Weed control in seedling alfalfa

Pre-emergence herbicides offer the advantage of reducing early competition in seedling alfalfa stands. The disadvantages of present pre-emergence herbicides is that they have to be incorporated, which adds extra expense, and they do not control all of the broad-leaved weeds. Benefin shows promise as a pre-emergence herbicide due to good selectivity in alfalfa and full-season grass control. Post-emergence herbicides have the advantage that treatment is not necessary until the problem exists. The dinitros and 2,4-DB (ester) will control weeds if they are small. Bromoxynil (not presently registered for use on alfalfa) kills a larger number of weeds and larger weeds than the other post-emergence herbicides. With the use of post-emergence herbicides, timing the application when the weeds are small and when most of them have emerged is essential. This report results from three years of trials using pre- and post-emergence applications of various herbicides. This information does not constitute a weed control recommendation by the University of California. For current weed control recommendations, local farm advisors should be consulted.