NOTES: 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.
See section on Soil Fumigation Outdoors. Proper use of Vapam can provide control of most weed species.
Stale Seedbed
- glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
- pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.
Preemergent Herbicides (before weeds germinate)
- dimethenamid (Outlook): PHI 30d, REI 12h, Group 15. Apply 8-21 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 21 oz/A per year. Use the lower rate on sandy soils and the higher rate on silt and clay soils. Apply to garlic that has at least 2 fully expanded true leaves or significant crop damage may occur. If applying to transplants, do not apply until transplants are in the group and have had several days to recover.
- pendimethalin (Prowl H2O): PHI 30d, REI 24h, Group 3. Apply up to 2 pt/A per application, up to 2 applications allowed per year, a minimum of 30 days apart. Do not exceed 4 pts/A per year. Apply to the soil surface after planting but before crop emergence, or after crop emergence when leeks are at the 2- to 3-leaf stage, or at both timings. Emerged weeds will not be controlled.
Postemergent Herbicides (after weeds germinate)
- carfentrazone-ethyl (Aim EC): REI 12h, Group 14. Apply 0.5-2 oz/A per application, multiple applications allowed per year. Do not exceed 6.1 oz/A per season. Can be applied as a preplant burndown no later than 30 days before planting by seed. Can also be applied to row middles of emerged crops with hooded sprayers to control emerged weeds. 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 14d, REI 1d, Group 1. Apply 6-32 oz/A per application, up to 4 applications per year (or 2 if using 32 oz/A), 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.
- 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. 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.
- pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. Apply a 3-10% solution (3-10 gallons per 100 gallons of spray). Rate based on target weed species. Apply in 75-200 gal/A of spray or with a spot sprayer until foliage is wet but not to the point of runoff. Repeat applications as necessary. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth taking care to avoid contact with foliage and green tissue of crops, or after harvest.
- sethoxydim (Poast): PHI 30d, REI 12h, Group 1. Apply up to 1.5 pt/A per application, multiple applications allowed per year, a minimum of 14 days apart. Do not exceed 3 pts/A 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.