Diclofop-methyl: A Selective Post-Emergence Herbicide

Technical Introduction

Diclofop-methyl (IUPAC: methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoate) is a selective, post-emergence herbicide from the aryloxyphenoxypropionate (AOPP) group, also known as the “FOP” herbicides.

It is widely used for grass weed control in cereals, oilseeds, and turf. Once absorbed by leaves, the ester is hydrolyzed into its active acid (diclofop), which inhibits acetyl-CoA carboxylase (ACCase) — an essential enzyme in lipid biosynthesis. This leads to rapid growth inhibition and death of grassy weeds.

• Mode of Action: ACCase inhibitor (HRAC Group A).

• Systemicity: Absorbed by leaves, translocated to meristematic tissues.

• Selectivity: Safe for broadleaf crops and wheat/barley at recommended rates.

Applications

• Cereal Crops:

  • Wheat, barley, rye, oats (selective control of annual grass weeds).

• Oilseeds:

  • Canola, soybeans, sunflower (selective control of grassy weeds).

• Weeds Controlled:

  • Annual grasses including:

    • Avena fatua (wild oat)

    • Lolium rigidum (ryegrass)

    • Phalaris spp. (canarygrass)

    • Setaria spp. (foxtail grasses)

    • Echinochloa crus-galli (barnyardgrass)

• Non-crop Use:

  • Turf management, industrial areas.

Advantages

• Effective Grass Control: Specifically targets annual grassy weeds while sparing broadleaf crops.

• Post-Emergence Flexibility: Can be applied after crop and weed emergence.

• Fast Action: Visible symptoms (leaf chlorosis, necrosis) within days.

• Crop Safety: Selective at recommended dosages.

• Compatible in Tank Mixes: Can be combined with broadleaf herbicides to broaden spectrum.

Specifications (Typical Parameters)

FAQ

Q1: What crops is Diclofop-methyl used on?
A: Mainly in cereals (wheat, barley, rye, oats) and broadleaf crops (soybean, canola, sunflower) for grass weed control.

Q2: Which weeds does Diclofop-methyl control best?
A: Excellent against wild oats, ryegrass, foxtail grasses, barnyardgrass, and canarygrass.

Q3: Is Diclofop-methyl systemic or contact?
A: It is a systemic herbicide, absorbed through leaves and translocated to growth points.

Q4: Can Diclofop-methyl be mixed with other herbicides?
A: Yes, often tank-mixed with broadleaf herbicides (e.g., MCPA, 2,4-D) to expand the weed spectrum.

Q5: Is resistance an issue with Diclofop-methyl?
A: Yes. Overuse has led to widespread ACCase inhibitor resistance, especially in wild oats and ryegrass. Rotation with other herbicide modes of action is strongly recommended.

Q6: What is the typical dose?
A: Usually 0.5–1.0 kg a.i./ha, depending on crop, weed species, and growth stage.