Weed Control

NOTE:  For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases, there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using. 

Stale Seedbed

See Stale Seedbed Technique for information on the use of these herbicides or flaming.

  • glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
  • paraquat (Gramoxone SL 2.0*): restricted use. REI 12h or 24h, Group 22.
  • pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

DCPA (Dacthal 75WP): PHI 25d, REI 12h, Group 3. Turnip only. Apply 6-14 pts/A per application, only 1 application per year. Apply to the soil at seeding. Incorporate with 0.33-0.5” of water through irrigation or rainfall within 3-5 days of application. Use the lower rate on sandy soils and the higher rate on silt and clay soils.

dimethenamid (Outlook): PHI 14d for tops, 40d for roots, REI 12h, Group 15. Apply 7-21 oz/A per application, only 1 application per year. Apply as a broadcast application when rutabaga and turnip have reached the 2-leaf stage but before the 8-leaf stage. Temporary leaf injury may occur.

sulfentrazone (Aquesta 4F): REI 12h, Group 14. Turnip only. Apply 8 oz/A per application, only 1 application per year. Can be applied after turnips have emerged, 40-60 days before harvest in 10-40 gal/A of spray.

trifluralin (Treflan HFP): REI 12h, Group 3. For turnip greens only. Apply 1-1.5 pt/A per application, only 1 application per year. Apply and incorporate before planting. Rate depends on soil texture and percent organic matter.

Postemergent Herbicides (after weeds germinate)

carfentrazone (Aim EC)PHI 0d, REI 12h, Group 14. Apply 0.5-2 oz/A per application. Do not exceed 6.1 oz/A per season. Can be applied to row middles of emerged crops with hooded sprayers to control emerged weeds, including crops grown on mulch or plastic.  Prevent any spray from contacting the crop, or injury will occur.  For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across.

clethodim (Select Max)PHI 30d, REI 24h, Group 1. Apply 9-16 oz/A per application, up to 4 applications allowed per year, a minimum of 14 days apart. Do not exceed 64 oz/A per year.  Apply to actively growing grasses. Add 0.25% v:v nonionic surfactant (1 qt/100 gal of spray).  Can also be applied as a spot-spray by mixing 0.33-0.66% (0.44-0.85 oz/gal) Select Max and 0.25% v:v nonionic surfactant (0.33 oz/gal).  Spray to wet, but do not allow runoff of spray solution.

clopyralid (Stinger)PHI 15d for tops, 30d for roots, REI 12h, Group 4. Turnip only. Apply 5-8 oz/A per application, only 1 application per year. Apply after the crop has emerged. Rate based on weed composition and growth stage. Spray additives are not recommended.

glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9. Apply 10 oz to 3.1 qts/A per application, multiple applications allowed per year. Do not exceed 5 qts/A per year. Rate based on target weed species. Can be applied during fallow intervals, prior to planting or transplanting, at planting, or before crop has emerged. Can also be applied with the wiper method, using a 33% solution by volume. Only 1 wiper application allowed per year, a minimum of 14 days prior to harvest. Could cause injury when applied prior to transplanting or direct-seeding into plastic mulch. Remove residual product from plastic mulch with a 0.5” of water through irrigation or rainfall prior to planting.

paraquat (Gramoxone SL 2.0*): restricted use. REI 12h or 24h, Group 22. Apply 1.3-2.7 pts/A per application, up to 3 applications allowed per year, a minimum of 14 days apart. Do not exceed 8 pts/A per year. Can be applied before, during, or after planting but before emergence. Apply in a minimum of 10 gal/A of spray. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training...(link is external). The training must be completed a minimum of every three years.

pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. Apply in 75-200 gal/A of spray. Can use preplant, or as a directed and shielded spray during crop growth. Avoid contact with foliage or crop damage may occur. Can also be applied as a harvest aid and desicant to remove leaves. Spray to wet, but do not allow runoff of spray solution.

sethoxydim (Poast)PHI 14d, REI 12h, Group 1. Apply 2.5 pt/A per application, only 1 application per year. Apply to actively growing grasses. Use with crop oil concentrate (2 pt/A) or methylated seed oil (1.5 pt/A). Note that crop oil can cause injury under hot and humid conditions. Can also be applied as a spot-spray by mixing 1-1.5% (1.3-1.9 oz/gal) Poast and 1% v:v crop oil concentrate (1.3 oz/gal). Spray to wet, but do not allow runoff of spray solution.