Finding ways to better listen to plants will go a long way in protecting them from pests and diseases, but deciphering their language can be a challenge without the proper tools.

Electronic sensors attached to plants allow researchers to do just that: Listen to plants.

On Dec. 3, North Carolina State University hosted its Stewards of the Future conference that brought in international experts on plant volatiles and communicating with plants with sensors. The experts at the conference agreed that sensors could be the next big thing in precision agriculture.

In the future they believe farmers will be able to use sensors to translate the language of plants and use that data  to provide early  warnings before damage from insects and other pests occurs.

The research is still in its infancy, but progress is being made. Dr. Steve Lommel, associate dean for research at North Carolina State’s College of Agriculture and Life Sciences, considers sensors to represent  precision agriculture at its best.

“One day in the not-so-distant future, every plant in every field in every county in every state in this country will be sending waves of big data to our growers, letting them know with intricate precision the best way to farm,” Lommel said.

Dr. Nasie Constantino, a postdoctoral researcher in the Department of Entomology and Plant Pathology at North Carolina State, discussed the work she and her colleagues are doing using small sensors coated with polymers that can detect volatile organic compounds (VOCs) that plants emit in response to different stressors.

“During times of stress, plants release volatile organic compounds which activate various responses in plants. Each compound is specific to each type of stress. What we are looking to do is use sensors to exploit those different types of volatile compound blends and use them to identify what stress the plant is under,” she explained.

“The sensor is very small and low powered and wireless, about the size of a quarter which makes it easily deployed,” she added. “Our sensor includes a multi- channel sensor ray. We can have up to six channels. It also involves a blue tooth module making it wireless and able to transfer data to our computers. It also has a low powered custom read out integrated circuit and it is powered by a coin cell battery allowing it to be operational for several months.”

The research is still in its early stages and Constantino and her colleagues continue to collaborate to further refine the sensor. In one project, they examined the VOCs emitted by corn plants when wounded or attacked by an insect.

“Once the sensors are coated with the polymers and activated, they have a baseline frequency where they vibrate. Once they encounter the specific volatiles, their frequency will shift downward from the added weight of the volatiles on the sensors. Once the volatiles are released, they will go back up to their baselines to indicate the sensors have detected a volatile. We are looking for the downshift in our frequency,” Constantino explained.

Each of the six channels on the sensor can be coated with a different type of polymer that can interact with different types of volatiles. Constantino and her team can then determine the pattern or each of type of attack and make a fingerprint to identify what type of stress the plants are under.

In their research, the North Carolina State scientists first started with just one channel. “We added a small corn plant to our volatile chamber along with our sensors and we sealed them up, so we are actually setting the systemic volatiles from the leaves as we loaded the stems,” she explained.

“We then mechanically wounded our stems and almost instantly we got a detection in our sensors. We did this two more times. What is interesting about the third time it seems there was a greater frequency shift indicating that maybe the plants are self -priming for the next mechanical movement,” she added.

Once the scientists discovered the sensors could detect volatile compounds with one channel, they moved to three channels coated in polymers as well as a reference channel. They performed two experiments: the first one a mechanical wounding of the plant and the second being a systemic response to injecting the insect diversion instead of mechanically wounding the stems.

“We let the sensors stabilize for 10 minutes. When the 10 minutes were up we wounded them and then allowed the sensors to read for another 10 minutes. Within five minutes the sensors had their frequency downshift and began up to stabilize,” Constantino noted.

“What is interesting about these two different types of treatments is that not only their patterns are quite different, they actually have different frequency shifts, a lot greater than our mechanical wounding. We also do have a reference channel on these sensors that measures pressure, temperature and humidity,” she said.

The pressure and temperature remained fairly stable, but they did see an increase in humidity once the plant had been wounded. “This was most likely caused from the release of moisture from plants due to the wounding,” she said.