Weed Control

NOTE:  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. 

 

No-Till and Stale Seedbed 

See Stale Seedbed Technique in the Weed Management section.

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 the 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.

See Stale Seedbed Technique in the Weed Management section. Prepare field 10 to 14 days prior to planting. Allow weeds to germinate. After seeding, but prior to crop emergence, then apply herbicides or flaming. 

glyphosate (Roundup Power Max): 12 hr REI, Group 9.

paraquat (Gramoxone SL 2.0*): restricted use. 12 hr REI, Group 22. Use 2 – 4 pts/A. 

pelargonic acid (Scythe): 1 day PHI, 12 hr REI, Group 27. Use a 3 -10% solution (3 to 10 gallons per 100 gallons).

 

Herbicides Used Preemergence to Weeds

bensulide (Prefar 4E): 12 hr REI, Group 8.  Apply 5 to 6 qt/A.  Can be preplant incorporated by shallow cultivation (1-2”) or applied preemergence and incorporated by irrigation within 36 hours or application. Good for annual grass control. See label for rotation restrictions. Can be used under plastic mulches.

clomazone (Command 3ME): 12 hr REI, Group 13.  Do not use on Jack-o-lantern pumpkins. Will control many broadleaf weeds including common lambsquarters, velvetleaf, and jimsonweed. Combining with Curbit will also control pigweed species. Some temporary crop injury (partial whitening of leaf or stem tissue) may be visible after crop emergence or after transplanting. See label for sensitive cultivars.  Complete recovery will occur from minor early injury without affecting yield or earliness. See label for replanting restrictions. For winter squashes, apply 0.67 to 2 pt/A prior to seeding or transplanting.  For summer squashes, apply 0.67 to 1.33 pt/A prior to seeding or transplanting. Use the lower rate on coarse soils and the higher rate on fine soils.

Do not apply to soil that will be covered with plastic mulch. Apply to row middles between plastic covered beds as a preemergence soil surface treatment before transplanting at rates as noted above.

ethalfluralin (Curbit EC): 24 hr REI, Group 3.  Can be used as a broadcast treatment. Do not use under mulches, row covers, or hot caps. May be banded between rows of plastic mulch. Do not soil incorporate prior to planting.  Apply to seeded crop at time of seeding or up to two days after seeding, or apply as a banded spray between rows after crop emergence.  A minimum of ½" of irrigation water (within two days after application) or ½” of rainfall (within five days of application) is required for activation. Use 3 to 4.5 pt/A, based on soil texture.  Rate will vary with the soil texture and organic matter. See label for rate selection. Use during cold, wet weather can result in crop injury or stunting. Some varieties are susceptible to injury or yield loss.

ethalfluralin + clomazone (Strategy): 24 hr REI, Group 3 and 13. Use 2 to 6 pt/A, based on soil texture.  See label for rate selection. Can be used as a broadcast treatment. Do not use under mulches, row covers, or hot caps. May be banded between rows of plastic mulch. Do not soil incorporate prior to planting.  Apply to seeded crop at time of seeding or up to two days after seeding, or apply as a banded spray between rows after crop emergence.  A minimum of ½" of irrigation water (within two days after application) or ½” of rainfall (within five days of application) is required for activation. Use during cold, wet weather can result in crop injury or stunting. Some varieties are susceptible to injury or yield loss.

s-metolachlor (Dual Magnum): This product has:

1. A full label that permits the use of Dual Magnum between rows of pumpkins.
2. An indemnified label for use over the top of pumpkins available in Massachusetts, Maine, and New Hampshire only
3. An indemnified label for use in Winter Squash available in Massachusetts, Connecticut, and New Hampshire only.

1. Full Label: 30 day PHI, 12 hr REI, Group 15.  Pumpkins only. Apply as a directed and shielded spray between the rows of plastic mulch or between bare ground rows in pumpkins to suppress or control annual grasses, yellow nutsedge, and certain annual broadleaf weeds including nightshade species.  Apply before the weeds have emerged at 1.0 to 1.33 pt/A as an inter-row or inter-hill application in pumpkin. Leave 1 foot of untreated area over the row, or 6 inches to each side of the planted hill and/or any emerged pumpkin foliage. Use the lower Dual Magnum rate on soils light in texture (loamy sand or lighter) and low in soil organic matter (less than 3%). Dual Magnum applied as a broadcast spray over the planted row or hill, or applications made directly to crop foliage will increase the risk of injury to the pumpkin crop such as stand loss, delayed maturity, and loss of yield. Will not control emerged weeds. Do NOT use Dual Magnum in winter squash, summer squash, or gourds.

