If can sell or use grassy hay, don't spray. If want to sell weed-free alfalfa hay, you had better spray. In addition this much grassy weeds can damage new alfalfa stands, especially if the weather delays harvesting in spring. If you have had a dock problem in your fields in the past or find any dock seedlings, you probably need to spray 3 pints of Butyrac per acre on your new stand this fall to control seedling dock. The only time dock can be selectively controlled in alfalfa is at establishment while dock is still small.
Next spring is too late .
Also, good control of disturbed old dock plants has been reported with 3 pints of Butyrac applied in fall to seedling alfalfa. A problem that producers have is that weed infestation varies in the field and they can not decide if control will pay. For example, there are often more weeds around field edges. One option would be to just spray a couple of rounds around the edges where the weeds are the thickest. However, my experience is that once a producer does this, he is so satisfied with the results that he wishes he would have sprayed the whole field.