Dicamba Weed Killers

Dicamba is a selective herbicide that’s been controlling broadleaf weeds since 1967. You’ll rarely find it sold on its own in the UK – instead, it’s typically combined with other active ingredients like 2,4-D, MCPA, and mecoprop to create powerful multi-action lawn weed killers.

If you’ve ever used a professional-grade lawn weed killer, chances are dicamba was one of the active ingredients. It’s particularly valued for tackling weeds that have developed resistance to other herbicides, and for its longer-lasting residual action in the soil.

How Dicamba Works

Dicamba works in a similar way to 2,4-D – it’s a synthetic auxin that mimics natural plant growth hormones. When absorbed through the leaves and roots, dicamba causes uncontrolled cell division and growth in broadleaf plants. The weed essentially grows itself to death as its systems become overwhelmed.

The selectivity comes from how different plants process the chemical. Grasses can metabolise dicamba before it causes significant damage, while broadleaf weeds absorb it throughout their entire system, including the roots. This makes dicamba safe to use on established lawns when applied correctly.

One key difference from 2,4-D is that dicamba persists longer in the soil – up to 14 days of residual activity. This can provide ongoing protection against emerging weeds, but also means you need to be more careful about timing if you plan to reseed or plant in treated areas. For an overview of how different herbicides compare, see our complete guide to weed killers.

Which Weeds Does Dicamba Kill?

Dicamba controls a wide range of broadleaf lawn weeds:

White Clover – One of dicamba’s strengths. Clover patches that resist other treatments often succumb to dicamba-based products.

Creeping Buttercup – The spreading, ground-hugging growth habit makes buttercup tricky, but dicamba reaches the entire root system.

Speedwell and Self-Heal – These low-growing weeds respond well to dicamba, especially when combined with other active ingredients.

Dandelions – Effective control, though often combined with 2,4-D for faster results on established dandelion colonies.

Daisies – Common lawn daisies are readily controlled by dicamba-containing products.

Yarrow and Deadnettle – These tougher weeds are where dicamba really earns its place in multi-ingredient formulations.

What Dicamba Won’t Control: Like other selective lawn herbicides, dicamba doesn’t kill grassy weeds such as couch grass or annual meadow grass. It’s also not suitable for woody weeds like brambles – for those, you need triclopyr-based products.

UK Products Containing Dicamba

You won’t typically find pure dicamba products for home lawn use in the UK. Instead, look for multi-ingredient selective weed killers that list dicamba among their active ingredients:

Four-Way Selective Weed Killers: Products like Dicophar and Enforcer combine 2,4-D, dicamba, MCPA, and mecoprop-P. This four-ingredient approach provides the broadest spectrum of weed control, tackling everything from common dandelions to tough weeds like yarrow and self-heal.

Two-Way Combinations: Some products pair dicamba with mecoprop (like Hygrass-P) for targeted control of specific weed types.

Why Combinations Work Better: Each active ingredient has slightly different strengths. Combining them means fewer weeds can escape treatment, and the different modes of action reduce the risk of weeds developing resistance.

When purchasing lawn weed killer, check the active ingredients list. If dicamba is included alongside 2,4-D or MCPA, you’re getting a professional-grade formulation designed for comprehensive lawn weed control.

How Long Does Dicamba Take to Work?

Dicamba works slightly slower than some other lawn herbicides, but its effects are thorough:

First Signs (7-10 days): Treated weeds begin showing yellowing, curling, and distorted growth as the synthetic auxin disrupts normal development.

Complete Control (2-3 weeks): Most broadleaf weeds will be completely dead within two to three weeks of application.

Residual Activity (up to 14 days): Unlike glyphosate which has no soil activity, dicamba continues working in the soil for up to two weeks, helping prevent new weed seedlings from establishing.

For established perennial weeds with extensive root systems, a follow-up application after 6 weeks may be necessary. Always allow adequate time between treatments to assess results before reapplying.

When and How to Apply Dicamba

Best Timing: Apply dicamba-based products from April to September when weeds are actively growing. The ideal conditions are warm (15-25C), with moist soil and no rain forecast for at least 24 hours.

Application Method: Use a pump sprayer rather than a watering can. Dicamba is volatile and prone to drift, so a sprayer with a coarse nozzle setting helps keep the product where you want it. Never apply on windy days.

Drift Warning: Dicamba can damage nearby plants if it drifts onto them. Be particularly careful near vegetable gardens, flower borders, and neighbouring properties. Ornamental plants, vegetables, and fruit trees are all sensitive to dicamba drift.

New Lawns: Don’t apply dicamba-based products to newly seeded or turfed lawns until they’re at least 6 months established.

Before Reseeding: Because dicamba persists in soil longer than other lawn herbicides, wait at least 6-8 weeks after application before overseeding or repairing bare patches.

Dicamba vs Other Lawn Herbicides

Dicamba vs 2,4-D: Both are selective auxin herbicides, but dicamba handles some tough weeds (like speedwell and yarrow) better than 2,4-D alone. Dicamba also has longer residual soil activity. Many professional products combine both for comprehensive control.

Dicamba vs Glyphosate: Completely different applications. Glyphosate kills everything including grass, while dicamba is selective for lawns. Use glyphosate for paths and total clearance; use dicamba-based products for treating weeds in established turf. For a full breakdown of the most powerful non-selective options, see our guide to the strongest weed killers.

Dicamba vs Triclopyr: Triclopyr specialises in woody weeds like brambles and stumps. Dicamba is for lawn weeds. Different tools for different jobs – if you have both broadleaf lawn weeds and woody brush, you’ll need both types of product.

Safety Considerations

Dicamba requires careful handling:

Protective Equipment: Wear gloves and avoid skin contact when mixing and applying. Wash hands thoroughly after use.

Drift Prevention: Apply only on calm days. Use coarse spray settings to reduce fine droplets that can drift. Keep away from vegetable gardens, ornamental plants, and water features.

Pet and Child Safety: Keep pets and children off treated areas until the spray has completely dried – typically 2-6 hours depending on weather conditions.

Environmental Considerations: Dicamba can affect aquatic organisms. Never apply near ponds, streams, or drainage ditches. Don’t water treated areas for at least 24 hours to prevent runoff.

Frequently Asked Questions

Will dicamba kill my lawn grass?

No. Dicamba is a selective herbicide that targets broadleaf weeds while leaving grass unharmed. However, always follow label rates – excessive application can stress any plant, including turf grass.

How long does dicamba stay in the soil?

Dicamba has residual activity of up to 14 days in soil, and can persist for 30-60 days depending on conditions before fully breaking down. Wait at least 6-8 weeks after application before reseeding treated areas.

Can I use dicamba on a new lawn?

No. Wait until your lawn is at least 6 months established before applying dicamba-based products. Young grass is more vulnerable to herbicide stress and needs time to develop strong roots.

Why is dicamba combined with other herbicides?

Different herbicides control different weeds more effectively. Combining dicamba with 2,4-D, MCPA, and mecoprop creates a product that controls the widest possible range of lawn weeds, reducing the chance of any escaping treatment.

Is dicamba safe for pets?

Once dicamba has dried on the lawn (typically 2-6 hours), treated areas are generally considered safe for pets. For extra caution, keep pets away for 24-48 hours and prevent them from eating treated grass. Always store products securely away from animals and children.

What’s the difference between dicamba and glyphosate?

Glyphosate (found in Roundup) kills all plants including grass – it’s for paths, driveways, and total clearance. Dicamba is selective and only kills broadleaf weeds, making it safe for use on lawns. Never use glyphosate on grass you want to keep.