Yes, there is a non-glyphosate burndown herbicide that's exempt from EPA registration

It's labeled "Weed Slayer." It's systemic. It's based on a natural herbal source, and it's potent. But it's a bit pricey for non-selective herbicide use to terminate big acreages of cover crops. Research agronomist Jim Porterfield offers some insights.

July 17, 2020 — Jim Porterfield's research farm in Illinois comes up with a surprise almost every season. This summer, one of his field trials checked out the effects of a weedkiller with the active ingredient Eugenol, known more commonly as clove oil. 

Jim demonstrated that Weed Slayer's 3% Eugenol blend, plus an adjuvant, fried broadleaves and grasses. But when sprayed on weeds in corn rows, the systemic effect stunted corn. Jim's advice: Don't spray close to growing corn, where weed roots and corn roots mingle. Applied as a foliar, Eugenol toxicity is highly systemic. It moves into root systems and apparently gets picked up by adjacent crop roots.

We've experimented with a wide array of burndown chemicals, but none were systemic. Only the sprayed leaves were killed, which required a thorough coverage of weeds. A 20% acetic acid is one of the most common "natural" weedkillers sold in USA retail stores. We learned that WakeUP Summer makes acetic acid more effective because of more uniform leave coverage, but acetic acid still doesn't translocate to kill roots even with WakeUP in solution. 

The photo below makes it clear how Weed Slayer impacts adjacent corn. The tall stalks were not close to the weedkiller, which was foliar-applied carefully on weeds in the rows. The short stalks in the photo were next to grasses sprayed with Weed Slayer. 

Economics: The recommended application rate of Weed Slayer and its biological companion product, Agro Gold, is a quart of each product (two quarts total) in 20 gallons of water. (Agro Gold is a biological product which enhances the Eugenol effect of Weed Slayer.) The cost of the combination product on Amazon.com is $70 for eight quarts. Thus if you spray 20 gallons of solution per acre with two quarts of the blended products, your cost per acre is about $17.50. That's significantly higher per acre than glyphosate or gramoxone, but Weed Slayer and Agro Gold are considered organically approved and exempt from EPA registration because ingredients are natural. 

Jim Porterfield added WakeUP Summer to the combination of Weed Slayer and Agro Gold to intensify absorption and translocation. You can read Jim's detailed plot summary by downloading his PDF report

For detailed application instructions of Weed Slayer, here's a link to Adaman Ag, a diverse distributor of environmentally friendly ag products, primarily in California. This link opens a page with additional links to the product labels and videos of spray results.

 

Shorter cornstalks show reduced growth from apparent allelopathic effect of Weed Slayer foliar-applied on adjacent weeds.

 

Since 2015 we've been cooperating in field testing of another burndown herbicide developed in Australia and tested in several countries including the USA. The company is Contact Organics. The American partner in this development work is Howard Vlieger, farmer-entrepeneur at Maurice, Iowa. The company's strategy was to gain registry in Australia first, then register for a series of EPA approvals in the United States. The active ingredient in their products is a specific formulation of acetic acid. The firm addresses three markets with these three trademarked labels:

HomeSafe is for home use around the garden and yard.

LocalSafe is intended for municipal, sports ground and hobby farm weed control.

FarmSafe is for broadacre farming use, such as terminating cover crops. The firm is still working its way through EPA's approval process, while its readily available in Australia.

An adjuvant developed by Contact Organics is blended by the applicator as a two-part product, to make the acetic acid more effective.

In our early work with Howard Vlieger, we demonstrated that WakeUP Summer intensified the weed-killing impact of acetic acid. However, WakeUP is not registered as an organic product, which Contact Organics wanted. 

Contact Organics Founding Director and Inventor, William Briggs, developed a proprietary adjuvant solution which makes their acetic acid more effective and qualifies as organic in Australia. A company media release offers more background on this product. 

Meanwhile, Howard Vlieger is shepherding registration application with EPA and conducting demonstrations around the USA.

The good news in these two products: Their environmentally safe nature points the way to a new, non-residual potential for similar herbicides.