Weed Control

No-Till

Based on work done in New York State, it may be possible to achieve good weed suppression by allowing winter rye to grow to 30", killing it with glyphosate (Roundup), and then seeding pumpkins or squash with a no-till planter. Remember that if weed suppression is not adequate, cultivation will be very difficult in the rye stubble. Any of the herbicides registered for postemergence control can be used in no-till pumpkins to control weeds not suppressed by the killed cover crop. Preemergent herbicides can also be applied over the top of a terminated cover crop. Their activity will be reduced due to interception from the cover crop, however, they will add residual weed control in areas where cover crop biomass is light and in this way using the cover crop in conjunction with the preemergent herbicide, overall weed control will be improved.

Stale Seedbed

The following herbicides are nonselective and are used to control weeds which 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*): 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 qt/A. REI 12h. 1 application per year. Can be applied to flat-bedded or bedded crops. May be used under plastic. Grass control only. 

HRAC Group 3:

• ethalfluralin (Curbit EC): 3 to 4.5 pt/A. REI 24h. 1 application per year. Apply up to 2 days after seeding but before the crop emerges, or as a banded spray between rows after crop emergence or transplanting. Do not use during cold, wet weather or crop injury may occur.

HRAC Group 13:

• clomazone (Command 3ME): 10.7 to 32 fl oz/A. PHI 30d for summer squash, 45d for winter squash and pumpkins, REI 12h. 1 application per year. Broadcast apply prior to direct-seeding or transplanting, or between plasticulture beds. Temporary partial whitening of leaf or stem tissue may occur but should not affect yield. Do not apply to soil that will be covered by black plastic. Do not apply to Jack-o-lantern pumpkins or Cucurbit maxima squash that have pink or burnt orange color at harvest. 

HRAC Group 15:

• s-metolachlor (Dual Magnum): 1 to 1.33 pt/A. PHI 30d, REI 24h. Pumpkins only. 1 application per year. Apply banded between planted rows, leaving 6” of untreated soil to each side of the row. Do not apply directly over planted pumpkin seed or young pumpkin plants. Additional restricted label for pumpkin available in MA, NH, and ME only and for winter squash in MA, NH, and CT only. 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 2:

• halosulfuron (Sandea): 0.5 to 0.75 oz/A. PHI 30d, REI 12h. Do not exceed 2 oz/A per year. Apply after direct-seeding but prior to soil cracking; no sooner than 7 days before transplanting crop; over-the-top, directed-spray, or with crop shields to direct-seeded or transplanted crops after the crop has 2-5 true leaves but before the first female flowers appear and no sooner than 14 days after transplanting; between beds, including plasticulture; using wiper applicator. Do not apply to emerged squash grown for seed (including edible seed).

HRAC Group 27:

• bicyclopyrone (Optogen): 2.6 to 3.5 fl oz/A. PHI 14d, REI 24h. Watermelons only. 1 application per year. Apply before transplanting or to row middles. Contact with crop will cause damage.

Postemergent Herbicides (after weeds germinate)

HRAC Group 0:

• pelargonic acid (Scythe): 3 to 10% solution. PHI 1d, REI 12h. Apply as vegetative burndown prior to seeding or transplanting, after direct-seeding but prior to crop emergence, 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 14d, REI 24h. Do not exceed 64 fl oz/A per year. Apply to actively growing grasses.

• sethoxydim (Poast): 0.5 to 1.5 pt/A. PHI 14d, 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. Apply during fallow intervals and up until 3 days 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. Apply as a preplant burndown no later than 7 days before direct-seeding or 1 day before transplanting, or to row middles of emerged crops with hooded sprayers, including crops grown on plastic mulch. Contact with crop will cause damage.

HRAC Group 22:

• paraquat (Gramoxone SL 2.0*): 1.3 to 2.7 pt/A. REI 48h. Do not exceed 6.6 pt/A per year. Apply banded or broadcast, before transplanting or before, during, or after seeding but before crop 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.