How Drones Can Use Multispectral Imagery to Fight Pests

Jan 09, 2020

By Edward R. Ricciuti

Unmanned aerial vehicles, better known as drones, are constantly being used for new purposes. They help locate lost people, deliver packages, and now have proven their worth at detecting when agricultural crops are being stressed by insect pests, according a paper published in the Journal of Economic Entomology.

The research turns on the fact that plants under stress reflect light waves differently than normal plants. Red reflectance from vegetation, for example, indicates chlorophyll content of the plant canopy and active photosynthesis, and near-infrared reflectance provides information about the cellular structure and intracellular air spaces within leaves, overall canopy coverage, and above-ground biomass.

The study found that that stress to soybean crops caused by the soybean aphid (Aphis glycines) can be detected by drone-based multispectral imagery, which photographs reflected light of several electromagnetic wavelengths in the same image. It can paint a high-resolution picture in wavelengths visible as well as invisible to the human eye and has potential for scouting the presence of not only the soybean aphid but other field crop pests. Combined in an index, the wavelengths detected provide a measure of overall plant health, which often correlates to crop yield.

A New Remote-Sensing Option

Satellites and piloted aircraft have been used for remote sensing of crops but are expensive, low-resolution, and limited by atmospheric conditions and orbital periods. More recently, changes in reflectance indicating stress caused by the aphid have been detected by ground-based measurements, with hand-held sensors, for example.

“Ground-based sensing is a recent development and provides far less coverage than from a drone,” says lead author Zachary Marston, PhD, of the University of Minnesota’s Department of Entomology. “Detecting soybean aphid-induced stress from a drone is the big win.”

Introduced from Asia in 2000, the soybean aphid has hit hard at the soybean-growing heartland of the north-central United States, which produces 75% of the nation’s crop. The United States leads the world in production of soybean, and it is the nation’s most widely grown field crop.

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Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”