The angst about pesticide regulation reminds me of an longtime organic vegetable farmer who moved into Northwest Arkansas, originally from California. He got up and left California after being told by a state regulatory agency that putting beer out in aluminum trays at night to kill slugs was "illegal".
It reminds me of the recent situation where a (Missouri) Department of Agriculture employee confronted a magician for pulling a rabbit out of his hat, suggesting that he wasn't keeping livestock properly, or lacked a license or something like that, a true story which you can find on Google News.
Anyways, Chris, yes there is a series of research reports from land-grant universities and trade magazine articles that demonstrate the efficacy of "green chemistry" herbicides for controlling vegetation; i.e., acetic acid, citric acid, thyme oil, etc.; often with pictures and percentage kill; with variable results.
My rapid assessment field trials showed that 20% acetic acid was very effective (80-90%) on many broadleaf seedlings while only somewhat effective on grassy plants (60-70%) like bermudagrass, but when repeated in 4-7days the kill on grassy plants zoomed up (80-90%). The concept behind this is that grassy plants arise from a growing point below the ground so you really only get a contact effect vs a systemic effect, and thus repeated treatments will be required for longer term control. The other concept is that you don't always need to kill a weed, you only need to suppress it. The other concept is that you're mainly looking at spot treatment in non-cropland areas (edges of field, irrigation pumps, pathways) because it is really expensive to apply this materials at full strength vs products applied in diluted forms. And, yes, it is caustic so caution and safety is warranted during application. I don't have enough experience with the labeled products to say much, but that's where growers would need to put their focus and abide with pesticide regulations.
Likewise, for poison ivy, certain mixtures of 20% acetic acid and citric acid at various percentages was pretty effective while others were less effective. Some of the pictures I obtained of leafy burn would get weed scientists excited. But again, it was a contact treatment vs a systemic treatment and required repeated applications for a big set back.
The bottom line is that "green chemistry herbicides" have some uses, but are really no substitute for synthetic herbicides in terms of scale of application, multiple uses, and effectiveness. On the other hand, in production systems that askew herbicides, such as organic crop/vegetable/fruit production, you can achieve good production without herbicides in the first place. There are many little hammers and technologies in an integrated production system that achieve weed control and/or weed suppression.www.Free-RangePoultry.com