Bentazone: A Selective Post-Emergence Herbicide for Broadleaf and Sedges

Technical Introduction

Bentazone (IUPAC: 3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide) is a contact, selective, post-emergence herbicide belonging to the benzothiadiazole chemical family.

It works by inhibiting photosystem II (PSII) in the chloroplasts of susceptible plants, disrupting photosynthetic electron transport. This leads to rapid production of reactive oxygen species (ROS), membrane damage, chlorosis, and necrosis.

• Mode of Action: Photosystem II inhibitor (HRAC Group C3 / WSSA Group 6).

• Systemicity: Non-systemic; acts as a contact herbicide with limited translocation.

• Application Timing: Post-emergence, best when weeds are young and actively growing.

Applications

• Crops:

  • Rice (paddy fields, both upland and flooded)

  • Beans, peas, soybeans

  • Potatoes, maize, peanuts

  • Sunflower, cereals in some regions

• Weeds Controlled:

  • Broadleaf weeds: Amaranthus spp., Chenopodium spp., Polygonum spp., Galium spp.

  • Sedges: Cyperus iria, Cyperus difformis, Fimbristylis spp.

  • Some efficacy on volunteer crops and certain aquatic weeds in rice paddies.

Advantages

• Selective Post-Emergence Action: Safe for many crops, especially legumes and rice.

• Fast-Acting Contact Herbicide: Visible symptoms (leaf burning, chlorosis) appear within days.

• Broad Spectrum: Controls a wide range of annual broadleaf weeds and sedges.

• Flexible Use: Suitable for both upland crops and paddy fields.

• Low Residual Activity: Breaks down quickly in soil, reducing carryover risk for rotational crops.

Specifications (Typical Parameters)

FAQ

Q1: What is Bentazone mainly used for?
A: It is widely used in rice, beans, soybeans, and peanuts to control annual broadleaf weeds and sedges after they emerge.

Q2: Does Bentazone control grasses?
A: No, Bentazone is ineffective on most grasses. It mainly targets broadleaf weeds and sedges.

Q3: How fast does Bentazone act?
A: Symptoms (chlorosis and leaf burn) appear within 1–3 days, with complete weed death in 7–14 days.

Q4: Is Bentazone safe for rotational crops?
A: Yes, it has low soil persistence, so there is minimal risk to rotational crops.

Q5: Can weeds develop resistance to Bentazone?
A: Yes. PSII inhibitor resistance has been documented in some Amaranthus and Chenopodium populations. Integrated weed management is recommended.

Q6: What precautions are needed?
A: Avoid drift to sensitive crops (e.g., tomatoes, cucumbers). Apply under suitable weather conditions, as effectiveness decreases under drought stress.