Nicosulfuron in Corn: Selective Post-Emergence Grass Weed Control That Works

Weed competition is one of the biggest yield-limiting factors in corn production—especially from annual and perennial grasses that establish early and rob the crop of nutrients, light, and water. For decades, post-emergence control has been a strategic part of maize weed management, and nicosulfuron has become one of the most trusted active ingredients in this category.

A systemic sulfonylurea herbicide, nicosulfuron offers selective control of key grass weeds in maize without harming the crop. Whether used alone or in tank mixes with complementary herbicides, it allows growers to target weeds at the most vulnerable stages, ensuring cleaner fields and stronger crop establishment.

In this article, we’ll explore how nicosulfuron works, what weeds it controls, how to apply it in maize fields, and what precautions to take for safe and effective use—especially if you’re sourcing or formulating nicosulfuron 40g/L SC or other combinations for your agricultural market.

What Is Nicosulfuron and How It Works in Corn

Nicosulfuron is a selective post-emergence herbicide belonging to the sulfonylurea chemical family, classified under HRAC Group B (ALS inhibitors). It is specifically designed to control a wide range of grass weeds and some broadleaf species in field corn (maize). Its systemic mode of action makes it a highly effective solution for early-season weed management.

Mode of Action

Nicosulfuron inhibits the enzyme acetolactate synthase (ALS), also known as acetohydroxy acid synthase (AHAS). This enzyme is essential for the synthesis of branched-chain amino acids (valine, leucine, isoleucine) in plants. When ALS is blocked:

• Cell division and growth stop rapidly

• Treated weeds cease development within hours

• Visible symptoms—such as chlorosis and necrosis—appear within 3 to 10 days

• Complete weed death typically occurs within 2 to 3 weeks

Because this enzyme is not present in animals, nicosulfuron has a favorable toxicological profile and can be used safely when applied according to label guidelines.

Selectivity in Corn

Nicosulfuron is absorbed mainly through the foliage and translocated throughout the weed. Corn plants metabolize the active ingredient rapidly, preventing herbicidal damage. This makes it safe to use on tolerant maize hybrids during specific growth stages—especially from V2 to V6 (2- to 6-leaf stage).

Target Weeds Controlled by Nicosulfuron

Nicosulfuron is particularly effective against a broad spectrum of annual and perennial grass weeds, which are among the most competitive and difficult to manage in corn fields. It also provides partial control of some broadleaf weeds, especially when tank-mixed with compatible herbicides.

Key Grass Weeds Controlled

• Echinochloa crus-galli (Barnyardgrass)

• Setaria spp. (Foxtail species: green, yellow, giant)

• Digitaria spp. (Crabgrass)

• Panicum spp. (Fall panicum, witchgrass)

• Sorghum halepense (Johnsongrass, seedling and rhizome forms)

• Lolium spp. (Ryegrass)

• Avena fatua (Wild oat) – at early stages

Broadleaf Weeds with Suppression or Partial Control

• Amaranthus spp. (Pigweed)

• Chenopodium album (Lambsquarters)

• Portulaca oleracea (Purslane)

• Polygonum spp. (Smartweed)

• Galinsoga parviflora (Gallant soldier)

For enhanced control of broadleaf weeds, nicosulfuron is often tank-mixed with atrazine, dicamba, mesotrione, or bromoxynil, depending on crop stage and regional regulation.

Weed Growth Stage Matters

Nicosulfuron is most effective when target weeds are small and actively growing, typically in the 2–4 leaf stage. Applications to mature, stressed, or drought-hardened weeds may reduce efficacy. For perennial weeds like Johnsongrass from rhizomes, early post-emergence treatment (15–30 cm height) is critical for suppression.

Application Timing, Rates, and Techniques in Corn

To maximize the effectiveness and crop safety of nicosulfuron, precise timing and application technique are essential. As a post-emergence systemic herbicide, it must be applied when both the corn crop and the target weeds are at appropriate growth stages.

Recommended Timing

• Corn growth stage: Apply when corn is at V2 to V6 stage (2 to 6 visible leaves)

• Weed growth stage: Apply when grasses are small (2–4 leaf stage) and actively growing

• Avoid application under stress conditions such as drought, cold temperatures, or after another herbicide that might weaken corn metabolism

Typical Application Rates

Always check local label recommendations, as rates may vary by country, crop type, and herbicide formulation.

Application Method and Carrier Volume

• Apply via ground sprayer or tractor-mounted boom, ensuring uniform coverage

• Use clean water, carrier volume of 200–400 L/ha for optimal leaf coverage

• Nozzles: Use flat-fan or air-induction nozzles to avoid drift

• Rainfastness: Rain within 2–4 hours may reduce efficacy—ensure adequate dry time

Tank Mixing and Adjuvants

• Adjuvants: A non-ionic surfactant (NIS) or methylated seed oil (MSO) can improve uptake, especially on waxy or stressed weeds

• Tank-mix partners: Atrazine, mesotrione, dicamba, bromoxynil (based on weed spectrum)

• Compatibility check: Always conduct a jar test before mixing with other products