Legume seedlings are relatively slow growing, whereas weeds often have a rapid initial growth period. Thus, in new seedlings, weeds compete strongly with the legume seedlings for light, moisture, and nutrients. Severe reduction or loss of stands may result. Several preplant incorporated treatments are available that offer good annual grass control and some broadleaf weed control at establishment. In addition, postemergence treatments available for use on new stands give good broadleaf weed control. Once a stand is established, weeds may continue to reduce yields and impair quality of the forage. Both residual-type herbicides and postemergence herbicides are available for use in established forage stands. Most are recommended for fall or spring dormant application. Pick the treatment that best suits the specific weed infestation, and carefully follow label directions in terms of timing and rates of application.
Spray volumes for forage areas should be 20 to 30 gallons per acre. Lower volumes will also work but increase the risk of spray drift.
The following table illustrates the susceptibility of common alfalfa weeds to recommended herbicides. Herbicide application timings include establishment, seedling stands, fall or spring dormant, and postcutting. Note that four treatments may be used either in seedling stands or as fall or spring treatments in established stands.
