Weed Control : New England Vegetable Management Guide : UMass Amherst

NOTES: 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.

Garlic is not very competitive, so good weed control is critical. Mulch will control weeds and conserve moisture. If the mulch is removed, cultivation will likely be needed. It should be shallow so as not to damage roots.

Stale Seedbed

See Stale Seedbed Technique for information on the use of these herbicides or flaming.

glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
paraquat (Gramoxone SL 2.0*): restricted use. REI 12h or 24h, Group 22.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

bensulide (Prefar 4E): REI 12h, Group 0. Apply 5-6 qt/A per application, only 1 application allowed per year. Can be applied before planting or after planting before crop has emerged. Incorporate 1-2” into the soil within 36 hours by shallow cultivation or with water through irrigation or rainfall. Grass control only; should be supplemented with cultivation or another registered herbicide for broadleaf control.
dimethenamid (Outlook): PHI 30d, REI 12h, Group 15. Apply 8-21 oz/A, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 21 oz/A per year. If applying as a split application, apply half to two-thirds the rate at the first application and the remaining at the second application. Application rate depends on soil texture and organic matter content. Apply to garlic that have 2 fully expanded true leaves. Temporary leaf damage may occur and applying before the 2-leaf stage may cause significant crop injury.
flumioxazin (Chateau EZ): REI 12h, Group 14. Apply up to 6 oz/A per application, only 1 application per year. Apply within 3 days of planting garlic and before garlic has emerged. Incorporate into the soil with 0.5-0.75” of water through irrigation or rainfall.
s-metolachlor (Dual Magnum): REI 1d, Group 15. MASSACHUSETTS 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.
pendimethalin (Prowl H2O): PHI 45d, REI 24hr, Group 3. Apply 1.5-3.2 pt/A per application. Do not exceed 3.2 pt/A. Rate based on soil texture. Can be applied after planting but before crop emergence, after crop emergence when garlic is in the 1 to 5 true leaf stage, or at both timings. If applying before emergence, do not irrigate more than 0.5” of water until after loop stage.

Postemergent Herbicides (after weeds germinate)

bromoxynil (Broclean): PHI 112d, 60d in muck soil, REI 24h or 48h, Group 24. Apply 1.5-2 pts/A per application. Apply to garlic after emergence before it is 12” tall and before susceptible weeds are at the 4-leaf stage, 2” tall, or 1” wide.
carfentrazone (Aim EC): REI 12h, Group 14. Apply 0.5-2 oz/A per application, multiple applications allowed per year. Do not exceed 6.1 oz/A per season. Can be applied as a preplant burndown no later than 30 days before planting by seed. Can also be applied to row middles of emerged crops with hooded sprayers to control emerged weeds. Prevent any spray from contacting the crop, or injury will occur. For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across.
clethodim (Select Max): PHI 45d, REI 1d, Group 1. Apply 6-32 oz/A per application, up to 4 applications per year (2 if using 32 oz/A), a minimum of 14 days apart. Do not exceed 64 oz/A per year. Apply to actively growing grasses. Add 0.25% v:v nonionic surfactant (1 qt/100 gal of spray). Can also be applied as a spot-spray by mixing 0.33-0.66% (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 45d, REI 12h, Group 1. Apply up to 24 oz/A per application, up to 2 applications allowed per year, a minimum of 14 days apart. Do not exceed 48 oz/A per year. Apply to actively growing grasses. 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).
glyphosate (Roundup PowerMax): PHI 14d, REI 4h, Group 9. Apply 10 oz-3.1 qts/A per application but do not exceed 5 qts/A per year. Rate is dependent on target weed species. Avoid any contact of herbicide with foliage, green shoots, stems, bark, exposed roots, or fruit of crops, or crop death could result. Could cause injury when applied prior to transplanting or direct-seeding into plastic mulch. Remove residual product from plastic mulch with a 0.5’’ of water through irrigation or rainfall prior to planting. Can be applied during fallow intervals, prior to planting or transplanting, at planting, or before crop has emerged. For any crop not listed on the label, any application must be at least 30 days prior to planting.
oxyfluorfen (Goal 2 XL): PHI 60d, REI 48h, Group 14. For direct seeded garlic, apply 2-4 oz/A to garlic that has at least 3 fully developed true leaves. For transplanted garlic, apply 2-4 oz/A to garlic transplants as soon as possible after transplanting. Multiple applications allowed per year. Do not exceed 32 oz/A per year. For optimum control, apply when susceptible weeds are in the 2- to 4-leaf stage and actively growing. Application to weeds at later than 4-leaf stage may result in reduced weed control. Adjust nozzles for minimum spray contact with garlic plants, directing the spray to the soil at the base of garlic plants and adjacent bed top and furrow area. May cause chlorotic leaf banding, especially in cool wet conditions, but garlic will typically outgrow this damage.
paraquat (Gramoxone SL 3.0): restricted use. PHI 60d, REI 12h or 24h, Group 22. Apply 1.7–2.7 pts/A per application, only 1 application per year. Do not exceed 2.7 pts/A per year. Apply before crop has emerged as a broadcast application in a minimum of 10 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 17. Apply a 3-10% solution (3-10 gallons per 100 gallons of spray). Rate based on target weed species. Apply in 75-200 gal/A of spray or with a spot sprayer until foliage is wet but not to the point of runoff. Repeat applications as necessary. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth taking care to avoid contact with foliage and green tissue of crops, or after harvest. For beets, can also apply as a harvest aid to remove crop leaves.
sethoxydim (Poast): PHI 30d, REI 12h, Group 1. Apply up to 1.5 pt/A per application, multiple applications allowed per year, a minimum of 14 days apart. Do not exceed 4.5 pts/A per year. Apply to actively growing grasses. Use with crop oil concentrate (2 pt/A) or methylated seed oil (1.5 pt/A). Can also be applied 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.