Crops Insights

Perspective: Commodity enemy #1 is pest resistance


A group gathers nervously in a room, antsy about a potential diagnosis.

The victim, the consummate trooper, girds themself for the worst.

“Just give it to me straight doc.”

Matter of factly — and with little concern for bedside manner — the doctor delivers the sobering news.

“We’re sorry, it’s … resistance.”

“What are my options?”

All this drama for an anticlimactic payoff? Hardly! It’s the diagnosis all farmers dread. And historically, the prognosis hasn’t been good.

But what is resistance, and why should anyone care?

Companies invest about $100 million for every pesticide brought to market. This includes exhaustive testing for environmental and human health effects — only to be sabotaged by flukes of nature of our own inadvertent creation.

When a farmer uses a pesticide against a pest, weed, or pathogen, s/he is essentially conducting a field-scale micro-evolution project.

How? The bulk of the targeted population is eliminated. But a few hardy individuals always survive. Some are just naturally resistant — they have a genetic quirk that allows them to thrive in this otherwise hostile environment. We’ve selected them — not through natural, but artificial selection. The “chosen” ones find each other in an otherwise sparse dating pool and mate, passing their genetic peculiarities to their offspring. Each successive generation gets sprayed — but fewer and fewer succumb. Rinse and repeat until every individual scoffs at our attempts at chemical containment.

Biologically, it’s pretty routine. Often, all it takes is a random swap in the four-letter DNA alphabet, like a C for an A. Antibiotic resistant bacteria can follow the same gameplan in human medicine — or they just promiscuously pick up “bonus” resistance DNA from their neighbors.

No doubt, pests have a troubling pedigree at the molecular level. We’ve heard horror stories about palmer amaranth (a weed) resistance to the famed (and historically very effective) Roundup, or the Colorado Potato Beetle to an insane number of different chemistries. No elaborate cocktail is going to take this critter down.

Resistance is often defined as a “messy” and “wicked” problem — something that defies a tidy solution because the goalpost is always in motion. But is it really unsolvable? How do we delay the evolution of resistance and stretch out the useful lifespan of pesticides — essential tools in any farmer’s pest management toolbox (conventional and organic alike)?

Last month, I had the pleasure of attending a workshop to address that very dilemma. Jointly organized by the Entomological Society of America (ESA) and Weed Science Society of America (WSSA), representatives from academia, Extension, governmental agencies, and industry met to discuss progress on a potential national model — the Iowa Pest Resistance Management Program (IPRMP), specifically the Harrison County Pest Resistance Management Project, to combat resistance in America’s heartland.

That’s quite a few acronyms. The main takeaways? Platitudes aren’t going to keep the resistance fairy at bay, so communities need to mobilize to action. Since resistant pest populations don’t respect property lines, “it takes a village” is the best approach. Everyone is an equal stakeholder, so everyone has to on board with an area-wide approach. If just one farmer deviates from the prescribed formula, it sabotages the whole plan. Lone wolves aren’t going to cut it. Farmers, you’re going to have to dispense with the rugged individualism of Jeffersonian lore and work with your neighbors. Rile up the status quo. We’re all in this together.

I was particularly struck by the nods to sociology and psychology. This included building capacity and fostering grassroots buy-in among farmers — and peer pressure/shaming (television dramas focusing on teenage angst immediately came to mind!) for farmers who insist on going at it alone. There was also a focus on voluntary participation (egged on by peer pressure) to get the job done. This appears to be a much better approach than heavy handed, top down mandates from governmental agencies.

Some other points:

  • Democratize the process: Fears over palmer amaranth “superweeds” may get all the press, but locals in Iowa found giant ragweed, marestail, and waterhemp to be more clear and present dangers. Listen and tailor a management program accordingly.
  • Seeing is believing: Build support for changes through on-farm pesticide resistance trials.
  • Be proactive, not reactive: Assume resistance is inevitable. Grow your repertoire of practices and tools. Mix and match. Don’t be overdependent on chemistry XYZ! The best elixir is to use at-risk pesticides sparingly, rotate, and/or tank mix with different chemistries to keep the critters physiology guessing. Use tillage if it’s compatible with your philosophy.
  • Enhance visibility: Maintain a presence in the community and generate awareness about issues as they arise.
  • Don’t be afraid to make course corrections: If surveys and grower discussions reveal an emerging, unanticipated threat, act accordingly. Develop trials to address it.
  • Build a constituency of stakeholders committed to the issue: Though there’s no silver-bullet solution, a multifaceted approach that draws from everyone’s perspectives and expertise is invaluable.
  • Scale the model: Emulate local models and scale to the multistate consortia level. Think local, act global.

Despite their rep with the public, pesticides are essential tools in agriculture. Without them, we’d be relegated to decreased yields, have untenable retail prices, and be at utter mercy of pests, weeds, and diseases all too happy call dibs on our land, livelihood, and next meal. With this valuable resistance management roadmap in place, hopefully we can continue to make inroads in the ongoing battle.


Tim Durham’s family operates Deer Run Farm — a truck (vegetable) farm on Long Island, New York. As a columnist and agvocate, he counters heated rhetoric with sensible facts. Tim has a degree in plant medicine and is an Associate Professor at Ferrum College in Virginia.

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