Weed Control

NOTES: 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 9-16 oz/A per application, multiple applications are allowed, a minimum of 14 days apart. Do not exceed 64 oz/A per year. Apply to actively growing grasses. Add 1 qt nonionic surfactant per 100 gal of spray (0.25% v:v). Can also be applied as a spot-spray by mixing 1/3-2/3% (0.44-0.85 oz/gal) Select Max and 0.25% v:v nonionic surfactant (0.33 oz/gal). Spray to wet, but do not allow runoff of spray solution.
• fluazifop (Fusilade DX): PHI 1yr for high max rate or 1d for low max rate, REI 12h, Group1. Apply 16-24 oz/A per application, multiple applications are allowed, a minimum of 14 days apart. Do not exceed 48 oz/A per year if harvesting this year or 72 oz/A per year if harvesting next year. Apply to actively growing grasses. Add either crop oil concentrate (0.5-1%, 0.5-1 gal per 100 gal of spray) or nonionic surfactant (0.25-0.5%, 1-2 qts per 100 gal of spray).
• sethoxydim (Poast): PHI 1d, REI 12h, Group 1. Apply up to 2.5 pt/A per application, multiple applications are allowed, a minimum of 14 days between applications. Do not exceed 5 pt/A per year. Apply to actively growing grasses. Use with crop oil concentrate (2 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% (1.3-1.9 oz/gal) Poast and 1% v:v crop oil concentrate (1.3 oz/gal). Spray to wet, but do not allow runoff of spray solution.

New Plantings

• diquat (Reglone): PHI 1yr, REI 24h, Group 22. Apply 1.5-2 pt/A per application. Only use during site preparation prior to planting. Spray weeds 1-6” tall, retreatment may be necessary to control established weeds. Apply in a minimum of 15 gal/A of spray. Do not allow spray to contact crop stems, foliage, or fruit.
• glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9. Apply 10 oz to 3.1 qts/A per application. Do not exceed 5 qts/A per year. Rate depends on target weeds, see label for rate selection. Avoid contact with any part of the asparagus or crop death could occur. May apply during fallow intervals, prior to crop planting, at planting, before crop has emerged, or immediately after cutting before spears have emerged.
• linuron (Lorox DF): PHI 1d, REI 24h or 8d, Group 5. Can be used for pre- and postemergence control of many annual broadleaf weeds. For preemergence, apply 1-4 lbs/A after applying activated charcoal in a 1” wide band above seeds or crowns. For postemergence weed control, apply 1-2 lbs/A per application, up to 2 applications. Do not exceed 4 lbs/A per year. Spray when ferns are more than 6” tall and weeds are less than 4” tall. Use the lower rate on sandy soils and the higher rate on silt and clay soils.
• paraquat (Gramoxone SL 2.0*): restricted use. PHI 6d, REI 12h or 24h, Group 22. Apply 1.7-2.7 pt/A per application, only 1 application allowed per year. Can be applied before planting or as a stale seedbed application in a minimum of gal/A of spray. 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 0. Apply a 3-10% solution (3-10 gallons per 100 gallons of spray). Apply in 75-200 gal/A of spray. Can be applied preplant, or as a directed and shielded spray during crop growth. Avoid contact with foliage or crop damage may occur. Spray to wet, but do not allow runoff of spray solution.
• pendimethalin (Prowl H2O): PHI 14d, REI 24h, Group 3. Apply 8.2 pt/A, only 1 application allowed per year. Can be applied to newly planted crowns but NOT to a newly seeded crop. When applying to newly planted crown asparagus, ensure crowns are fully covered with 2-4” of soil. Do not apply over the top of emerged spears or injury will occur. On sandy soils do not use more than 2.4 pt/A. Apply uniformly to the soil surface, cultivate or use Gramoxone to control emerged weeds.
• terbacil (Sinbar WDG): PHI 5d, REI 12h, Group 5. Apply 1-2 lbs/A per application, multiple applications are allowed. Do not exceed 2.5 lbs/A per year. Direct seed asparagus 1.5-1” deep, then apply activated charcoal in a 1” wide band above seeds or crowns and then apply Sinbar WDG. Use a lower rate on sandy soils.
• trifluralin (Treflan HFP): REI 12h, Group 3. Apply 1-4 pts/A per application, multiple applications allowed. Do not exceed 4 pts/A per year. Apply prior to planting or immediately after planting seed and prior to crop germination. Can also apply and incorporated at or before the last cultivation. Rate depends on soil texture and percent organic matter. Incorporate within 24 hours of application and a second time in the opposite direction for best results. Take care not to bring untreated soil to the soil surface during re-incorporation.

