In the ever-evolving world of agriculture, where pests pose constant threats to crop yields and sustainability, Dr. Peter C. Ellsworth stands at the forefront of innovative pest management. 

As a Professor of Entomology and Extension Specialist at the University of Arizona, Statewide Integrated Pest Management (IPM) Coordinator, and Director of the Arizona Pest Management Center, Ellsworth has dedicated his career to developing science-based solutions that balance ecological integrity with economic viability. His research dives deep into the biology and behavior of pests like the whitefly, Lygus bug, and pink bollworm, unraveling their interactions with crops to devise sustainable control strategies. 

Leading multidisciplinary teams and fostering collaborations across borders—such as through the Mexicali Cotton IPM Project—Ellsworth’s work, backed by over 160 publications, has reshaped IPM practices in Arizona and beyond. 

In this exclusive interview, we explore his insights on advancing conservation biological control, navigating resistance management, and shaping the future of pest management in a changing world.

 

Arizona Agriculture: What Does Integrated Pest Management Mean to You?

Dr. Ellsworth: By definition, Integrated Pest Management (IPM) is a strategy that assembles and integrates information and tactics to manage pests while minimizing risks to human health, the environment, and the economy.

But to me, IPM is more than a strategy—it’s a way of thinking. It’s science-led and people-driven, grounded in ecology, risk management, and decision-making. IPM harnesses the power of information and brings it into the field, into the hands of growers and pest control advisors (PCAs) who must make smart choices every day.

It’s not something you’ll see advertised on a bag of produce. But every successful grower uses IPM—even if they don’t always call it that. They have to. It’s how they engineer biological systems to work in their favor. And I do mean engineer. Growers are ecological engineers. They raise living organisms—plants and animals—within ecosystems that include both threats and allies. They make decisions about inputs and interventions, always balancing cost, benefit, and risk.

The brilliance of IPM is in its simplicity: make the best decision possible with the best information available. It’s not about eliminating every pest. It’s about managing systems to achieve economic goals while maintaining ecological balance.

This idea transformed me as a young student. During an era when DDT was king and “womb to tomb” spraying was typical, IPM introduced a radically different philosophy: management over elimination, integration over singular silver bullets. That idea has endured for over 65 years—and continues to evolve. It’s durable, flexible, and still ahead of its time.

Arizona Agriculture: How Did You First Get Involved in IPM?

Dr. Ellsworth: My journey started in the classroom—an ambitious undergrad, I petitioned my way into a graduate-level course in IPM. That experience culminated in a senior project on sunflower IPM in New Hampshire, and I threw myself into the classics of applied insect ecology. Lots of book learning. 

But the real education began later, standing in an Arizona cotton field overrun with whiteflies. Growers were desperate for answers. They had just come off one of the worst pink bollworm outbreaks in history—and now this. The new, invasive whitefly fouled cotton lint with sticky, sugary honeydew, turning fields black with sooty mold. Arizona’s reputation for premium cotton was unraveling.

There were more questions than answers. What was this insect, exactly? How did it behave? How many were too many? What made it thrive—and what could stop it? From the ground up, we began building the foundations of a program that would someday turn this overwhelming pest into a manageable, even minor issue. But at the time, all we had were questions, urgency, and a commitment to figure it out.

Arizona Agriculture: Why Is IPM Important in Arizona Agriculture?

Dr. Ellsworth: Arizona’s unique environment—long seasons, near-continuous plant growth, and unrelenting heat—makes it an ideal proving ground for IPM. But it also means that pest pressure is high. Whiteflies cycle through more generations here than almost anywhere else in the world. 

Historically, growers responded with intense insecticide use. One grower told me he sprayed 25 times in a single season—and still lost his cotton crop. Another showed me his field map and said, “Come July, it’s never a matter of whether to spray—just what to spray. The ag pilot’s on call every Sunday.”

But that was then. Arizona growers and researchers have flipped the narrative. We adopted Bt cotton early. We eradicated pink bollworm. We built resistance management plans that worked across commodities. And we developed predator-based thresholds that now give growers the confidence not to spray. Collectively, cotton growers have saved well over $600 million and avoided applying more than 40 million pounds of active ingredient. Insecticide use is down 95%. That’s not just a win for the environment—it’s an economic lifeline.

