Note: this is an old post that I thought would be useful on Earth Day. You are not having déjà vu!
The recipe for success: read the ingredient list of whatever you are planning to use. The problem is that sometimes the manufacturers “forget” to list an ingredient or two and then you need to read between the lines.
First, let me tell you that herbicides are based on the same principle as antibiotics: they have to be selective, i.e. kill the baddie without harming the goodie, For antibiotics (and antifungals) the baddie is the microbe, and we humans are the goodies. For herbicides, the goodie is your pretty garden plant, or the crop, and the baddie is the weed, which is, by definition, whatever you don’t want growing. To achieve selectivity you have to target a biochemical step that the host (or crop) doesn’t have or is not affected as badly.
This principle is beautifully covered by a herbicide called glyphosate: it inhibits an enzyme, 5-enolpyruvylshikimate-3-phosphate synthase. We humans don’t have the enzyme so we should be OK.
Monsanto also developed a soy plant that is “immune” to this herbicide. What could be better for Monsanto? It sells a herbicide, and a seeds that will sprout into soy plant immune to the herbicide (normal soy, like every other plant, is sensitive to glyphosate), making double the money by selling the pair.
In the garden, the herbicide Roundup is a big seller because it kills the weeds in hours! This is instant gratification for the home gardener: spray the weed and see it die almost in front of your eyes. Even an antibiotic that fights very fast growing bacteria will take a day until it makes you feel better.
My grandson Joseph wanted to do a project about this best seller, he wanted to show that you did not have to buy a herbicide that is likely to harm the environment. You could use vinegar!
Here I am, the plant physiologist/biochemist explaining him that glyphosate is OK for humans because we don’t have the enzyme that glyphosate is inhibiting. We don’t make the amino acids that the enzyme is involved in synthesizing. How could vinegar do that fancy job?
Except that my grandson was right and I was wrong. As soon as I let my brain work rather than trusting the label, the plant physiologist in me realized that inhibiting an enzyme that affects protein synthesis should take a while to work. Young tissue should be affected more or less immediately, but not in hours, and the whole plant should no be wilting so quickly! Then I noticed the label: there is something else in there but it is disguised under the “fast act technology”. You might be tempted to imagine little bubbles that target the leaves and shoots and deliver the herbicide so quickly that the inhibition of protein synthesis is instant and the plants wilt within our. No, that’s the kind of cartoon that companies use to sell us stuff, but cartoons don’t represent reality.
What is that “fast acting technology”? Another chemical, and one that has nothing to do with glyphosate. That “phantom” chemical is not identified on the label (thanks to lobbyists in Congress) and we should assume that it has not been tested on humans for safety.
In short: The “instant satisfaction” ingredient is NOT glyphosate, so all of the great safety talk about Roundup is actually pure deflection. What’s this chemical? I don’t know as it is not listed, but there are a number of chemicals that can disrupt plant cell membranes (and human cell membranes as well). As soon as I realized what was going on I started wearing gloves any time I was handling Roundup at any concentration.
And, yes, my grandson was right: vinegar will achieve the wilting. It may take a bit longer or, if you don’t want to wait, use a higher concentration of acetic acid. Cheaper, and safer for us and the environment.