Established Beds – Before spear emergence or after harvest season

• carfentrazone-ethyl (Aim EC): PHI 5d, REI 12h, Group 14. Apply 0.5-2 oz/A per application, 2 applications allowed per year, a minimum of 20 days apart. Do not exceed 3.8 oz/A per year. Apply as a hooded application, or as a broadcast application after harvest to control broadleaf weeds and existing asparagus tissue.
• clomazone (Command 3ME): PHI 14d, REI 12h, Group 13. Apply 42.7 oz/A, only 1 application allowed per year. Apply prior to spear and weed emergence or after a clean harvest (must cover all asparagus plant parts with soil to prevent injury) in at least 10 gal of spray per acre.
• diuron (Diuron 4L): REI 12h, Group 5. Apply 0.8-3.2 qts/A if 1 application is made or apply 0.8-2.4qts/A per application if 2 applications are made. Do not exceed 4.8 qts/A per year. Use the lower rate on sandy soils and the higher rate on silt and clay soils. Can be applied before weeds become established but no earlier than 4 weeks before spear emergence and no later than the early cutting period. A second application can be applied immediately following the final harvest if rainfall is expected.
• flumioxazin (Chateau SW): REI 12h, Group 14. Apply 6 oz/A per application, only 1 application allowed per year. Must be applied to dormant asparagus post-harvest, at least 2 weeks before spear emergence. If soil has been disturbed within 60 days prior to application or if asparagus is not dormant, crop injury may be observed. Must be sprinkler or rainfall incorporated (0.5 to 0.75” of water). Can be tank-mixed with Gramoxone for burndown of emerged weeds.
• linuron (Lorox DF): PHI 1d, REI 24h, Group 5. Can be used for pre- and postemergence control of many annual broadleaf weeds. Before spears emerge, apply 1-4 lbs/A per application. Do not exceed 4 lbs/A per year, (including applications after spear emergence). Use the lower rate on sandy soils and the higher rate on silt and clay soils.
• mesotrione (Callisto): REI 12h, Group 27. Apply 3 to 7.7 oz/A per application, a maximum of 2 applications allowed per year, a minimum of 14 days between applications. Do not exceed 7.7 oz/A per year. Can be applied in the spring prior to spear emergence, or after harvest, or both. When using Callisto after harvest, till the field or tank-mix with Gramoxone to eliminate emerged spears or crop injury may be observed. Callisto provides excellent control of horseweed (also called marestail) and common lambsquarters. Add 1% crop oil concentrate (1 gal per 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. Apply 1.3 to 2.6 lb/A in the spring as a single application or apply 0.6 to 1.3 lbs/A in the spring and 1.3 to 2.0 lbs/A after harvest but before fern emergence as a split application. Do not exceed 2.6 lbs/A per year. Do not apply to established beds after emergence.
• napropamide (Devrinol 2-XT): REI 24h, Group 0. Apply up to 2 gal/A, only 1 application allowed per year. Apply to a weed-free soil surface. Incorporate with 2-4” of water through irrigation or rainfall within 24 hours of application.
• norflurazon (Solicam DF): PHI 14d, REI 12h, Group 12. Apply 2.5 to 5 lb/A, multiple applications per year are allowed, but maximum rate per year is based on soil texture. Incorporate and activate with water through irrigation or rainfall within 4 weeks of application. Apply as a directed spray to the soil.
• paraquat (Gramoxone SL 2.0*): restricted use. PHI 6d, REI 12h, Group 22. Apply 1.7 to 2.7 pts/A, only 1 application allowed per year. Apply prior to emergence of crop, 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 8.2 pt/A, only 1 application allowed per year. On sandy soils do not use more than 2.4 pt/A per year. Apply before spear emergence or after harvest. Do not apply over the top of emerged spears or injury will occur. Apply uniformly to the soil surface, cultivate or use Gramoxone to control emerged weeds. 
• quinclorac (Quinstar 4L): REI 12h, Group 4. Apply up to 12.6 oz/A per application, only 1 application allowed per year. Apply to the soil after the last harvest, before the first frost. Can add a crop oil concentrate. Apply in a minimum of 10 gal/A of spray. Do not apply when crops are stressed. 
• sulfentrazone (Aquesta 4F): REI 12h, Group 14. Apply 4.5-12 oz/A per application, only 1 application allowed per year. Rate based on soil texture, organic matter and soil pH. Apply to the soil in the spring, before spears have emerged in 10-40 gal/A of spray. Do not use on soils that have less than 1% organic matter.
• terbacil (Sinbar WDG): PHI 5d, REI 12h, Group 5. Apply 1 to 1.5 lbs/A per application, multiple applications are allowed. Do not exceed 2.5 lbs/A per year. Apply after a clean cutting or after the last harvest, prior to spear emergence. Use a lower rate on coarse-textured soils. Do not apply if roots are exposed or if the planting is weak.
• trifluralin (Treflan HFP): REI 12h, Group 3. Apply 1 to 4 pts/A per application, multiple applications allowed. Do not exceed 4 pts/A per year. Apply to as a single or split application to dormant asparagus in winter or early spring after mature ferns have been removed. Do not apply immediately after harvest in late spring/early summer just before ferns develop. Rate depends on soil texture and percent organic matter. Incorporate within 24 hours of application and a second time in the opposite direction for best results. Take care not to bring untreated soil to the soil surface during re-incorporation.

