Oxadiazon: A Pre-Emergence Herbicide for Weed Management

Technical Introduction

Oxadiazon is a pre-emergence, contact-type herbicide belonging to the oxadiazole chemical class. It is primarily used to control annual grasses and broadleaf weeds in rice paddies, turfgrass, ornamental crops, and non-crop areas.

• Mode of Action (MOA): Inhibits protoporphyrinogen oxidase (PPO), an enzyme in chlorophyll and heme biosynthesis. This causes accumulation of toxic intermediates that lead to cell membrane destruction upon light exposure.

• Characteristics:

  • Acts mainly in the soil layer, preventing weed emergence.

  • Provides long-lasting control due to low solubility and persistence in soil.

  • Limited systemic activity (non-translocated).

Applications

• Crops:

  • Rice (paddy fields) – widely used for barnyardgrass and sedges.

  • Turfgrass – for weed-free lawns, golf courses, and sod production.

  • Ornamental plants, fruit orchards, vineyards – safe for established plants.

• Weeds Controlled:

  • Grasses: Echinochloa crus-galli (barnyardgrass), Digitaria spp., Setaria spp.

  • Broadleaves: Amaranthus spp., Chenopodium album, Portulaca oleracea

  • Sedges: Cyperus spp.

• Application Timing:

  • Applied before weed emergence (0–5 days after transplanting in rice, or pre-sowing in turf/ornamentals).

  • Requires moist soil or irrigation for activation.

Advantages

• Strong Pre-Emergence Control: Effective against both grasses and broadleaf weeds.

• Long Residual Effect: Controls weeds for 6–8 weeks.

• Crop Safety: Well tolerated in rice, turf, and ornamentals.

• Low Leaching: Minimal movement in soil due to low water solubility, reducing groundwater contamination risk.

• Resistance Management: Useful in PPO-inhibitor herbicide programs, though rotation is still advised.

Specifications (Typical Parameters)

FAQ

Q1: How does Oxadiazon differ from Butachlor or Pretilachlor in rice?
A: Unlike chloroacetamides (Butachlor, Pretilachlor) that inhibit lipid biosynthesis, Oxadiazon acts via PPO inhibition, making it a good rotation partner to delay resistance.

Q2: Can Oxadiazon be used post-emergence?
A: No, it is strictly a pre-emergence herbicide and ineffective once weeds have emerged.

Q3: How long does it protect rice from weeds?
A: Provides 6–8 weeks of weed control, covering the critical early growth stage of rice.

Q4: Is Oxadiazon safe for turfgrass?
A: Yes, it is widely used in lawns, golf courses, and sod farms to maintain weed-free turf.

Q5: Is there a risk of resistance?
A: PPO-inhibitor resistance has been reported in some regions, so rotation with other herbicide classes is recommended.