IPM’s power in Arizona is its connection of science to action. It works because it’s local, tailored, and trusted.

Arizona Agriculture: What Has Been One of the Most Significant Pest Challenges in Your Work? 

Dr. Ellsworth: Without question, it was the whitefly crisis of the 1990s. But it wasn’t just a pest outbreak—it was a full-blown systems failure.

The invasive B-biotype whitefly arrived like a storm. It had multiple hosts, rapid reproduction, resistance to available chemistries, and virtually no established thresholds or control protocols. It moved fluidly across crops—spring melons to summer cotton to fall melons and winter vegetables—leaving sticky, sooty devastation in its wake. Growers were in crisis, and no one had clear answers.

We had to build the playbook from scratch. What is this pest? How does it behave here? When does it cause damage, and how can we measure risk? That meant basic biology, ecological research, and rapid extension of early findings—all at once.

At the University of Arizona, we partnered with USDA scientists, state agencies, and industry to form a coordinated response. We developed sampling systems and economic thresholds that helped PCAs time insecticide applications with precision. We brokered cross-commodity resistance management agreements—a first in our region—that allowed growers to share modes of action intelligently across multiple crops.

Perhaps most significantly, we introduced new selective insecticides—the first of their kind used against whiteflies in the U.S. These didn’t wipe out everything. They spared natural enemies, which allowed ecological mortality factors to recover. That gave rise to the idea of bioresidual: the notion that a well-timed, selective spray could trigger a cascade of natural suppression that extended far beyond the chemical's direct effect. Where we used to express chemical residual in days, we now express bioresidual in weeks.

Looking back, it was a perfect storm—but it also became a turning point. That crisis laid the foundation for the IPM system we have today.

Arizona Agriculture: How Do You Integrate Chemical and Biological Controls?

Dr. Ellsworth: Today, we’re in a far better place, because we’ve learned how to integrate chemical and biological controls into a cohesive system. And it works not just in theory, but on real farms, with real success.  

One of the most important breakthroughs was what we called bioresidual. We saw that selective insecticides could knock back pests without harming their natural enemies. That ecological “backup system”—the spiders, lacewings, pirate bugs, big-eyed bugs—picked up where the chemistry left off. The result? Fewer sprays, better control, and a more resilient system.

With my long-time collaborator, Dr. Steve Naranjo, we cataloged the community of cotton predators—more than two dozen species—and identified the ones that actually drive control of whiteflies. With further assistance of our Ph.D student, Tim Vandervoet, that led to our development of predator inaction thresholds: simple guidance that tells a grower when not to spray because nature is already working. That’s a powerful message.

PCAs now count predators as carefully as they count pests. We’ve trained them to look for lacewing larvae, Collops beetles, minute pirate bugs, Drapetis flies, crab spiders, and big-eyed bugs. These creatures aren’t just scenery—they’re essential labor in the cotton IPM program.

When insecticides are used, their role has shifted. No longer are they about “wiping the field clean.” Instead, they’re about nudging the system—reducing pest pressure just enough to let predators regain control. For too long, our industry saw chemical and biological controls as competing philosophies. In truth, they’re complementary tactics. It’s not ideology—it’s ecology.

Arizona Agriculture: How Do Arizona Growers Use Your Research in the Field?

Dr. Ellsworth: The biggest reward for an applied scientist? Seeing your work used. And here in Arizona, I’ve been lucky—lucky to work in a professional, progressive agricultural community; ‘lucky’ to have crises that demanded innovation; and lucky to collaborate with some of the best Pest Control Advisors in the country. 

PCAs are the beating heart of our IPM system. They’re licensed, trained, trusted professionals who turn science into strategy. Our work is built for them—sampling plans, economic thresholds, resistance tools, predator inaction thresholds. They take it from research to row crop.

People often think of pest management as new products: insecticides, seed traits, or equipment. But our biggest contributions often aren’t physical—they’re conceptual. They’re the software behind the hardware. We build decision aids, models, and guides that make those products work better. And we give them away, freely, through Cooperative Extension.

That’s the genius of the land-grant model. We don’t sell products—we deliver systems. Systems that help growers make smarter decisions with fewer resources.

