Weeds Don't Resist. They Adapt.

Voltaire said that “History never repeats itself; man always does.”

George Santayana said "Those who cannot remember the past are condemned to repeat it."

In all facets of life, we often fail to learn from the past.

Even in weed management, we fail to learn from the past.

In his book “Same as Ever,” Morgan Housel highlights that some things never change: "people falling for greed and fear; people persuaded by risk, jealousy, and tribal affiliations; overconfidence and shortsightedness; people seeking the secret to a happy life and trying to find certainty when none exists."

I’d add one more to his list: People succumbing to the seductiveness of Silver Bullets — because we love a great narrative and an easy button.

Many of us fall for the seductiveness of Silver Bullets — whether it is the next “get rich quick” scheme, or weight loss formula (though, GLP-1’s may have me here).

We also fall for them in weed management.

Failure to learn from the past and following our affinity for silver bullets leads to many problems in weed management.

Two weeks ago, I highlighted the sneaky ways weeds could adapt to overcome alternative weed control methods, like laser or mechanical weeding.

This week, I read another comment from a VC surrounding weeds being unable to adapt to mechanical weeding mechanisms (emphasis mine):

The bolded statement is objectively false. Weeds can, and have, adapted to mechanical control methods through phenological approaches (eg: changes in time to seed set), morphological mechanisms (eg: prostrate grow habit) and spectrum shifts on a field basis to rhizome-dominant species, as a few examples.

This is not the first, nor the last time someone will say something to that effect about new methods of controlling weeds.

But we always underestimate how clever Mother Nature can be.

In fact, at one point, the makers of glyphosate made similar claims — and now glyphosate has documented resistance from ~60 weed species worldwide (and growing), with about 20 of those in North America.

Glyphosate was first commercialized as Roundup in 1974.

It worked by inhibiting an enzyme (EPSPS) in the shikimate pathway that plants need to make essential amino acids, but that animals lack entirely, which gave it a sound toxicology profile plus had a broad-spectrum, systemic, non-selective control. It also bound tightly to soil and broke down microbially, so residual carryover was minimal and crop rotation optionality stayed wide open. It was considered a once-in-a-lifetime molecule.

On top, the conventional wisdom was that resistance would never become a serious issue rested on a few specific assumptions: EPSPS is highly conserved with little room for mutation that wouldn't carry a fitness penalty, and no natural analog existed in the environment to pre-condition weed populations.

More than two decades passed without confirmed field resistance.

In 1997, four Monsanto scientists (Laura Bradshaw, Stephen Padgette, Steven Kimball, Barbara Wells) published “Perspectives on Glyphosate Resistance.” The following statements were made in the paper: