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. Carrots 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

linuron (Lorox DF): PHI 14d, REI 24h, Group 7. Parsnips only. Make a single application of 1.5 to 3 lbs/A after planting but prior to crop emergence. Seed should be planted at least 1/2 inch deep.

pendimethalin (Prowl H2O): PHI 60d, REI 24h, Group 3. Carrots only. Apply 2pt/A to the soil surface within 2 days of seeding. Do not apply over the top of emerged carrots.

s-metolachlor (Dual Magnum): REI 12h, Group 15. MASSACHUSETTS, MAINE, and NEW HAMPSHIRE ONLY. Carrots only. This is a restricted label available only to those growers who apply 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.

trifluaralin (Treflan 4E): REI 12h, Group 3. Carrots only. Apply 1 to 2 pts/A as a preplant soil incorporated treatment. 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 Pre- and Postemergence to Weeds

prometryn (Caparol 4L):  PHI 30d, REI 12h, Group 5. Carrots only. Primarily controls annual broadleaf weeds. Annual grasses may only be suppressed. Can be applied preemergence and/or postemergence over the top to carrot. Up to three applications at the rate of 2 - 4 pt/A per application are permitted.  Do not exceed 8 pt/A per crop cycle. Do not exceed one preemergence application (up to 4 pt/A) plus two postemergence applications each at up to 2 pt/A or one postemergence application at up to 4 pt/A.  Use lower rate on coarse-textured sandy soils and the higher rate on fine-textured soils. 

For preemergence use, follow with overhead irrigation if rainfall does not occur to activate.

For postemergence use, apply after the crop is at the six-leaf stage. Include nonionic surfactant (0.5% v:v, 2 qt per 100 gallons of spray) or crop oil concentrate (1% v:v, 1 gallon per 100 gallons of spray). Do not apply when temperatures exceed 85°F.

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, 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.

fluazifop (Fusilade DX): PHI 45d, REI 12h, Group 1.  Carrots only.  For grass weed control only. Apply 6 to 16 oz/A.  See label to select rate based on grasses targeted for control. Allow for minimum 14-days between applications, and not to exceed 48 oz/A per year.  Apply to actively growing grasses (see product label for susceptible stage). Add either crop oil concentrate (0.5-1%, 0.5-1 gallon per 100 gallons of spray) or nonionic surfactant (0.25-0.5%, 1-2 qt per 100 gal of spray).

linuraon (Lorox DF): PHI 14d, REI 24h, Group 7.  Carrots only.  Carrot varieties can vary in their tolerance to Lorox.  Apply 1.5 to 3 lb/A after carrots are at least 3".  Multiple applications are permitted, not to exceed a total of 4 lb/A per season. Apply before annual grasses exceed 2" tall and before broadleaf weeds exceed 6" tall. Do not exceed 40 psi spray nozzle pressure as crop injury may result. Do not apply when the temperature exceeds 85° F as crop injury may result. Do not apply Lorox as a tank mix with surfactant, nitrogen solution or other pesticides.

metribuzin (Metribuzin 75): PHI 60d, REI 12h, Group 5.  Carrots only. Apply 0.3 lb/A when carrots have 5 to 6 true leaves and weeds are less than 1" tall and 1" in canopy diameter. A second application can be made 3 weeks after the first. Do not apply within 3 days of cool or wet weather or within 3 days of other sprays. Fair on grasses.

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, REI 12h, Group 1.  Carrots only. Controls grass weeds only.  Apply to actively growing grasses (see product label for susceptible stage).  Maximum 2.5 pt/A per application, minimum 14-days between applications.  Do not exceed 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.