Weed Control

Critical Period and General Information: For optimum growth and highest pepper yields, aim to keep production areas weed-free for the first 8 to 10 weeks after transplanting until pepper plants are large enough to be competitive with weeds.

Hairy galinsoga can be an issue in pepper production fields because this weed is not controlled by most herbicides registered for use in pepper and because it resists cultivation. Stale seed beds can help by encouraging and then killing off the initial flush of germinating galinsoga seeds.  If galinsoga is an issue, rotate to crops where the use of herbicides that are known to control galinsoga are permitted (such as beets where Stinger can be applied, or sweet corn where atrazine herbicides are registered for use) to help reduce the number of short-lived galinsoga seeds in the soil.  

Eliminate small patches of Solanaceous weeds, such as jimsonweed and horsenettle, prior to transplanting peppers because they are in the same plant family as pepper and can serve as alternate hosts and sources for disease and insect pests.

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 in the Weed Management section.

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

paraquat (Gramoxone SL 2.0*): restricted use. REI 12h, Group 22. 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

clomazone (Command 3ME): REI 12h, Group 13.  Used for suppression or control of annual grass and broadleaf weeds when applied before weed emergence, including common lambsquarters, velvetleaf, and jimsonweed. Apply 0.67 to 2.67 pt/A to the soil surface prior to transplanting prior to seeding or transplanting, or after seeding but prior to crop emergence. Place seed or roots of the transplants below the chemical barrier when planting. Use the lower rate on coarse-textured soil and the higher rate on fine-textured soil. 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. Do not use on banana peppers.

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

napropamide (Devrinol 2-XT): REI 12h, Group 15. Can be broadcast applied, including use under plastic mulch, or be applied to row middles only. Apply up to 2 to 4 qt/A to a weed-free surface as preplant incorporated or as a surface spray after planting. Must be shallow incorporated or incorporated thoroughly with irrigation if adequate rainfall does not occur within 24 hours of application.

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.

pendimethalin (Prowl H2O): REI 24h, PHI 70d, Group 3. Apply 1 to 3 pt/A, either as preplant incorporated or to the soil surface PRIOR to transplanting. If applied to the soil surface, excessive treated soil falling into the transplant hole may delay crop growth. Can be used under plastic mulch. Can also be applied as a post-directed spray on the soil at the base of the plant, beneath plants, and between rows. Avoid direct contact with foliage or stems or injury will occur.  Apply before weed germination. Emerged weeds will not be controlled.

trifluralin (Treflan HFP): REI 12h, Group 3. Transplants only. Incorporate 1 to 2 pt/A before transplanting.  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. Poor weed control in soils that are wet or are subject to prolonged periods of flooding.

Herbicides used Pre- and Postemergence to Weeds

halosulfuron (Sandea): PHI 30d, REI 12h, Group 2. Apply to row middles only.  Apply ½ to 1 oz/A.  Will provide both preemergence and postemergence control of many weed species. Avoid contact of the herbicide and the planted crop. If plastic is used on the planted row, adjust equipment to keep the herbicide off the plastic. Reduce rate and spray volume in proportion to the area actually sprayed. See the label for other precautions and a list of weeds controlled.

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 areas between rows only 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 20d, 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.

paraquat (Gramoxone SL 2.0*): REI 12h, Group 22.  For use between rows after crop establishment. Apply up to 2 pt/A as a directed and shielded spray to emerged weeds between rows only when weeds are succulent and weed growth is less than 6”. Maximum 3 applications per year.  Use precision directed spray application equipment adjusted to prevent spray contact with crop plants. Crop contact by the spray will cause severe injury or death. Do not exceed 30 psi nozzle pressure or spray under conditions which may cause excessive drift.

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 7d, 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 4.5 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.