Robots That Can Sniff Out Crop Disease

Georgia Tech engineers have developed a sensor that could save billions in lost crops

Georgia Tech's Micro GC
A one-inch sensor, mounted on a robotic arm, can analyzes compounds emitted by plants to detect disease before it's too late. Georgia Tech Photo: Rob Felt

Each year, U.S. farmers lose up to 12 percent of their crops to disease and another 12 percent to pests. Sickly plants account for billions of dollars in lost profit in the agriculture industry.

The trouble is, plant diseases are hard to spot before it’s too late. By time there are visible symptoms—wilted leaves, for instance, or discoloration—the disease has advanced enough as to be untreatable.

But plants do let their surroundings know when they’re sick or under attack, just not in a way we’ve ever been able to understand in real time—until now. A team of engineers led by Gary McMurray, division head for food processing technology at the Georgia Institute of Technology (Georgia Tech), has developed a method to monitor and decode those messages to allow farmers to identify and treat diseases before they take root. His vision: robotic arms that capture and identify plants' natural disease signals on the fly.

All plants produce natural signals, in the form of volatile organic compounds (VOCs), to alert the surroundings of what’s attacking them. McMurray’s system captures those compounds using a miniaturize version of a gas chromatograph (called a micro GC). The devices, which were originally developed around the turn of the 20th century, are used to separate chemicals within complex samples—in McMurray's case, the gasses a plant emits. As gas is heated and passed through a column, and an electronic sensor detects the compounds the sample contains. 

There’s no pinching or plucking of samples and running them back to the lab for analysis—a process that can take days or weeks to complete. All the information the micro GC needs is in the air, which means treating diseases, or saving plants from them, could get a whole lot faster.

The applications for gas chromatography stretch well beyond crops. The Department of Homeland Security, for instance, uses them to detect certain types of gases and hazardous chemicals. And researchers have are also using them to screen for certain types of digestive disease in humans.

Traditionally, chromatographs have been large devices anywhere from 3 to 10 meters long; advances in nanomaterials and manufacturing have allowed McMurray to create one that’s the size of an 8-volt battery.  

“We could have never built this; even five years ago it wouldn’t have been possible,” he says.

McMurray's micro GC could be mounted to a robotic arm on existing farm equipment, such as a tractor or plow. The arm would hold the device above the plant leaves and gather air samples. A small computer, no more powerful than a basic laptop or iPhone, can then process data from the samples to identify any pathogens; a quick flush of helium prepares the sensor to evaluate its next sample.

Because they're so small, "[we] can build multiple micro GCs onto one robot," McMurray says. “I can have 10, 20, even 100 of them on a single tractor.”

That means one tractor could gather samples from stalks, roots and buds simultaneously.

The micro GC system could also be used to screen all of our food—from fruits to vegetables and grains—for disease. 

“Fresh produce that’s being shipped around [the globe] could be carrying various pests or diseases. If you have some sort of field-deployable or mobile sensor, you could detect the VOCs that come off of the plants,” McMurray postulates. “It could solve some very big problems.”

The team is currently finishing lab testing for the micro GC to make sure its results are consistent with those from larger chromatographs. In August or September, they will run their first field test, in which a researcher will walk a micro GC through peach fields to test for Peachtree Root Rot.

While that initial test will focus on a specific disease, gas chromatography can screen for dozens of pathogens at once, which also distinguishes it from other approaches, McMurray says.

Even with the technology, plant pathologists will still have to map the VOC emissions associated with certain plans and certain diseases.

Plants whose VOC emissions are already well documented will have a leg-up when micro GC screening gets underway; others will require more time and research to diagnose and treat. “The pathogen we chose, no one knows anything about,” McMurray says, “but, for example, there is a lot known about certain fungi.” 

But the Georgia Tech micro GC is an important turning point in usability and scalability, McMurray says.

“What we have we think is unique,” McMurray says, “these new manufacturing processes are opening up a whole new era of sensors.” 

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