Established Beds - After spears emerge

• 2,4-D sodium salt (Amine 4): PHI 3d, REI 48h, Group 4. Apply 3-4 pt/A per application, up to 2 applications allowed per season, a minimum of 1 month apart. Do not exceed 4.2 pts/A per year. Apply in 50-60 gal/A of spray in the spring. Keep spray off spears and ferns by using drop nozzles. Cut and discard any malformed spears immediately. 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.
• clopyralid (Clean Slate): PHI 48h, REI 12h, Group 4. Apply 0.5-0.67 pts/A per application, up to 2 applications allowed per year. Do not exceed 0.67 pts/A per year. Apply before or during the asparagus cutting season or after the final harvest but before fern growth. Following application, wait at least 2 weeks before cultivating. Layby applications should be made as soon as possible after cutting as long as weeds are at the proper stage of growth. Malformed ferns may result from application when spears are more than 3" tall or with open seed heads. When this product is applied during the cutting season, some crooking (twisting) of asparagus spears may occur. Do not apply during the cutting season if crooking cannot be tolerated. Clear-cutting of spears just before applying this product may reduce the occurrence of crooking.
• dicamba (Clarity): PHI 24h, REI 24h, Group 4. Apply 8 to 16 fl oz/A per application, multiple applications allowed. Do not exceed 16 fl oz/A per year. Apply to emerged and actively growing weeds immediately after cutting field but at least 24 hrs before next cutting. If spray contacts emerged spears, crooking (twisting) of some spears may result. If crooking occurs, discard affected spears.
• glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9. Apply 10 fl oz to 3.1 qts/A per application. Do not exceed 5 qts/A per year. Apply to emerged weeds well before spear emergence in the spring or after cutting season when all spears and ferns have been removed (clean cut). Avoid contact with any part of the asparagus or crop death could occur. Rate depends on target weeds, see label for rate selection.
• halosulfuron (Sandea): PHI 1d, REI 12h, Group 2. Apply 0.5 to 1.5 oz/A per application, up to 2 applications allowed per season. Do not exceed 2 oz/A per year. For transplanted crowns and established beds only. For transplanted crowns, apply no sooner than 6 weeks after fern emergence. For established beds, apply before, during, or at the end of harvesting season. May cause temporary stunting or twisting of ferns on certain varieties. Crop injury will decrease and weed control will improve when applied with a drop nozzel as a directed spray below the ferns. If targeting nutsedge, split applications during and after harvest are recommended. Use 0.75-1 oz per acre for each application at least 21-30 days apart, when nutsedge is targeted. Weed control may be reduced without the use of a surfactant.
• linuron (Lorox DF): PHI 1d, REI 24h, Group 5. Can be used for pre- and postemergence control of many annual broadleaf weeds. For postemergence weed control, apply 1-2 lbs/A per application, up to 3 applications, or 1 application of 4 lbs/A at the fern stage as a directed spray. Do not exceed 4 lbs/A per year (including applications before spear emergence). Spray when ferns are more than 6” tall and weeds are less than 4” tall. Use the lower rate on sandy soils low in organic matter, and the higher rate on silt and clay soils.
• pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. PHI 1d, REI 12h, Group 0. Apply a 3-10% solution (3-10 gallons per 100 gallons of spray). Apply in 75-200 gal/A of spray. Can use before planting, or as a directed and shielded spray during crop growth. Avoid contact with foliage or crop damage may occur. Spray to wet, but do not allow runoff of spray solution.
• s-metolachlor (Dual Magnum): REI 24h, 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.

There is limited local data available for quinclorac (Quinstar), carfentrazone (Aim), sulfentrazone (Aquesta), and diquat (Reglone). There may be potential crop injury concerns with use of these products in our region.