Imazathapyr, with the trade name Pursuit, is a selective systemic herbicide with a residual effect from the imidazolinone group. The best time to use this herbicide on alfalfa is at the beginning of weed growth and as a post-emergence herbicide. Adding ammonium sulfate or phrigite to the solution prepared for spraying increases the absorption property by weeds. Its use should be avoided in the last year of alfalfa cultivation. The higher the organic matter in the soil, the higher the absorption by the soil, so the availability of the herbicide through the roots decreases. Imazathapyr causes the death of weeds by stopping the production cycle of amino acids (valine, lysine and isoleucine) by reducing their levels. Imazathapyr is absorbed through the roots and leaves and flows into the xylem and phloem of the plant.