Machete (Butachlor): A Pre-Emergent Herbicide for Rice Cultivation

Definition:
Machete is the trade name for Butachlor, a pre-emergent herbicide widely used for controlling annual grasses, sedges, and some broadleaf weeds in paddy rice cultivation. It belongs to the chloroacetanilide class of herbicides and is highly effective when applied before weed emergence.

Chemical Characteristics of Machete (Butachlor):

• Chemical Name: N-(butoxymethyl)-2-chloro-N-(2,6-diethylphenyl)acetamide

• Molecular Formula: C17H26ClNO2

• Molecular Weight: 311.85 g/mol

• Appearance: Pale yellow to brown liquid (technical concentrate).

• Solubility: Sparingly soluble in water; readily soluble in organic solvents.

• Stability: Stable under normal conditions; degrades in alkaline environments.

Mode of Action:

Machete (Butachlor) inhibits protein synthesis and cell division in germinating weed seeds, preventing root and shoot development. It is absorbed mainly by emerging shoots of weeds, resulting in their death before or shortly after emergence.

Uses and Applications:

1. Target Weeds:

   • Controls annual grasses such as Echinochloa crus-galli (barnyard grass).

   • Suppresses sedges (Cyperus spp.) and some broadleaf weeds in flooded rice fields.

2. Crops:

   • Primarily used in transplanted and direct-seeded rice under flooded conditions.

3. Application Timing:

   • Apply pre-emergence (2–5 days after transplanting or sowing) before weed emergence.

Benefits of Machete (Butachlor):

• Highly Effective on Grasses: Provides strong control of grassy weeds in paddy fields.

• Long Residual Activity: Offers weed suppression for 3–4 weeks, reducing early competition.

• Low Phytotoxicity: Safe for rice crops under recommended doses.

• Water-Compatible: Effective under flooded rice field conditions.

Limitations:

• Narrow Weed Spectrum: Limited efficacy on broadleaf weeds; often combined with other herbicides.

• Resistance Risk: Continuous use may lead to resistant weed populations.

• Soil and Water Dependency: Requires a thin water layer for optimal performance.

• Environmental Concerns: May persist in soil and affect aquatic ecosystems if misused.

Recommended Application:

• Dosage: 1.0–1.5 kg active ingredient per hectare.

• Method:

  • Apply as pre-emergence soil incorporation or pre-emergence spray under a shallow water layer.

  • Maintain water level for several days post-application to enhance efficacy.

• Precautions:

  • Do not apply on dry soil without water coverage.

  • Avoid use in non-target areas to prevent contamination.

Storage and Handling:

• Storage: Keep in tightly sealed containers, in a cool, dry place away from food and feed.

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

• Safety: Low acute toxicity to humans, but use protective clothing and avoid inhalation or skin contact.

FAQ on Machete (Butachlor):

Q1: What type of weeds does Machete control?
A1: It primarily controls annual grasses like barnyard grass and suppresses some sedges in rice cultivation.

Q2: When should Machete be applied?
A2: It should be applied as a pre-emergence herbicide, ideally within 2–5 days after transplanting or sowing rice.

Q3: Can it be used for crops other than rice?
A3: No, it is specifically recommended for flooded rice fields and may harm other crops.

Q4: How can resistance be managed?
A4: Rotate Machete with herbicides of different modes of action or use in tank mixes with broad-spectrum herbicides.