Weed Control : New England Vegetable Management Guide : UMass Amherst

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.

Stale Seedbed

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

carfentrazone (Aim EC): PHI 0d, REI 12h, Group 14.
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)

bensulide (Prefar 4E): REI 12h, Group 0. Apply 5-6 qt/A per application, only 1 application per year. Can be applied before planting or after planting before crop has emerged. Incorporate 1-2” into the soil within 36 hours by shallow cultivation or with water through irrigation or rainfall. Grass control only; should be supplemented with cultivation or another registered herbicide for broadleaf control.
napropamide (Devrinol 2-XT): REI 24h, Group 0. Apply up to 2 qt/A per application, only 1 application allowed per year. Apply in 10-100 gal/A of spray. Can be applied after direct seeding or transplanting. Incorporated 4-8” into the soil with shallow cultivation or water through irrigation or rainfall within 24-72 hours of application.
oxyfluorfen (Goal 2 XL): REI 24h, Group 14. Transplanted broccoli, cabbage, and cauliflower only. Apply 1-2 pt/A per application, only 1 application allowed per year. The soil surface should be free of excessive plant residue before applying. Apply to the final seedbed before transplanting and minimize soil disturbance when transplanting. Rate based on soil texture and organic matter, use lower rates on sandy soils. Temporary crop injury may occur, especially if leaves come into contact with treated soil. Applications made to stressed transplants may lead to crop damage and reduced yields. To decrease the risk of injury plant transplants that are hardened off, older, and grown in containers larger than 1 square inch.
pendimethalin (Prowl H2O): PHI 60d for broccoli, 70d for all others, REI 24h, Group 3. For broccoli, brussels sprouts, cabbage, and cauliflower only. Apply 1-2.1 pt/A per application, only 1 application per year. Apply as a directed spray to the soil beneath plants and between vegetative rows of brassica head and stem vegetables. Apply when crop is at the 2- to 4-leaf stage. For transplants this will be about 1-3 days after transplanting. Do not spray foliage or stems because crop injury will occur. If rainfall or irrigation does not occur, mechanically incorporate to activate the herbicide.
s-metolachlor (Dual Magnum): REI 24h, Group 15. MASSACHUSETTS and NEW HAMPSHIRE only: For broccoli, cabbage, and leafy brassica greens only. MAINE: cabbage only. Make sure the label for your state is available for download before using this product. This is a restricted label available only to growers who apply through the website www.syngenta-us.com/labels/indemnified-label-login and agree to a waiver of liability. Main target weeds for this registration are galinsoga and yellow nutsedge.
sulfentrazone (Aquesta 4F): REI 12h, Group 14. For head and stem and cabbage transplants apply 2.25-12 oz/A per application. Do not exceed 12 oz/A per year. For leafy greens apply 2.25-6.4 oz/A per application. Do not exceed 6.4 oz/A per year. Rate based on soil texture, organic matter and soil pH. Do not use on soils that contain less than 1% organic matter. Product is not to be incorporated any deeper than 2” into the soil. Do not apply to soils that are frozen or have an existing snow cover. For head and stem/leafy greens: Apply to stubble or the soil surface in the fall, or in the spring up to 72 hours before transplanting. For cabbage transplants: Apply to stubble or the soil surface, in the fall, or in the spring from 60 days before planting or transplanting up to 72 hours after transplanting. Application can be broadcast or banded. Preemergence applications up to 72 hours after transplanting should be a banded treatment in the row middles. For all brassicas types, if applying in spring, prior to transplanting, can shallowly incorporate up to 2” into the soil.
trifluralin (Treflan HFP): REI 12h, Group 3. Apply 1-2 pt/A per application, only 1 application per year. Apply before direct seeding or transplanting and incorporate 2-3” into the soil of the final seedbed. Rate depends on soil texture, percent organic matter, rainfall, type of brassica, and whether they're grown for greens. Chinese cabbage and kohlrabi may be especially sensitive, so if applications are made when they are stressed, crop damage and yield reduction may occur.

Postemergent Herbicides (after weeds germinate)

carfentrazone (Aim EC): PHI 0d, 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 7 days before planting by seed or immediately before transplanting. 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 30d for head and stem, 14d for leafy greens, REI 24h, Group 1. Apply 9-16 oz/A per application, up to 4 applications 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.
clomazone (Command 3ME): PHI 45d, REI 12h, Group 13. For all brassicas (direct seeded or transplanted) apply 10.7-21.3 oz/A per application, only 1 application per year. For transplanted cabbage (not direct seeded), apply up to 21.3 fl oz/A per application, only 1 application per year. Apply within 72 hours for all transplanted brassicas, except broccoli and gai lan, which should be treated within 48 hours of transplanting. Apply after direct seeding brassicas, prior to emergence. Use lower rates on coarse soil and higher rates on fine soils. Apply in a minimum of 10 gal/A of spray. Be sure to place roots of transplants below the treated soil when planting. There is limited local data available for Clomazone, so crop tolerance should be verified before treating the entire field.
clopyralid (Stinger): PHI 30d, REI 12h, Group 4. Apply 4-8 oz/A per application, up to 2 applications allowed per year. Do not exceed 8 oz/A per year. Rate based on weed composition. Apply in 10-40 gal/A of spray. Spray additives are not recommended.
glyphosate (Roundup Power Max): PHI 7d, REI 4h, Group 9. Apply 15 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.
paraquat (Gramoxone SL 2.0*): restricted use. REI 12h or 24h, Group 22. For snap and lima beans only. For lima beans, apply 1.3-2.7 pts/A per application. For dry beans, apply 0.8-1.3 pts/A per application. Up to 3 applications allowed per year, a minimum of 7 days apart. Do not exceed 8 pts/A per year for lima beans and 1.3 pts/A per year for dry beans. 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.... The training must be completed a minimum of every three years.
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, 14d for mustard greens, 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.