In conventionally managed fields, control weeds with pre-plant and/or pre-emergence herbicides. Apply post-emergence herbicides after the field is cultivated to control broadleaf and grass weeds. Hand-weed or mechanically cultivate as needed.
In organic production systems, apply a preplant irrigation to induce weed emergence. Weeds can then be killed by tillage, flaming, or OMRI-approved organic herbicides (non-selective, contact, limited residual activity). Consult your certifying agent prior to applying organic herbicides.
Users should have a current chemical applicators license, and read and save copies of all labels. Herbicide options are listed in Table 9.3. Herbicide labels change regularly, so always consult a current label to determine (1) if the crop is listed for herbicide use; (2) what precautions are required; and (3) what rates and application methods are allowed. It is a violation of federal law to use any herbicide for purposes other than those specified on the approved label. Always use the recommended amount of product, apply it as stated, and watch reentry intervals (REI) and preharvest intervals (PHI).
Herbicides are applied in the following ways:
- Preplant: incorporated into the soil prior to seeding the crop.
- Preemergence: applied to the soil after planting but before the crop or weeds emerge.
- Postemergence: applied to weeds after both weeds and the crop have emerged.