 2. Indemnified label for Pumpkin - MASSACHUSETTS, MAINE, and NEW HAMPSHIRE ONLY. This is a restricted label available only to those growers who apply through the web site www.farmassist.com  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. Once on the farm assist web site, click products at top left, then indemnified labels.  Create a user name and password, select Dual Magnum, and the crop.

3. Indemnified label for Winter Squash - MASSACHUSETTS, CONNECTICUT, and NEW HAMPSHIRE ONLY. This is a restricted label available only to those growers who apply through the web site www.farmassist.com  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. Once on the farm assist web site, click products at top left, then indemnified labels.  Create a user name and password, select Dual Magnum, and the crop.

 

Herbicides Used Pre- and Postemergence to Weeds

halosulfuron (Sandea): 30 day PHI, 12 hr REI, Group 2. Use lower rates on lighter textured soils with low organic matter. Up to 2 application per year, not to exceed 2 oz/A total.

For pumpkins and winter squash: Apply 0.5 to 0.75 oz/A.

1. Direct seeded, Preemergence: Apply after planting, but prior to soil cracking.

2. Direct seeded, Postemergence: Apply after the crop has reached the 2 to 5 true leaf stage, preferably 4 to 5 true leaves, but before first female flowers appear.

3. Pre-transplant: Apply prior to transplant. Crop may be transplanted into this treated area no sooner than 7 days after application unless local conditions demonstrate safety at an earlier interval. Limit movement of Sandea treated surface soil during the transplanting process. If treated soils is moved into the transplant hole injury can occur.

4. Post-transplant: Apply to transplants that are established, actively growing and in the 3 to 5 true leaf stage, no sooner than 14 days after transplanting unless local conditions demonstrate safety at an earlier interval.  Apply before first female flowers appear. SANDEA can be applied as an over-the-top application, a directed spray application or with crop shields to minimize contact of the herbicide with the crop.

For pumpkins, winter squash, summer squash, and gourds:

1. Row Middle/Furrow Applications: Apply 0.5 to 1 oz/A between rows of direct seeded or transplanted crop while avoiding contact of the herbicide with the planted crop. If plastic is used on the planted row, adjust equipment to keep the application off the plastic.

 

Herbicides Used Postemergence to Weeds

carfentrazone (Aim EC): 12 hr REI, Group 14.  Aim is a burndown herbicide and will injure any foliage it comes into contact with. Apply Aim to row middles of emerged crops with hooded sprayers to control emerged weeds, including crops grown on mulch or plastic.  Prevent any spray from contacting the crop, or injury will occur.  For best results, make application to actively growing weeds up to 4 inches tall and rosettes less than 3 inches across. Good coverage is essential for good control.  Apply up to 2 oz/A per application, and do not exceed a total of 6.1 oz/ per season. 

clethodim (Select Max): 14 day PHI, 24hr REI, Group 1.  Will control grass weeds only. Apply to actively growing grasses.  See label for rate selection.  Multiple applications permitted of 9 to 16 oz/A per application, minimum 14-days between applications, not to exceed 64 oz/A per year.  Add 0.25% v:v nonionic surfactant (1 qt per 100 gal of spray).  Can also be used as a spot-spray by mixing 1/3-2/3% (0.44 to 0.85 oz per gallon) Select Max and 0.25% v:v nonionic surfactant (0.33 oz per gallon).  Spray to wet, but do not allow runoff of spray solution.

pelargonic acid (Scythe)1 day PHI, 12 hr REI, Group 27. Use a 3 -10% solution (3 to 10 gallons per 100 gallons). Use a 3 to 5% solution for annual weeds, a 5 to 7% solution for biennial and perennial weeds, and 7 to 10% solution for maximum burndown. Delivery rate for boom applications should be 75 to 200 gals of spray solution per acre; complete coverage of weed foliage is essential. Use a DIRECTED/ SHIELDED SPRAY; contact with crop will cause injury. For hand-held equipment, spray to completely wet all weed foliage but not to the point of runoff. Repeat applications as necessary. Tank mixes are allowed with this product. See label for complete details.

sethoxydim (Poast): 14 day PHI, 12 hr REI, Group 1.  Controls grass weeds only.  Apply to actively growing grasses (see product label for susceptible stage).  Maximum 1.5 pt/A per application, minimum 14-days between applications.  Do not exceed 3 pt/A per year. Use with crop oil concentrate (2.0 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 to 1.9 oz per gallon) Poast and 1% v:v crop oil concentrate (1.3 oz per gallon).  Spray to wet, but do not allow runoff of spray solution.  During periods of high temperature and/or high humidity some flowers may be damaged or dislodged and some foliar necrosis may result.