Active ingredient
Diquat dibromide
Bipyridylium (photosystem I inhibitor)
A fast contact herbicide, and in home products always a minor partner rather than the headline active — the two we review carry it at 0.073% and 0.12%.
What it does
Burns down whatever the spray wets, visibly and quickly. It is what makes a ready-to-use bottle look like it is working within hours, which is the effect those products are bought for.
What it does not do
It does not translocate. Nothing reaches the root, so a perennial browns off and regrows from the crown — and it leaves nothing in the soil, so next week's seedlings germinate normally. Speed and permanence are opposite properties here.
The label constraint people miss
Both products we review that contain it are sold under names that imply something else. One is branded Roundup and contains no glyphosate at all: EPA Reg. 71995-65 is triclopyr, fluazifop and diquat, and the same registration is also sold as a poison ivy and tough brush killer. If you plan a seeding date around glyphosate guidance and the bottle in your hand is that one, you have planned around the wrong chemistry.
Products we review that contain it
Every product below is here because we opened its label — on EPA's own database or the registrant's — and read Diquat dibromide in the ingredient statement. Registration numbers are on each product's page.
Non-Selective Ready-to-Use Herbicide (wand sprayer)
Roundup Weed & Grass Killer₄ with Pump 'N Go 2 Sprayer (1.33 gal)
★★★★☆ (3.5/5)
The most important thing about this bottle is what is no longer in it: Bayer removed glyphosate from residential Roundup, and this is one of the replacements.
Best for: Spot-killing weeds in driveways, patios and bed edges with no mixing
$22–$28
View on Amazon
Non-Selective Ready-to-Use Herbicide
Spectracide Weed & Grass Killer₂ Ready-to-Use (1 gal)
★★★★☆ (3.8/5)
The cheapest gallon on the shelf, and the ingredient list explains why it must stay off turf: one of the three actives exists specifically to kill grasses.
Best for: Cheap spot treatment of driveways, walkways, gravel and bed edges
$6–$10
View on Amazon
Guides that use Diquat dibromide
Buy for the active, then read the label anyway. Two products with the same active are not interchangeable — concentration, labelled sites and species tolerances all vary, and a three-part registration number means a narrowed label. How to read one in two minutes. Where our page and your container disagree, the container is the legal authority.