Weed Control

NOTE: This is a list of herbicides registered for use in rhubarb in New England, but there is no specific crop safety data or efficacy data available for these products on rhubarb in our region. Always use caution when using new products until you have a sense of how they will perform in your field conditions on your crop.

Preemergent Herbicides (before weeds germinate)

HRAC Group 5:

• prometryn (Caparol 4L): 2 to 4 pt/A; PHI 40d, REI 12h. 1 application per year. Apply when rhubarb is dormant, before leaf emergence.

HRAC Group 13:

• clomazone (Command 3ME): 64 fl oz/A; REI 12h. 1 application per year. Apply when rhubarb is dormant, before leaf emergence. Temporary partial whitening of leaf or stem tissue may occur but should not affect yield.

HRAC Group 14:

• sulfentrazone (Aquesta 4F): 8 fl oz/A; REI 12h. 1 application per year. Apply just before rhubarb plants break dormancy, at 80 days before harvest.

HRAC Group 15:

• s-metolachlor (Dual Magnum): 0.67 to 1.33 pt/A; PHI 62d, REI 24h. 1 application per year. Apply when rhubarb is dormant, before leaf emergence, as a broadcast spray to soil surface in early spring.

HRAC Group 29:

• dichlobenil (Casoron 4G): 50 lb/A; REI 24h. 1 application per year. Apply when rhubarb is dormant.

Pre- and Postemergent Herbicides

HRAC Group 2:

• halosulfuron (Sandea): 0.5 to 1 oz/A; PHI 60d, REI 12h. 1 application per year. Apply when rhubarb is dormant, as late as possible in the spring. Sandea may cause significant crop stunting; begin with the lower rate to determine potential sensitivity to its use along with speed and degree of recovery. 

HRAC Group 4:

• quinclorac (QuinStar 4L): Up to 12.6 fl oz/A; PHI 30 d, REI 12h. Do not exceed 25.2 fl oz/A per year. Do not apply to stressed crop or injury may occur.

HRAC Group 5:

• linuron (Lorox DF): Up to 3 lb/A; REI 24h. 1 application per year. Apply when rhubarb is dormant, before leaf emergence, as a broadcast or banded over-the-row treatment. 

HRAC Group 27:

• mesotrione (Callisto): 6 fl oz/A; PHI 21d, REI 12h. 1 application per year. Apply when rhubarb is dormant, before leaf emergence. Rainfall or irrigation after application may increase the risk of injury to emerging rhubarb. 

Postemergence Herbicides (after weeds germinate)

HRAC Group 0:

• pelargonic acid (Scythe): 3% to 10% solution; PHI 1d, REI 12h. Apply preplant, or as a directed and shielded spray during crop growth. Contact with crop will cause damage.

HRAC Group 1:

• clethodim (Select Max): 9 to 16 fl oz/A; PHI 30d, REI 24h. Do not exceed 64 fl oz/A per year. Apply to actively growing grasses.

• fluazifop (Fusilade DX): 6 to 16 fl oz/A; PHI 14d, REI 12h. Do not exceed 32 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 3 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 fl oz to 3.1 qt/A; PHI 14d, REI 4h. Do not exceed 5 qt/A per year. Rate based on target weed species. 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.

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. Apply as a preplant burndown no later than 1 day before transplanting crops, or with a hooded sprayer to row middles of emerged crops, including crops grown on mulch or plastic. Contact with crop will cause damage.

HRAC Group 22:

• paraquat (Gramoxone SL 3.0*): 1.7 to 2.7 pt/A; REI 48h. Do not exceed 5.4 pt/A per year. Apply when rhubarb is dormant, before leaf emergence. May be fatal if swallowed or inhaled. *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.