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.

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

cycloate (Ro-Neet):  REI 48h, Group 8. Not for use in Vermont, Connecticut or Rhode Island. Apply 1/2 gal/A in 10 to 50 gallons of water per acre. Must be immediately incorporated into the soil to a depth of 2 -3” to prevent loss of the herbicide. Crop should be planted or seeded immediately after application.  Use lower rate during hot weather and/or dry soil conditions. Can be applied preplant incorporated, or at planting. To reduce the risk of crop injury, apply and incorporate 7 to 10 days before planting, then rework soil at planting. Use on sandy mineral soils only, but may cause crop injury on very light sandy soil.  Works by interfering with seed germination and seedling development.  Will not control existing weeds. 

s-metolachlor (Dual Magnum): REI 12h, Group 15. MASSACHUSETTS, MAINE, and NEW HAMPSHIRE 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.

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 14d, 24hr REI, 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 21d, REI 12h, Group 4.  For postemergence control of weeds in the composite and legume families. Apply to spinach in the 2- to 5-leaf stage and weeds are young and actively growing. Common annuals include galinsoga, ragweed, pineappleweed, clover, and vetch. Perennial weeds controlled include Canada thistle, goldenrod species, aster species, and mugwort (wild chrysanthemum). 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. Some leaf curling may be observed on smaller spinach, particularly at higher use rates.  Crop tolerance may be optimized by selecting the lower application rate necessary for weed control, especially where non-uniform emergence has caused variable plant sizes.  Use 0.25 to 0.5 pt/A.  Can use up to two applications per year, but can not exceed 0.5 pt/A per year.  Spray additives are not needed or required by the label and are not recommended. Stinger is a postemergence herbicide with some soil residual activity. Observe replant restrictions on the label or injury may occur from herbicide carryover.

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 15d, REI 12h, Group 1.  Controls grass weeds only.  Apply to actively growing grasses (see product label for susceptible stage).  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.  For beets, maximum 2.5 pt/A per application, minimum 14-days between applications.  Do not exceed 5 pt/A per year. For chard, maximum 1.5 pt/A per application, minimum 14-days between applications.  Do not exceed 3 pt/A per year. 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.