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 in the Weed Management section. In place of herbicides, flaming can also be used.

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

pelargonic acid (Scythe): 1 day PHI, 12 hr REI, Group 27. Use a 3 -10% solution (3 to 10 gallons per 100 gallons).

Herbicides Used Preemergence to Weeds

bensulide (Prefar 4E): 12 hr REI, 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 or application. Grass control only; should be supplemented with cultivation or another registered herbicide for broadleaf control. See label for rotation restrictions.

Herbicides Used Pre- and Postemergence to Weeds

linuron (Lorox DF): 30 day PHI for parsley, 21 day PHI for cilantro, 4 day REI for hand-set irrigation activity and 24 hr REI for all other activities, Group 7.  Can be used preemergence or postemergence.  Best results are obtained when application is made to moist soil (applied after at least ½ inch of rain or irrigation).  Moisture is needed to activate Lorox, and applications should be followed by rainfall or irrigation.

For parsley, do not exceed a total of 3 lb/A per season. 

Parsley Preemergence: For mineral and muck soils, make a single broadcast application of 1 to 3 lb/A after planting, but before the crop emerges. Plant seeds at least ½ inch deep.  Use lower rates on coarse soils and higher rates on heavier soils (soils high in clay and organic matter). Irrigation or rainfall of at least 1/2 inch prior to making application after planting.

Parsley Postemergence (Muck Soils Only): Make a single application of 1 lb/A to control emerged weeds. Apply after parsley has a minimum of 3 true leaves or crop injury may result. Apply when weeds are in the 1 to 3 true leaf stage.

For cilantro, varieties may vary in their susceptibility to injury from Lorox. Determine tolerance to Lorox prior to adoption as a field practice to prevent possible crop injury. Do not exceed a total of 4 lb/A per season. 

Cilantro Preemergence: Make a single broadcast application of 1 to 2 lb/A after planting, but before the crop emerges. Plant seeds at least ½ inch deep.  Use lower rates on coarse soils and higher rates on heavier soils (soils high in clay and organic matter). Additional postemergence applications may be made as long as the total does not exceed the seasonal maximum.

Cilantro Postemergence: Make up to two postemergence applications of 1-2 lb/A to control emerged weeds. Apply after cilantro has a minimum of 3 true leaves or crop injury may result. Apply when weeds are in the 1 to 3 true leaf stage. Early crop injury can occur, however the effect should be transitory, with no yield losses attributable to crop injury. A second application may be made 14 days following the first application but no later than 21 days before harvest.

prometryn (Caparol 4L):  30 day PHI, 12 hr REI, Group 5.  Primarily controls annual broadleaf weeds. Annual grasses may only be suppressed.  Use the lower rates on coarse-textured soils and soils low in organic matter; use the higher rates on fine-textured soils and soils high in organic matter. To avoid crop injury, do not use on sand or loamy sand soils, or apply if crop is under water stress.

For parsley, can be applied pre- and postemergence.  Do not exceed a seasonal maximum of 3 lb/A. Make a single preemergence broadcast application of Caparol up to 14 days after planting (after seeding, but before crop emergence) at the rate of 1.0 pt/A. Follow with overhead irrigation if rainfall does not occur.

For extended weed control, a second postemergence application can be made at 1.0 pt/A up to 30 days prior to harvest. A third application at 1.0 pt/A can be made to the regrowth up to 30 days prior to the second (cutting) harvest. Do not make more than 3 application per year at a maximum of 1 pt/A per application.

For cilantro, use preemergence only.  Make a single application of 2 – 3.2 pt/A of Caparol after seeding, but before cilantro emergence. Use the lower rates on coarse-textured soils and soils low in organic matter; use the higher rates on fine-textured soils and soils high in organic matter.

Herbicides Used Postemergence to Weeds

clethodim (Select Max): 14 day PHI, 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.

pelargonic acid (Scythe)1 day PHI, 12 hr REI, Group 27. 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): 15 day PHI, 12 hr REI, 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.