Glyphosate (sold under the trade name Roundup) is one of the most effective, widely used, and safest herbicides in the U.S.

But beware—always read the label. Ready-to-use herbicide formulations of glyphosate often contain diquat, a quick acting nonselective herbicide that may be harmful or fatal to humans if swallowed, inhaled, or absorbed through the skin. Skin absorption is particularly dangerous. In animal testing, prolonged exposure to diquat was shown to cause cataracts. It can also poison some species of fish and harm waterfowl.

The theory behind adding diquat to glyphosate is that it “makes the glyphosate work faster.” Ironically, a 2008 Study in Weed Technology showed that while the glyphosate-diquat formulation appeared to more quickly injure greenhouse plants, glyphosate alone had better long-term plant growth suppression.

I think I will stick with good old glyphosate—it’s been around since 1974.

That said, all herbicides carry risks—some studies have linked prolonged glyphosate exposure to non-Hodgkin lymphoma. Always read the label instructions and use herbicides with care. I use them only as a last resort. Avoid windy days, wear skin protection, goggles, a safety mask, and foot covering. And be careful with pets—they shouldn’t walk in any herbicide that hasn’t fully dried. Exposure to wet glyphosate can cause pets to drool, vomit, have diarrhea, lose their appetite, and seem sleepy.

It’s cold now, but gardeners will be battling weeds again before we know it!

— Marty Fisher, EMGV

Sources and more information:

http://pmep.cce.cornell.edu/profiles/extoxnet/dienochlor-glyphosate/diquat-ext.html

https://www.cdpr.ca.gov/docs/risk/rcd/diquat.pdf

http://npic.orst.edu/factsheets/glyphogen.html

http://www.bioone.org/doi/pdf/10.1614/WT-07-181.1?download=true