Benfluralin: A Pre-Emergent Dinitroaniline Herbicide

Definition:
Benfluralin is a selective, pre-emergent herbicide from the dinitroaniline (DNA) class. It is widely used to control annual grasses and certain broadleaf weeds in crops such as soybeans, sunflowers, ornamentals, and turf. Benfluralin inhibits weed germination and early seedling growth by affecting cell division.

Chemical Characteristics of Benfluralin:

• Chemical Name: N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)aniline

• Molecular Formula: C₁₃H₁₆F₃N₃O₄

• Molecular Weight: 335.3 g/mol

• Appearance: Yellow-orange crystalline solid.

• Solubility: Very low water solubility (<1 mg/L); soluble in organic solvents.

• Stability: Stable under normal conditions but prone to photodegradation when exposed to sunlight.

Mode of Action:

Benfluralin disrupts microtubule formation by binding to tubulin proteins, preventing proper cell division (mitosis) in germinating weed seeds. This leads to abnormal root and shoot development, ultimately killing the weed seedlings before emergence.

Uses and Applications:

1. Target Weeds:

   • Annual grasses: foxtail (Setaria spp.), barnyardgrass (Echinochloa spp.), crabgrass (Digitaria spp.).

   • Certain small-seeded broadleaf weeds such as pigweed (Amaranthus spp.).

2. Crops and Areas of Use:

   • Field crops: Soybeans, sunflowers, peanuts, and cotton.

   • Horticulture: Ornamentals and nursery crops.

   • Turf and lawns: Pre-emergent control of grassy weeds.

3. Application Timing:

   • Pre-emergence: Applied to soil before weed germination; requires incorporation by mechanical means or irrigation to prevent photodegradation.

Benefits of Benfluralin:

• Effective Pre-Emergent Control: Prevents weed establishment early in the season.

• Low Water Solubility: Minimizes leaching risk and groundwater contamination.

• Selectivity: Safe for labeled crops when applied at recommended rates.

• Residual Activity: Provides extended weed control when incorporated properly.

Limitations:

• No Post-Emergent Activity: Ineffective on emerged weeds.

• Soil Incorporation Required: Photodegradation can reduce efficacy if not incorporated promptly.

• Resistance Development: Overuse can lead to dinitroaniline-resistant grass species.

Recommended Application:

• Dosage: Typically 0.5–2.0 kg active ingredient per hectare, depending on soil type and weed spectrum.

• Method: Apply to soil surface and mechanically incorporate or irrigate within 24 hours.

• Precautions:

  • Avoid direct contact with crop seeds during planting to prevent injury.

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

Storage and Handling:

• Storage: Store in tightly sealed containers in a cool, dry location away from direct sunlight.

• Shelf Life: Stable for 2–3 years under proper conditions.

• Safety: Use protective clothing and avoid inhalation or skin contact; toxic to aquatic organisms.

FAQ on Benfluralin:

Q1: What is Benfluralin used for?
A1: It is used pre-emergence to control annual grasses and some broadleaf weeds in crops, ornamentals, and turf.

Q2: How is Benfluralin applied?
A2: It must be soil-applied and incorporated mechanically or through irrigation before weed germination.

Q3: Does Benfluralin have residual activity?
A3: Yes, it provides extended pre-emergent control when properly incorporated.

Q4: Can weeds develop resistance to Benfluralin?
A4: Yes, continuous use can result in resistant grass weed populations; herbicide rotation is recommended.