One example: resistance management. Most people don’t worry about resistance until it’s already here. We’re trying to get ahead. Right now, we’re building a tool that maps insecticide usage and identifies temporal refuges—times when no selection pressure exists. That allows PCAs to choose chemistries based on actual local resistance risk. It’s proactive, not reactive.

Bottom line: good science gets used. And I’ve seen our science reduce insecticide use by over 90%—while improving control. That’s success.

Arizona Agriculture: How Do You See Technology Playing a Role in IPM Now and in the Future? 

Dr. Ellsworth: Technology has always been central to IPM—and will be even more so in the future. But tech alone isn’t the answer. Trust is the linchpin. Whether we’re using drone imagery or predictive models, what matters most is that PCAs and growers trust the data and the decisions it informs. That’s why education—the soft side of technology—is just as critical as the tools themselves.

A key lesson I’ve learned is that tech that does not earn user trust won’t be adopted no matter how brilliant it is. IPM, at least in Arizona, has credibility because of the major achievements to date. Trust is what bridges the gap between data and decision. We’re entering a world where there’s so, so much data. IPM was and is data-driven. In my role as an Extension Specialist, I hope that I can help design trusted solutions that bridge that gap. No matter how much tech we develop, farming still relies on people. Our science and implementation must keep people at the center of all that we do.

Arizona Agriculture: What Are Common Misconceptions About IPM? 

Dr. Ellsworth: A lot of people think IPM means “never spray.” It doesn’t. It means spray smart — spray when it’s needed, what is needed, and only as much as needed. Our job is to minimize risk: to people, to ecosystems, and to the bottom line. Sometimes that means spraying. Often, it means waiting, or choosing something softer, or doing nothing at all—because the system is working.

Another misconception is that IPM is too complicated or expensive. That might be true somewhere, but it’s not true here. In Arizona, we’ve proven that selective insecticides, though more expensive per gallon, actually save money by reducing overall spray frequency and preserving beneficial insects. The “cheap” option often comes with hidden costs.

And then there’s the idea that IPM is hard to teach or apply. Sure, the science is complex. But implementation doesn’t have to be. We publish simple tools: a two-page chart color-coding insecticides by selectivity. A one-page sampling guide titled “In 7 Minutes or Less.” Beneath that simplicity is rigorous ecology and math. But for the grower or PCA in the field? It’s grab-and-go guidance. That’s what IPM should be—usable science.

Arizona Agriculture: What Are You Most Proud of in Your IPM Work?

Dr. Ellsworth: Can I just say—surviving? The early 1990s were brutal. Pink bollworm, whiteflies, 13-spray seasons. At the time, I couldn’t imagine being here three decades later, still working on IPM and still seeing growers use what we’ve built together. 

I’m proud of our work on predator inaction thresholds—one of the few operational models in the world that guides growers on when not to spray based on active biological control. That work stands on the shoulders of 65 years of IPM theory and finally delivers something practical, field-ready, and adopted.

I’m proud of our success in integrating chemical and biological controls, not as opposing camps, but as allies in a larger system. That harmony is rare in global IPM, and it reflects both the strength of our science and the openness of Arizona growers.

But most of all, I’m proud of the community we’ve built—scientists, pest control advisors, growers—all pulling in the same direction. That unity is the real engine behind IPM’s success.

Arizona Agriculture: What Advice Would You Give to the Public—or the Next Generation—About Science, Agriculture, and IPM?

Dr. Ellsworth: Agriculture is applied ecology. It’s systems thinking with real-world stakes. If you love solving puzzles that feed the world and protect it at the same time—IPM is your calling. 

The world is changing fast. We’re training students today for jobs that don’t yet exist. But one role will always matter: the translator—the person who takes science and turns it into something useful. In agriculture, that person often lives in Extension.

Working in the public sector, on behalf of real people, in real time, is both a challenge and a privilege. You’re not publishing for tenure—you’re publishing to save a crop. You’re not doing research for curiosity’s sake—you’re doing it because someone’s livelihood depends on it.

Science is under scrutiny. Public investment is in question. But the value of applied, trustworthy, transparent science has never been higher. If you want a career that’s hard, humbling, and full of purpose—step in. We need you.

Editor's Note: This article originally appeared in the May issue of Arizona Agriculture