Bentazone

What It Is

Bentazone is a post-emergence herbicide used to control broadleaf weeds and some sedges. It belongs to the benzothiadiazole chemical family and acts as a contact herbicide, meaning it only kills the plant tissue it touches rather than being translocated throughout the plant.

Mode of Action

• Target site: Photosystem II inhibitor.
• Blocks electron transport in photosynthesis, causing rapid chlorosis and necrosis of treated leaves.
• Classified by the Herbicide Resistance Action Committee (HRAC) as Group C3.

Because it is a contact herbicide, full spray coverage is essential for effective weed control.

Applications

• Agriculture:
  • Widely used in soybeans, dry beans, and peas.
  • Selective in legumes due to crop tolerance mechanisms.
• Horticulture:
  • Applied in some vegetable crops (e.g., onions, potatoes).
• Turf & Landscape:
  • Occasionally used for weed management in turfgrass, though less common than other herbicides.

Environmental Considerations

• Mobility: Bentazone is water-soluble and mobile in soil, making it prone to leaching into groundwater.
• Persistence: Moderate half-life; can be detected in surface and groundwater long after application.
• Regulation:
  • Approved in many countries but under strict monitoring.
  • The EU has imposed restrictions due to water contamination risks.

Producers

• Originally developed by BASF.
• Still manufactured and sold by multiple generic agrochemical companies globally.

Why It Matters

Bentazone remains an important selective herbicide for legumes, offering a mode of action that helps diversify weed control programs. However, its environmental profile — particularly water contamination — makes it a focus of regulatory scrutiny.

Outlook

• Use is likely to decline in Europe due to stricter water protection policies.
• Could remain relevant in North and South America, where legumes are major crops and herbicide resistance management is critical.
• Alternative chemistry and integrated weed management will be needed as bentazone faces tighter restrictions.

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