After 2 years, imazethapyr residues have no effect on crops in Imperial Valley

A study was conducted in the Imperial Valley to determine the effect of soil residues on subsequent rotational crops after the herbicide imazethapyr is applied to alfalfa. Imazethapyr's label recommends a plantback interval of up to 40 months for sugarbeet and most rotational crops grown in this region. Wheat, lettuce, cotton, tomato and cantaloupe yields were not reduced by imazethapyr. Broccoli, carrot, sugarbeet and sudangrass yields were lower in imazethapyr plots when these crops were sown 11 months after treatment. But after 2 years, soil residues at the maximum-allowed application rate had no effect on any of the rotational crops we studied. Therefore, imazethapyr's plantback recommendations may be too conservative for crops grown in rotation with alfalfa in the Imperial Valley.