Therefore, a combination of herbicides may control a broader range of weed species. Lower doses of two combined herbicides can usually be applied more efficiently than a higher dose of a single herbicide. Lower doses of herbicides reduce damage to the crop and lower the active residues left behind in the crop and soil, ultimately reducing environmental impacts. Lastly, combining herbicides greatly reduces the ability of weeds to develop resistance to treatments. A study performed by Orloff and Cudney, found that combination treatments of 2,4-DB amine plus Pursuit, Sethoxydin, or Pronamide, provided the most complete control of weed species.
Young weeds are far easier to control than well-established weeds.
In fact, late application of post emergent herbicides is the most common reason for herbicide failure. One of the trials conducted at the CSUC farm was a timing trial. The optimal time for herbicide applications is well established. The objective of this timing trial is to provide the local growers with information on weed susceptibility at different growth stages, in the event that the grower failed to apply herbicide at the optimum time. Four post emergent herbicide trials in seedling alfalfa were established in the fall of 1998.