Professional Guide: Commonly Used Herbicides for Corn in China

Effective weed control is crucial for successful corn cultivation, as weeds compete for nutrients, water, and sunlight, significantly impacting yield. In China, herbicides are widely used in corn fields to manage weed infestations. This article provides a detailed overview of common corn herbicides, their mechanisms of action, and best application practices to help farmers optimize weed management strategies.

Types of Corn Herbicides

1. Soil-Applied (Pre-Emergence) Herbicides

These herbicides are applied to the soil surface, forming a chemical barrier that prevents weed germination or kills young weeds as they emerge.

Key Examples:

• Acetochlor (乙草胺) – Controls annual grasses (e.g., barnyardgrass, crabgrass) and some broadleaf weeds.

• Atrazine (莠去津) – Effective against broadleaf weeds and some grasses; residual activity but may affect subsequent crops.

• Metolachlor / S-Metolachlor (异丙甲草胺 / 精异丙甲草胺) – Improved versions of acetochlor with better efficacy and safety.

• 2,4-D (2甲4氯) – Primarily targets broadleaf weeds but may lose effectiveness as weeds mature.

Mechanism:

• Absorbed by weed roots or shoots, inhibiting cell division and protein synthesis.

• Best applied before weed emergence under adequate soil moisture.

2. Post-Emergence (Foliar) Herbicides

These are applied after weeds have emerged, targeting actively growing plants.

(A) Selective Herbicides

Kill specific weeds without harming corn.

Key Examples:

• Nicosulfuron (烟嘧磺隆) – Controls grasses (e.g., foxtail, crabgrass) and some broadleaf weeds.

• Mesotrione (硝磺草酮, Methylsulfentrazone) – Effective against broadleaf weeds and some grasses; causes bleaching of leaves.

• Bromoxynil (溴苯腈) – Fast-acting contact herbicide for broadleaf weeds.

• Fluroxypyr (氯氟吡氧乙酸) – Targets tough broadleaf weeds like bindweed and thistles.

Mechanism:

• Absorbed through leaves and translocated to growing points.

• Disrupts photosynthesis or amino acid synthesis, leading to weed death.

(B) Non-Selective (Broad-Spectrum) Herbicides

Kill all green vegetation; used in non-crop areas or before planting.

Key Examples:

• Glyphosate (草甘膦) – Systemic herbicide, kills roots and shoots.

• Paraquat (百草枯) – Fast-acting contact herbicide (banned in many countries due to toxicity).

Mechanism:

• Glyphosate inhibits EPSP synthase, disrupting plant growth.

• Paraquat destroys cell membranes via oxidative stress.

Application Methods & Best Practices

1. Acetochlor (乙草胺) – Pre-Emergence Use

• Target Weeds: Crabgrass, foxtail, goosegrass, and some broadleaf weeds.

• Mechanism: Inhibits root and shoot growth in germinating weeds.

• Dosage: Apply before planting or immediately after, ensuring soil moisture for activation.

• Note: Upgraded versions (metolachlor/S-metolachlor) offer better crop safety.

2. 2,4-D Butylate (2,4-D丁酯) – Broadleaf Weed Control

• Target Weeds: Pigweed, lambsquarters, bindweed, and other broadleaf species.

• Mechanism: Mimics plant hormones, causing uncontrolled growth and death.

• Dosage:

  • Pre-emergence: 30-50 mL/mu (72% formulation).

  • Post-emergence (corn at 4-5 leaf stage): 20-30 mL/mu.

• Caution: Highly volatile; avoid drift to sensitive crops (e.g., soybeans, cotton).

3. Nicosulfuron (烟嘧磺隆) – Post-Emergence Grass & Broadleaf Control

• Target Weeds: Crabgrass, barnyardgrass, pigweed, and nightshade.

• Mechanism: Inhibits ALS enzyme, stopping amino acid synthesis.

• Dosage: 40-60 mL/mu (4% formulation) at corn’s 3-5 leaf stage.

• Caution:

  • Avoid use on sweet corn, popcorn, or seed corn.

  • Do not mix with organophosphate insecticides.

4. Atrazine (莠去津) – Dual Pre- & Post-Emergence Use

• Target Weeds: Broadleaf weeds (better) and some grasses.

• Mechanism: Blocks photosynthesis by disrupting electron transport.

• Dosage:

  • Pre-emergence: 175-200 mL/mu.

  • Post-emergence: 125-150 mL/mu.

• Caution: Long soil residual; may harm subsequent crops (rotate carefully).

5. Mesotrione (硝磺草酮) – Broad-Spectrum Post-Emergence Control

• Target Weeds: Pigweed, lambsquarters, velvetleaf, and grasses.

• Mechanism: Inhibits HPPD enzyme, causing leaf bleaching.

• Dosage:

  • Spring corn: 80-120 mL/mu (5% formulation).

  • Summer corn: 60-100 mL/mu.

• Advantage: Safe for corn even after 5-leaf stage.

Key Considerations for Herbicide Use

1. Timing is Critical

   • Pre-emergence herbicides must be applied before weed germination.

   • Post-emergence herbicides work best on young weeds (2-4 leaf stage).

2. Weather & Soil Conditions

   • Avoid application under drought or heavy rain.

   • Soil moisture enhances pre-emergence herbicide activation.

3. Resistance Management

   • Rotate herbicide modes of action to prevent weed resistance.

   • Use tank mixes (e.g., atrazine + mesotrione) for broader control.

4. Safety Precautions

   • Follow label instructions to avoid crop injury.

   • Clean sprayers thoroughly after using volatile herbicides like 2,4-D.

Conclusion

Selecting the right herbicide—whether soil-applied (pre-emergence) or foliar-applied (post-emergence)—is essential for effective weed management in corn fields. Farmers should consider weed spectrum, crop safety, and environmental factors when choosing herbicides. By following best application practices and resistance management strategies, Chinese corn growers can maximize yields while minimizing herbicide-related risks.

For optimal results, consult local agricultural extension services for region-specific recommendations.