Weed Control

NOTE:  For the herbicides listed below, one product trade name and formulation is provided for each active ingredient as an example of rates, preharvest interval (PHI), restricted entry interval (REI), resistance management group number, 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. 

Grass Weed Control - new plantings and established beds

clethodim (Select Max): PHI 1d, REI 24h, Group 1.  Apply 9 to 16 oz/A per application, minimum 14 days between applications.  Do not exceed 64 oz/A per year.  Will control grass weeds only. Apply to actively growing grasses (see product label for susceptible stage). Add 1 qt nonionic surfactant per 100 gal of spray (0.25% v:v).  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 1d, REI 12h, Group1.  For grass weed control only. 16 to 24 oz/A per application, minimum 14 days between applications, and not to exceed 48 oz/A per year.  Will control grass weeds only. 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).

sethoxydim (Poast): PHI 1d, REI 12h, Group 1.  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.

New Plantings

glyphosate (Roundup Power Max): REI 12h, Group 9. Preplant or stale seedbed application. Rate depends on target weeds, see label for rate selection. See Stale Seedbed Technique, page 107.

paraquat (Gramoxone SL 2.0*): restricted use. REI 12h, Group 22. Use 2.5 to 4 pts/A.  Preplant or stale seedbed application. See Stale Seedbed Technique, page 107. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training.... The training must be completed a minimum of every three years.

pelargonic acid (Scythe): PHI 1d, REI 12h, Group 17. Use a 3% to 10% solution (3 to 10 gallons per 100 gallons).  See Stale Seedbed Technique, page 107.

pendimethalin (Prowl H2O)PHI 14d, REI 24h, Group 3. Can be applied to newly planted crowns but NOT to newly seeded crop.  When applying to newly planted crown asparagus, assure crowns are fully covered with 2 to 4 inches of soil.  Do not apply over the top of emerged spears or injury will occur.  Use as a single application of up to 8.2 pt/A.  On sandy soils do not use more than 2.4 pt/A.  Apply uniformly to the soil surface at least 14 days prior to the first harvest.  Cultivate or use Gramoxone to control emerged weeds. 

linuron (Lorox DF): PHI 1d, REI 24h, Group 5. Can be used for pre- and postemergence control of many annual broadleaf weeds.  See label for instructions on preemergence use after planting. For postemergence weed control, use 1 to 2 applications of 1 to 2 lbs/A when ferns are more than 6 inches tall.  Spray emerged weeds when they are less than 4 inches tall. Use the lower rate on coarse-textured (sandy) soils low in organic matter, and the higher rate on fine-textured (silt and clay) soils. A second application can be made 1 to 3 months after the initial application, not to exceed a total of 4 lbs/A per year.

Established Beds – Before spear emergence or after harvest season

clomazone (Command 3ME): PHI 14d, REI 12h, Group 13.  Make a single application of 42.7 fl oz/A in at least 10 gallons of water per acre prior to spear and weed emergence or after a clean harvest (must cover all asparagus plant parts with soil to prevent injury).  Will control annual grasses and many broadleaf weeds.

diuron (Karmex DF, Diuron 4L): REI 12h, Group 5. Karmex not registered in NH and VT. Diuron 4L registred in all New England States. Use lower rates on light sandy soils (and other soils low in clay and organic matter) and higher rates on soils high in clay or organic matter. Use in the spring preemergence to both crop and weeds.  If necessary, a second application can be made after cutting season.  If planning two applications, do not exceed 3 lbs/A per application.  The soil must be kept moist to activate diuron. If weeds start to germinate, cultivate lightly (not deeper than 1") and irrigate during cutting season. Do not use on newly seeded asparagus or on young plants or crowns during the first season. Do not use diuron on a bed the year it is to be abandoned and planted to another kind of vegetable.

flumioxazin (Chateau SW)REI 12h, Group 14.  Apply 3 to 6 oz/A per application, not to exceed 6 oz/A per season. For post-harvest applications, apply at least 2 weeks before fern emergence.  For preemergence use, apply at least 14 days before spears emerge.  Must be sprinkler or rainfall incorporated (0.5 to 0.75” of water) for preemergence weed control.  Will control many broadleaf weeds and some grass species.  If soil has been disturbed prior to application or if asparagus is not dormant, some crop injury may be observed.  Can be applied to dormant asparagus tank-mixed with Gramoxone for burndown of emerged weeds.  Use as an alternative to metribuzin, diuron, or terbacil.  Do not use every year. Limited data on efficacy and crop safety for use in the New England region.

