
Adults feed on leaves but larvae bore into leafy spurge roots, causing the majority of plant damage.
The key to successful management is to prevent seed formation. Musk thistle occurs in pastures in direct proportion to moisture and sunlight. The weed grows more in pastures in poor condition than those in good condition. Reseeding may be a necessary final management step to prevent reinfestation by musk thistle. Cut off the weed below the soil line before the bud stage or treat the weed in spring or fall with herbicides.