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 (page 107) for information on the use of these herbicides.

glyphosate (Roundup Power Max): REI 12h, Group 9.

paraquat (Gramoxone SL 2.0*): restricted use. REI 12h, Group 22. Broccoli, cabbage, and cauliflower only. Use 2 – 4 pts/A.

pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons).

Herbicides Used Preemergence to Weeds

bensulide (Prefar 4E): REI 12h, Group 8.  Apply 5 to 6 qt/A.  Can be preplant incorporated by shallow cultivation (1-2”) or applied preemergence and incorporated by irrigation within 36 hours of application. Grass control only; should be supplemented with cultivation or another registered herbicide for broadleaf control. See label for rotation restrictions.

clomazone (Command 3ME): PHI 45d, REI 12h, Group 13.  Cabbage only.  For seeded cabbage, apply 0.67 pt/A after seeding to the soil surface. For transplant cabbage, apply 0.67 to 1.3 pt/A to the soil surface prior to transplanting. Use the lower rate on coarse-textured soil and the higher rate on fine-textured soil.  Will control annual grasses and many broadleaf weeds including common lambsquarters, velvetleaf, and jimsonweed.  Some temporary crop injury (partial whitening of leaf or stem tissue) may be visible after crop emergence. Complete recovery will occur from minor early injury without affecting yield or earliness. See label for rotation restrictions.

DCPA (Dacthal 75WP): REI 12h, Group 3.  Apply 6 to 14 lb/A at seeding or transplanting.   Can be sprayed over transplants without injury. Apply at seeding only to leafy brassica greens (kale, mustards, turnips, etc.).  Will not control ragweed, galinsoga or smartweed. Use lower rates on sandy soils.

napropamide (Devrinol 2-XT): REI 12h, Group 15. Apply up to 2 qt/A to a weed-free surface. A higher rate is permitted for use on broccoli in Maine only.  See label for details.  May be applied to direct seeded and transplanted crop as preplant incorporated or as a surface spray after planting. Must be shallow incorporate or incorporated thoroughly with irrigation if adequate rainfall does not occur within 24 hours of application (sufficient water to wet soil to a depth of 2" to 4").

oxyfluorfen (Goal): REI 24h, Group 14.  Pre-transplant application only to broccoli, cabbage, and cauliflower.  Apply 1 to 2 pt/A after completion of soil preparation but prior to transplanting. Do not incorporate. May cause temporary crop injury, and can cause severe crop injury if not applied properly. Read product label carefully before applying. 

pendimethalin (Prowl H2O): PHI 60d for broccoli, PHI 70d for all others, REI 24h, Group 3.  Use as a postemergence-directed spray on the soil beneath plants and between vegetative rows of brassica head and stem vegetables. Apply a single application of up to 2.1 pt/A.  For transplants, apply when crop is at the 2 to 4-leaf stage 1 to 3 days after transplanting.  For direct-seeded crops, apply when crop is at the 2 to 4-leaf stage.  Apply DO NOT spray foliage or stems because crop injury will occur. If rainfall or irrigation does not occur, mechanically incorporate to activate the herbicide. Apply before weed germination. Emerged weeds will not be controlled.

s-metolachlor (Dual Magnum): REI 12h, Group 15.  MASSACHUSETTS AND NEW HAMPSHIRE: Broccoli, cabbage, and leafy brassica greens only.  MAINE: cabbage only.   This is a restricted label available only to growers who register through the website www.farmassist.com and agree to a waiver of liability.  Main target weeds for this registration are galinsoga and yellow nutsedge. All label instructions will be supplied after the application for use is completed. Once on the farm assist web site, click products at top left, then indemnified labels.  Create a username and password, select Dual Magnum, and the crop.

trifluralin (Treflan HFP): REI 12h, Group 3. Incorporate 1 to 1.5 pt/A before seeding crops, or 1 to 2 pt/A before transplanting (broccoli, brussels sprouts, cabbage, and cauliflower).  Can be used before seeding only for greens (collard, kale, mustard and turnip). Select rate based on soil texture, see label for details.  Must be incorporated into the top 2 to 3 inches of the final seedbed within 24 hours of application.  Disc twice after spraying for satisfactory incorporation. See label for info on incorporation recommendations based on different equipment and single pass incorporation.Little or no control of ragweed, galinsoga, mustard or nutsedge.

Herbicides Used Postemergence to Weeds

carfentrazone (Aim EC): REI 12h, Group 14.  Aim is a burndown herbicide and will injure any foliage it comes into contact with. Apply Aim 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 inches tall and rosettes less than 3 inches across. Good coverage is essential for good control.  Apply up to 2 oz/A per application, and do not exceed a total of 6.1 oz/ per season. 

clethodim (Select Max)PHI 30d, PHI 14d for leafy brassica greens, REI 24h, Group 1.  Will control grass weeds only. Apply to actively growing grasses.  See label for rate selection.  Multiple applications permitted of 9 to 16 oz/A per application, minimum 14-days between applications, not to exceed 64 oz/A per year.  Add 0.25% v:v nonionic surfactant (1 qt per 100 gal of spray).  Can also be used as a spot-spray by mixing 1/3-2/3% (0.44 to 0.85 oz per gallon) Select Max and 0.25% v:v nonionic surfactant (0.33 oz per gallon).  Spray to wet, but do not allow runoff of spray solution.

clopyralid (Stinger): PHI 30d, REI 12h, Group 4. Apply 1/4 to ½ pt/A for postemergence control of common ragweed, galinsoga, prickly lettuce, sweet clover, and wild buckwheat and suppression of sowthistle. Stinger is very effective on small seedling annual and emerging perennial weeds less than 2" to 4" tall, but is less effective and takes longer to work when weeds are larger. Spray additives are not needed or required by the label and are not recommended. Stinger is a postemergence herbicide with some soil residual activity. See label for crop rotation restrictions, or injury may occur from herbicide carryover. Make 1 to 2 applications a year, but do not exceed 1/2 pt/A per year.

pelargonic acid (Scythe):  PHI 1d, REI 12h, Group 17. Use a 3 -10% solution (3 to 10 gallons per 100 gallons). Use a 3 to 5% solution for annual weeds, a 5 to 7% solution for biennial and perennial weeds, and 7 to 10% solution for maximum burndown. Delivery rate for boom applications should be 75 to 200 gals of spray solution per acre; complete coverage of weed foliage is essential. Use a DIRECTED/ SHIELDED SPRAY; contact with crop will cause injury. For hand-held equipment, spray to completely wet all weed foliage but not to the point of runoff. Repeat applications as necessary. Tank mixes are allowed with this product. See label for complete details.

sethoxydim (Poast): PHI 30d, PHI 14d for leafy brassica greens, REI 12h, Group 1.  Controls grass weeds only.  Apply to actively growing grasses (see product label for susceptible stage).  Maximum 1.5 pt/A per application, minimum 14-days between applications.  Do not exceed 3 pt/A per year. Use with crop oil concentrate (2.0 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 used as a spot-spray by mixing 1-1.5% (1.3 to 1.9 oz per gallon) Poast and 1% v:v crop oil concentrate (1.3 oz per gallon).  Spray to wet, but do not allow runoff of spray solution.