How to Use Diquat Herbicide

A focused, practice-oriented guide to using diquat correctly—limited to use principles and decision factors. No rates, no replicable mixes. Always follow the product label and local regulations.

What Diquat Is and Why It Matters in Use

Diquat is a non-selective, contact herbicide in HRAC Group 22. It disrupts Photosystem I electron transfer, generating reactive oxygen species that scorch leaf tissue. For practical use, this means:

• Performance depends on thorough leaf contact and uniform coverage.

• Mature, lignified, or heavily waxed tissues respond less.

• Activity is primarily at the site of contact; systemic movement within plants is limited.

Where Diquat Fits (Label-Permitted Use Cases)

• Pre-plant burndown: Rapid knockdown of surface weeds and volunteers before planting.

• Directed row-middles/orchard alleys: Target weeds between rows with directional spray; avoid crop contact.

• Non-crop and infrastructure edges: Hard stands, roadsides, and facility perimeters.

• Aquatic weed control: Still or slow-moving waters under water-use restrictions.

• Desiccation/defoliation: Only where specifically allowed on the label for the crop and timing.

Final authority is the registered label in the target market, including crop, site, and timing permissions.

Application Principles (Non-Parametric)

• Coverage first: Aim for even deposition without runoff; fine-to-medium droplets that achieve uniform leaf wetting.

• Target physiology: Actively growing, tender foliage responds best; dusty, aged, or heavily cuticular leaves reduce performance.

• Environment window: Adequate sunlight and low wind enhance outcomes; avoid drift conditions and imminent rainfall.

• Dry-time integrity: Ensure sufficient dry contact time; dew-wet leaves and immediate rainfall can reduce adherence.

Medium and Water Quality Effects

• Soil/organic matter/clay: Strong adsorption reduces bioavailability; minimize off-target contact surfaces.

• Turbidity in water: Suspended solids and algal blooms can consume or sequester actives in aquatic uses; prefer low-turbidity windows.

• pH/hardness/adjuvants: Use only adjuvant types allowed by the label; confirm physical-chemical compatibility with a small jar test.

Tank Mixes and Program Sequencing (Principles Only)

• Purpose: Broaden spectrum, stabilize outcomes, and suppress regrowth.

• Execution: Mix or sequence only where both labels permit; confirm physical compatibility before field use.

• Avoid: Any label-prohibited combinations or sequences; signs of instability such as precipitation, excessive heat, or stratification.

Equipment and Drift Management

• Hardware: Use tips and drift-reduction accessories that balance coverage with off-target control; prioritize directional control in sensitive blocks.

• Cleanout: Follow label procedures for boom, tank, and line sanitation to prevent carryover injury on subsequent jobs.

• Buffers: Maintain label-specified setbacks from sensitive areas, water, and susceptible plantings.

Resistance Stewardship (HRAC 22)

• Rotation: Alternate with different modes of action across the season to avoid single-mechanism dependency.

• Program fit: Pair contact burndown logic with programmatic soil-residual strategies where labels allow; separate roles in time to reduce selection pressure.

• Population view: Monitor grass, broadleaf, and sedge shifts and adjust programs accordingly.

Aquatic Use: Additional Considerations (If Labeled)

• Biomass management: Treating very large infestations at once can depress dissolved oxygen; follow label guidance on sectional or staged treatments.

• Hydrology: Still or low-flow conditions favor contact time and exposure.

• Ecological buffers: Observe protected zones and any local water authority rules.

Safety and Compliance

• Primacy of the label: Follow product label and local regulations at all times.

• PPE and handling: Use protective equipment and handling practices as specified on the label.

• Non-target protection: Manage wind direction, speed, and buffer distances; handle rinsates and remnants per regulations.

Common Failure Modes and Corrections

• Insufficient coverage → Improve droplet spectrum and canopy interception; slow travel speed if necessary.

• Over-mature targets → Shift timing toward actively growing tissue; integrate mechanical disturbance where appropriate and permitted.

• Dust or leaf contaminants → Select a cleaner window or implement pre-wetting strategies only if the label allows.

• Adverse weather window → Re-schedule to align with sunlight, temperature, and wind constraints specified on the label.

Quick Reference Table – Use Case Alignment

FAQs

Can diquat be tank-mixed with other herbicides?
Only if both labels permit and a small-scale compatibility test confirms stability. Respect any label prohibitions.

Why does diquat underperform on woody or highly cuticular tissues?
Its contact mode mainly injures exposed foliage; limited translocation reduces impact on woody structures.

What should be considered for aquatic applications?
Treat under low-flow, low-turbidity conditions and follow label direction on sectional or staged treatments to avoid oxygen depletion.

How do I minimize drift risk near sensitive crops?
Use directional spray hardware, observe buffer zones, monitor wind speed/direction, and avoid temperature inversions—per label guidance.

Is diquat suitable for long-term residual control?
No. It provides rapid contact activity without soil residual. Pair with residual strategies only where labels allow.