Cycloxydim: A Selective Post-Emergent Grass Herbicide

Definition:
Cycloxydim is a systemic, selective post-emergent herbicide from the cyclohexanedione (DIM) class. It is primarily used to control annual and perennial grass weeds in broadleaf crops, offering effective control without harming non-grass crops.

Chemical Characteristics of Cycloxydim:

• Chemical Name: (±)-2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one

• Molecular Formula: C₁₇H₂₇NO₃S

• Molecular Weight: 325.47 g/mol

• Appearance: Yellowish liquid (in formulations) or crystalline solid (pure).

• Solubility: Low solubility in water; soluble in organic solvents.

• Stability: Stable under normal conditions; hydrolyzes in strong alkaline environments.

Mode of Action:

Cycloxydim inhibits acetyl-CoA carboxylase (ACCase), an enzyme vital for fatty acid synthesis in grasses. This inhibition disrupts lipid formation in grass weeds, leading to chlorosis, stunted growth, and death, while broadleaf crops remain unaffected due to ACCase enzyme insensitivity.

Uses and Applications:

1. Target Weeds:

   • Annual grasses: Wild oats (Avena fatua), foxtail (Setaria spp.), barnyardgrass (Echinochloa spp.).

   • Perennial grasses: Johnson grass (Sorghum halepense), Bermuda grass (Cynodon dactylon).

2. Crops:

   • Broadleaf crops such as soybean, sugar beet, canola, sunflower, vegetables, and fruit crops.

3. Timing:

   • Applied post-emergence when grass weeds are in active growth stages (2–6 leaf).

Benefits of Cycloxydim:

• High Selectivity: Safe on broadleaf crops, even at recommended rates.

• Broad Grass Spectrum: Effective against annual and perennial grass weeds.

• Systemic Action: Translocates rapidly to weed meristems for thorough control.

• Flexible Tank Mixing: Can be combined with broadleaf herbicides for complete weed management.

Limitations:

• No Broadleaf Weed Control: Ineffective on non-grass species.

• No Soil Residual Activity: Only affects emerged grass weeds.

• Resistance Risk: Overuse can select for ACCase inhibitor-resistant grasses.

Recommended Application:

• Dosage: 100–250 g active ingredient per hectare, depending on target weed species.

• Method: Foliar spray with sufficient coverage and adjuvant (e.g., crop oil concentrate) for absorption.

• Precautions:

  • Apply when weeds are small and actively growing.

  • Avoid drift onto grass crops (e.g., maize, cereals).

  • Rotate with other herbicide modes of action to prevent resistance.

Storage and Handling:

• Storage: Keep in original containers in a cool, dry, and ventilated area.

• Shelf Life: 2–3 years when stored properly.

• Safety: Use PPE during handling; toxic to aquatic organisms.

FAQ on Cycloxydim:

Q1: What weeds does Cycloxydim control?
A1: It targets annual and perennial grasses like wild oats, foxtail, and Johnson grass but does not affect broadleaf weeds.

Q2: Is Cycloxydim safe for broadleaf crops?
A2: Yes, it is designed to selectively control grass weeds without damaging broadleaf crops.

Q3: Does it provide residual weed control?
A3: No, it only controls actively growing grasses present at application time.

Q4: How can resistance be managed?
A4: Alternate with herbicides of different modes of action and include cultural weed control practices.