Before my paralyzation forced me to retire, I spent twelve years in the advertising agency business focusing on agricultural clients. I moved to St. Louis and one of my clients was Monsanto, specifically Roundup in the Southern and Western US markets. This was from 1993-1996.
My key objective was to speed up the adoption of no-till farming methods n the South where the practice was not as embraced as in the Midwest.
Al Gore has been criticized for his characterization of Roundup in Earth in the Balance: Ecology and The Human Spirit (2006) as a safer herbicide because its mode of action affects just one enzyme. He went on to advocate that it should serve as a model for future product development.
In How to Eradicate Invasive Plants (2013), Teri Dunn Chace does a great job in explaining the unique mode of action of the product:
“Glyphosate by itself is not a poison. It works by interfering with a plant’s ability to manufacture key amino acids, thus thwarting protein production. This interference, essentially, makes it impossible for the plant to photosynthesize and go on living.”
From my internal Monsanto education, glyphosate actually inhibits the action of just one key enzyme. This is why it’s been so easy for Monsanto to develop Roundup Ready crop seed that is resistant to applications of Roundup. So growers have been able to apply cheap, generically priced Roundup to kill the majority of weeds as opposed to more expensive pre-emergent that are more hostile to the environment. But recent scientific papers have found glyphosate to be associated with birth defects and is lethal to amphibians. Glyphosate should not be used near water sources or water gardens.
One of the benefits of Roundup is it is systemic and so the chemical is translocated through the entire plant killing roots and all. This makes Roundup so effectives on mature weeds with heavy root systems and weeds with long taproots. But this action can take up to seven to ten days, so it’s different than slash and burn weed killers that destroy only the tissue that is directly exposed to the product.
I was surprised when Dunn Chase suggested and endorsed the off-label, paint brush method of application. She says you can “mitigate environmental harm by painting on, rather than broad case spraying the product, which is more diffuse and less targeted. In some cases, you may have to use a higher concentration for stem painting to be effective.”
I have painted Roundup on the the leaves and stems of weeds that are found in the midst of a desirable planting with much success, I have taken advantage of the systemic action and have carefully painted the foliage with a hobby-like paintbrush. This method, though controversial, is very effective. Some believe there are significant health risks in being in such close contact of the product.
From my personal experience, there are two major weeds that Roundup is not effective on. Both nutgrass and henbit are not phased by glyphosate.
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