Onion, Scallion, and Shallot Weed Control

Onion, Scallion, and Shallot - General Onion, Scallion & Shallot Disease Control Onion, Scallion & Shallot Insect Control

Stale Seedbed

The following herbicides are nonselective and are used to control weeds that are present in a field prior to planting or before the crop emerges, which is especially useful for the Stale Seedbed Technique (see the Weed Management section for more information).

glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
paraquat (Gramoxone SL 2.0*): PHI 60d, REI 48h, Group 22. *Restricted use: Applicators must complete an EPA-approved paraquat training every 3 years: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.
pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

HRAC Group 0:

bensulide (Prefar 4E): 5 to 6 lb/A; REI 12h. Dry bulb onion and dry bulb shallot only, under optimum growing conditions only. 1 application per year. Apply before transplanting. Grass control only.

HRAC Group 3:

pendimethalin (Prowl H2O): 1.5 to 3.2 pt/A; PHI 45d, REI 24h. Dry bulb onions and shallots only. Do not exceed 3.2 pt/A per year. May be applied to direct-seeded and transplanted dry bulb onions. Apply as a broadcast treatment when onions have 2–9 true leaves; in the fall or spring as a banded application to beds to be planted in the spring; or as a banded application to flag-leaf onions.
trifluralin (Treflan HFP): 0.75 to 1 pt/A; PHI 60d, REI 12h. Dry bulb onions only. 1 application per year. Apply between rows at layby, after onions have emerged. Two incorporation passes are required, the first within 24 hours of application, the second at least 5 days after the first. Contact of spray or treated soil with crop will cause damage. Applications made to stressed onions may lead to crop damage.

HRAC Group 15:

dimethenamid (Outlook): 7 to 21 fl oz/A; PHI 30d, REI 12h. Dry bulb onions and dry bulb shallots only. Do not exceed 21 fl oz/A per year. See label for single vs. split application rates. Apply to crops that have at least 2 fully expanded leaves. If applying to transplants, do not apply until transplants are in the ground and have had several days to recover.
s-metolachlor (Dual Magnum): PHI 60d, REI 24h. MA, ME, and NH only. Dry bulb onions and green onions only. Restricted label: Make sure the label for your state is available for download before using this product. Full label instructions are supplied 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.

Pre- and Postemergent Herbicides

HRAC Group 14:

oxyfluorfen (Goal 2 XL): 2 to 4 fl oz/A; PHI 45d, REI 48h. Dry bulb onions only. Do not exceed 2 pt/A per year. Apply when direct-seeded onions have 3 true leaves or immediately after transplanting. Spray additives not recommended.

Postemergent Herbicides (after weeds germinate)

HRAC Group 0:

pelargonic acid (Scythe): 3% to 10% solution; PHI 1d, REI 12h. Onion and shallot only. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth, or as a harvest aid and desiccant to remove crop leaves or ease harvest. Contact with crop will cause damage.

HRAC Group 1:

clethodim (Select Max): 9 to 32 fl oz/A; PHI 45d, REI 24h. Dry bulb onions and shallots only. Do not exceed 64 fl oz/A per year. Apply to actively growing grasses.
fluazifop (Fusilade DX): 6 to 24 fl oz/A; PHI 45d for bulb onion and shallot, 14d for scallion, REI 12h. Do not exceed 48 fl oz/A per year. Apply to actively growing grasses.
sethoxydim (Poast): 0.5 to 1.5 pt/A; PHI 30d, REI 12h. Do not exceed 4.5 pt/A per year. Apply to actively growing grasses. BASF has stopped production and will discontinue the registration at the end of 2027.

HRAC Group 9:

glyphosate (Roundup Power Max): 10 oz to 3.1 qt/A; PHI 14d, REI 4h. Do not exceed 5 qt/A per year. Apply during fallow intervals, prior to planting, at planting, before crop has emerged, or to row middles with a hooded or shielded sprayer or wiper applicator. Spray contact can cause crop death. Spray additive recommendation varies with formulation—see label.

HRAC Group 14:

carfentrazone (Aim EC): 0.5 to 2 fl oz/A; PHI 0d, REI 12h. Do not exceed 6.1 fl oz/A per season. Can be applied as a preplant burndown no later than 30 days before planting by seed, or to row middles of emerged crops with hooded sprayers. Contact with crop will cause damage.

HRAC Group 22:

paraquat (Gramoxone SL 2.0*): 1.3 to 2.7 pt/A; PHI 60d, REI 48h. Onion only. 1 broadcast application before crop emergence, and 1 directed spray application after crop emergence allowed. Do not exceed 4 pt/A per year. May be fatal if swallowed or inhaled. *Restricted use: Applicators must complete an EPA-approved paraquat training: https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators.

HRAC Group 24:

bromoxynil (Broclean): 1 to 1.5 pt/A; PHI 30d, REI 12h. Onions only. 1 application per year. Apply to onions with 2–5 true leaves. Concentrated Broclean will kill onions; apply in at least 50 gal/A of spray. If the waxy coating on onion leaves is insufficient, Broclean can kill onions. Do not add a surfactant.

Weed Control