linuron (Lorox DF): PHI 1d, REI 24h, Group 5. Can be used as a single 2 to 4 lb/A application for preemergence weed control.  Apply prior to spear emergence or after harvest for residual and postemergence control of many annual broadleaf weeds.  Use the lower rate on coarse-textured (sandy) soils low in organic matter, and the higher rate on fine-textured (silt and clay) soils.  See information about postemergence use in the following "Established Beds - Postemergence" section.

mesotrione (Callisto)REI 12h,  Group 27.  Apply 3 to 7.7 oz/A.  See lable to select appropriate rate for weeds and timings. Can be applied in the spring prior to spear emergence, or after harvest, or both, to control many winter and summer annual broadleaf weeds.  Maximum of two application permitted, minimum 14 days between applications, not exceed a total of 7.7 oz/A per year. When using Callisto after harvest, till the field or tank-mix with Gramoxone to eliminate emerged spears or crop injury may be observed as white or white streaks in the stems and fern when treated spears grow.  Callisto provides excellent control of horseweed (also called marestail or stickweed), including glyphosate-tolerant strains, and common lambsquarter. Callisto does not control most grasses.  Tank-mix Callisto with a residual annual grass herbicide to control annual grasses.  Add 1% crop oil concentrate (1 gal/100 gal of spray solution) or 0.25%  nonionic surfactant (1 qt/100 gal of spray solution) if target weeds are emerged at the time of application. 

metribuzin (Metribuzin 75): PHI 14d, REI 12h, Group 5.  Can be applied as a single application in the spring prior to spear emergence (1.3 to 2.6 lb/A), or as two applications in the spring and after harvest.  The total amount of metribuzin applied cannot exceed 2.6 lbs/A.  If using two applications, apply 0.6 – 1.3 lbs/A in the spring and 1.3 – 2.0 labs/A after harvest but before fern emergence.  If field is to be disked, apply after disking but before crop emergence. Do not use on newly seeded asparagus or on young plants or crowns during first season. Do not apply to established beds after emergence. Fair on grasses.

napropamide (Devrinol 2-XT): REI 12h, Group 0. Use up to 2 gal/A. Incorporate thoroughly with irrigation prior to spear emergence if adequate rainfall does not occur within 24 hours of application. Apply only to stands that have been established for atleast one growing season.

norflurazon (Solicam DF): PHI 14d, REI 12h, Group 12. Apply 2.5 to 5 lb/A, select rate based on soil type.  See label for details.  If adequate rainfall does not occur within 4 weeks of application, irrigation should be used to incorporate and activate. Apply after the cutting season. Controls most grasses and several broadleaf weeds. Also will suppress yellow nutsedge. Cannot be used unless planting is at least 12 months old, and should not be used if a crop rotation is planned within 24 months.

paraquat (Gramoxone SL 2.0*): restricted use. PHI 6d, REI 12h, Group 22. Use 2.5 to 4 pts/A, up to three applications per year. Apply prior to emergence of crop at least 2 years old, or after last clean cut harvest. Asparagus plants that have emerged at time of application will be killed. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training.... The training must be completed a minimum of every three years.

pendimethalin (Prowl H2O)PHI 14d, REI 24h, Group 3. Apply before spear emergence or after harvest.  Do not apply over the top of emerged spears or injury will occur.  Use as a single application of up to 8.2 pt/A.  On sandy soils do not use more than 2.4 pt/A.  Apply uniformly to the soil surface at least 14 days prior to the first harvest.  Cultivate or use Gramoxone Inteon to control emerged weeds. 

terbacil (Sinbar WDG): PHI 5d, REI 12h, Group 5. Apply prior to spear emergence, after a clean cutting, or after the last harvest.  Do not apply more than 1.5 lb/A per application, and if more than one application is made, total rate cannot exceed 2.5 lb/A per year. Use a lower rate on coarse-textured soils.  Do not apply if roots are exposed or if the planting is weak; see label.

trifluralin (Treflan HFP): REI 12h, Group 3. Established plantings only. Can be used in the spring prior to spear emergence, after harvest before ferns emerge, or both. Rate based on soil texture and number of planned applications, see label for details. 

