Mesosulfuron-methyl: A Selective Post-Emergent Herbicide for Grass Weed Control

Definition:
Mesosulfuron-methyl is a selective, post-emergent herbicide used primarily in cereal crops such as wheat and barley to control a broad range of grass weeds and some broadleaf weeds. It belongs to the sulfonylurea class of herbicides and is widely recognized for its low application rate and high efficiency.

Chemical Characteristics of Mesosulfuron-methyl:

• Chemical Name: Methyl 2-[[[[(4,6-dimethoxypyrimidin-2-yl)amino]carbonyl]amino]sulfonyl]-4-(methanesulfonylmethyl)benzoate

• Molecular Formula: C₁₇H₂₁N₅O₉S₂

• Molecular Weight: 503.5 g/mol

• Appearance: Off-white to beige crystalline solid (technical grade).

• Solubility: Low solubility in water; soluble in organic solvents.

• Stability: Stable under normal conditions but degrades in acidic or alkaline environments.

Mode of Action:

Mesosulfuron-methyl inhibits the acetolactate synthase (ALS) enzyme, which is essential for the synthesis of branched-chain amino acids in plants. This inhibition stops cell division and weed growth, leading to plant death.

Uses and Applications:

1. Target Weeds:

   • Controls grass weeds such as wild oats (Avena fatua), blackgrass (Alopecurus myosuroides), ryegrass (Lolium spp.), and brome species (Bromus spp.).

   • Also suppresses certain broadleaf weeds in cereals.

2. Crops:

   • Widely used in winter wheat, durum wheat, and barley.

3. Timing:

   • Applied post-emergence when weeds are in the early growth stage (2–4 leaf stage) for best results.

Benefits of Mesosulfuron-methyl:

• Highly Effective: Provides strong control of grass weeds in cereal crops.

• Low Use Rate: Effective at very low dosages, reducing chemical load in the field.

• Selective Action: Safe for cereal crops when applied as directed.

• Resistance Management: Useful for managing grass weed resistance when rotated with herbicides of different modes of action.

Limitations:

• ALS Resistance Risk: Overuse can lead to resistance in grass weed populations.

• Narrow Spectrum: Primarily effective on grasses; less activity on broadleaf weeds.

• Soil Restrictions: Works best in well-prepared fields; poor efficacy on stressed weeds.

Recommended Application:

• Dosage: 10–15 g active ingredient per hectare, often combined with a safener (e.g., iodosulfuron) or adjuvant for enhanced crop safety.

• Method: Foliar spray with good coverage.

• Precautions:

  • Rotate with herbicides of different modes of action to avoid resistance.

  • Avoid overlapping spray and drift onto non-target crops.

Storage and Handling:

• Storage: Keep in original packaging, tightly sealed, in a cool, dry place.

• Shelf Life: 2–3 years under recommended conditions.

• Safety: Avoid contamination of water bodies and wear protective equipment during handling.

FAQ on Mesosulfuron-methyl:

Q1: What crops is Mesosulfuron-methyl safe for?
A1: It is primarily used in wheat and barley and is safe for these crops when applied correctly.

Q2: Can it be tank-mixed with other herbicides?
A2: Yes, it is often mixed with broadleaf herbicides or adjuvants to widen weed control.

Q3: Does it control perennial grasses?
A3: No, it is most effective against annual grass weeds and some early-stage broadleaf weeds.

Q4: How can resistance be managed?
A4: Rotate with herbicides having different modes of action and avoid repeated use on the same field.