Pumpkin Field Preparation

There have been quite a few calls this year coming into the office asking about herbicides for pumpkins. It seems that some weeds are getting away from people which could be from resistance issues, timing problems, or just a general need to incorporate a new chemistry into the mix.

As with any recommendation, proper weed identification is essential. Knowing whether you are dealing with a perennial or annual, or a grass, sedge, or broadleaf species, helps explain why a program may not be performing as expected. The goal of this article is to address practical application and herbicide selection questions that have come up recently.

Can you suggest a spray routine for bareground pumpkin?

A good place to start is always the Mid-Atlantic Commercial Vegetable Production Guide (2026–2027 edition). It is still important to cross-reference product labels to ensure the program fits your planting schedule.

After tillage and soil preparation, commonly used products include Strategy 2.1 SC (ethalfluralin + clomazone; 3-4 pts/A) and Sandea 75DF (halosulfuron; 0.5–0.75 oz/A) plus an additional 8-10 fl oz Curbit for longer grass control. On heavier soils Strategy 2qts/A and Command 3ME 0.67pt/A

Strategy is a combination product that can cause some confusion, particularly around timing. Because it contains ethalfluralin (also found in Curbit), we defer to that label: apply after seeding but before crop emergence and do not incorporate. Note that Strategy does not control sedges. Sandea is included to help with sedges and some broadleaf weeds that aren’t picked up by Strategy. The Sandea label states it should be applied after seeding but before emergence making it a nice addition to the Strategy.

If you have been using the program above and still finding certain weeds difficult to control, consider include Reflex 2SL (fomesafen, 1–1.5 pts/A) with strategy to broaden weed control. Reflex can be effective on stubborn weeds but may also cause crop damage. Like Strategy and Sandea, it must be applied after seeding, specifically within 24 hours, and should be followed with irrigation or rainfall.

For grass escapes, selective postemergence herbicides can be applied over the top of pumpkins. These include clethodim (Select Max; 9–16 fl oz/A) and sethoxydim (Poast 1.5 EC; 1–1.5 pts/A).

If certain broadleaf weeds are escaping from initial treatment, you will have one more opportunity to apply Sandea. It must be applied before flowering, while plants have 3-5 true leaves. Any earlier will cause crop damage. You can only make two applications of Sandea and there are no other broadleaf weed chemistries for post emergence applications. Sandea is week on lambsquarters, nightshade, and purslane, when used as a post emergent. However, it is useful for yellow nutsedge, common ragweed, redroot pigweed, and velvetleaf.

At approximately the 5-leaf stage, applying straw mulch can help suppress weeds, conserve moisture, and protect fruit from soil contact. Some growers blow straw over the planting and come back later to free the pumpkin plants as needed with rakes.

If annuals or nutsedge are persistent issues, consider Dual Magnum (s-metolachlor; 0.67–1.33 pts/A) for future seasons. It provides longer residual control but is limited to row middles. Dual must be applied before weeds start to germinate.

Some growers may use burndown programs that include glyphosate and Group 4 herbicides such as 2,4-D prior to planting. While effective for site preparation, keep in mind that plant-back intervals for commonly used Group 4 herbicides labeled for crop production have plant back intervals of 3-4months for pumpkin depending on formulation and rate. This limits their legal use ahead of June-seeded pumpkins.

Can you suggest a spray routine for no-till pumpkin?

The general recommendations for planting no-till pumpkin are similar to those above with the added benefit of increasing soil organic matter and general soil health over time.

No-till pumpkin systems follow similar herbicide principles but rely on a cover crop, typically annual rye. A strong rye stand is important. In Western Pennsylvania no-till growers commonly seed at about 70 lb/A.

Begin terminating the rye about 2 weeks prior to your anticipated seeding date. The rye is first sprayed with glyphosate. Depending on the weed coverage within the rye, you may try to set the boom low and get the spray into the weeds within the rye. Run your tractor the same direction for each spray pass if you don’t have tire lanes. This way the rye you run over falls in the same direction. For best results, allow 3–7 days for activity before rolling.

Lay down the rye with a roller-crimper 5–7 days before planting to create a uniform mulch. Plant using a no-till drill in the same direction the rye was rolled.

If rye coverage is thin or weeds break through, preemergence herbicides like Strategy, Reflex, or Sandea can still be used as in bareground systems.  If the rye is thick and well matted, you may not need another herbicide applicaiton. However, you may want to be prepared for an application of Sandea, if nutsedge or broadleaf weeds are present, during the 3-5 leaf stage and before flowering. Clethodim and Poast can be used as needed over the top of pumpkins for grassy weeds.

Foxtails are getting away from me, what is wrong?

Foxtails are an annual grass. If they have been difficult to manage using Strategy as the primary pre-emergent, you might need to try Dual Magnum for longer control. Remember that Dual Magnum can only be used in row middles. Soil disturbance or very heavy rain events can impact the efficacy of all pre-emergent herbicides. After application, be careful not to disturb the soil. Foxtails can also be treated in season with postemergence grass herbicides such as sethoxydim or clethodim before seed set.

Cocklebur is my primary issue, what is wrong?

Cocklebur is one of the broadleaf species that is not controlled well by Strategy alone. By adding Sandea to your schedule either as a both a soil applied pre-emergent and post emergent before flowering, you should see better control of cocklebur.

Yellow Nutsedge is a persistent issue, what should I do?

Sandea is the primary in season chemistry that will work on nutsedge without resorting to targeted, hooded, spot treatments of glyphosate. If applied only postemergence, control with Sandea may be limited to suppression especially in fields with heavy nutsedge. Using one application before seedling emergence and another prior to flowering provides better overall control. After harvest, treating regrowth with glyphosate can help move herbicide into underground nutlets. Dual Magnum can provide control of yellow nutsedge in row middles when applied as a preemergent early, and with good activation from rainfall or irrigation.

Canada Thistle is always my issue, what can I do?

Canada thistle is a perennial with an extensive root system, making it difficult to control. Glyphosate applications made in the spring will only provide a limited knockdown effect and the plant will return later in the season.

For better control, apply glyphosate after harvest to take advantage of the downward movement of carbohydrates into roots as the plant prepares for dormancy. September through early November are the best times for these applications which should improve long-term suppression.

Marestail is my primary issue and nothing touches it.

Marestail can be particularly difficult to control in season; because most of the pumpkin herbicides such as Dual Magnum, Strategy, Command, Curbit, Sandea, Reflex, and Aim are not effective. Control is limited to row-middle applications of burn-down herbicides when marestail is small (i.e., less than 3 inches tall) to provide some control. Otherwise, tillage is an effective tactic, as well as plastic mulch in rows is adequate. However, these tactics are limited in bareground, mulched, and no-till production systems. A thick cereal rye cover crop mulch can suppress it and limit its ability to germinate as an annual throughout the season.