Established Beds - Postemergence to weeds

clopyralid (Clean Slate): PHI 48h, REI 12h, Group 4. Other clopyralid formulations may not labeled. Apply 0.5 to 0.67 pt/A. Two applications can be made as long as the total amount applied per year does not exceed 0.67 pts/A. Applications may be made before or during the asparagus cutting season, or after harvest is complete but prior to fern growth. Use the higher rate for more effective control of perennial weeds. Can control or suppress sensitive annual and perennial broadleaf weeds, including Canada thistle, goldenrod, mugwort, and wild aster species. For annual weeds, apply before flower stalks of weeds emerge. For perennial weeds, apply when majority of weeds’ basal leaves have emerged. Some crooking or twisting of treated spears may occur. Do not apply if some crooking of emerged spears is not acceptable. Clear-cutting spears just before applying may reduce occurrence of crooking. Post-harvest layby applications should be made as soon as possible after cutting. Malformed ferns may result from application when spears are longer than 3 inches or with open seed heads. Spur carryover may affect subsequent crops; observe all plantback restrictions list on label. Can be tank mixed with other herbicides. See the label for tank mixing guidance.

dicamba (Clarity): PHI 24h, REI 24h, Group 4. Apply 8 to 16 fl oz/A to emerged and actively growing weeds immediately after cutting field but at least 24 hrs before next cutting. Multiple applications can be made, but do not exceed 16 fl oz/A per year total. If spray contacts emerged spears, crooking (twisting) of some spears may result. If crooking occurs, discard affected spears.

glyphosate (Roundup Power Max): REI 12h, Group 9. Apply to emerged weeds well before spear emergence in the spring as contact with spears will result in serious crop injury.  Can also be applied after cutting season, after removal of all growing spears and fern (clean cut). Contact with growing spears or fern will result in crop injury. For later application use directed or shielded sprays to prevent plant contact. Rate depends on target weeds, see label for rate selection.

halosulfuron (Sandea): PHI 1d, REI 12h, Group 2. For transplanted crowns and established beds only. For transplanted crowns, apply no sooner than 6 weeks after fern emergence. For established beds, apply before or during harvest season. May also be applied as a directed spray to the base of the ferns. Contact with ferns will cause yellowing. Will provide preemergence and postemergence control of many weeds. Use 0.5 to 1.5 oz/A per application. Do not apply more than 2 times per season and do not exceed 2 oz/A per year. See label for list of weeds and other precautions.  Weed control may be reduced without the use of a surfactant.

linuron (Lorox DF): PHI 1d, REI 24h, Group 5. Use 1 to 3 applications of 1 – 2 lbs/A for postemergence weed control.  Spray emerged weeds when they are less than 4 inches tall. Use the lower rate on coarse-textured (sandy) soils low in organic matter, and the higher rate on fine-textured (silt and clay) soils. DO NOT exceed 4 pounds of product per acre per year total (including any preemergence applications).  See information about preemergence use in the previous "Established Beds – Before spear emergence or after harvest season" section.

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. These include tank mixes with glyphosate (Roundup), sulfosate (Touchdown), and residual herbicides. See label for complete details.

s-metolachlor (Dual Magnum): REI 12h, Group 15.  MASSACHUSETTS, MAINE, and NEW HAMPSHIRE ONLY. Make sure the label for your state is available for download before using this product. This is a restricted label available only to growers who apply through the website www.syngenta-us.com/labels/indemnified-label-login 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.

2,4-D sodium salt (Amine 4): PHI 3d, REI 48h, Group 4.  Use 3 - 4 pt/A.  Two applications are permitted, a minimum of one month apart.  Spot spray when weeds appear. Keep spray off spears and ferns. 2,4-D is hazardous to most horticultural crops. Drift or sprays may seriously injure or reduce yields of these crops. May help to control unwanted seedling asparagus.

 

Note About Other Labeled Herbicides: Other products are labeled for use in asparagus but limited local data are available for these and/or they are not recommended in our region due to potential crop injury concerns. These include quinclorac (QuinStar), carfentrazone (Aim), sulfentrazone (Zeus and others), and diquat (Reglone).