(Nanowerk News) Researchers from North Carolina State University have developed an electronic patch that can be applied to plant leaves to monitor plants for various pathogens — such as viral and fungal infections — and stresses such as drought or salinity. In testing, the researchers found the patch was able to detect viral infection in tomatoes more than a week before growers could detect visible disease symptoms.
“This is important because the earlier growers can identify plant diseases or fungal infections, the better will be their ability to limit the spread of the disease and preserve their crops,” said Qingshan Wei, corresponding author of the paper on the work (“Abaxial leaf surface multimodal wearable sensor for continuous monitoring of plant physiology”) and assistant professor of chemical and biomolecular engineering at NC State.
“In addition, the sooner farmers can identify abiotic stresses, such as irrigation water contaminated by saltwater intrusion, the better will be their ability to address relevant challenges and increase crop yields.”
The technology builds on patches of earlier prototypes, which detected plant diseases by monitoring volatile organic compounds (VOCs) emitted by plants (Affairs, “Real-time monitoring of plant stress through chemiresistive profiles of leaf volatiles with wearable sensors”). Plants emit different combinations of VOCs under different circumstances. By targeting VOCs relevant to a particular disease or crop stress, sensors can alert users to specific problems.
“The new patch incorporates additional sensors, which allow them to monitor temperature, environmental humidity and the amount of moisture that plants ‘exhale’ through their leaves,” said Yong Zhu, co-author of the paper and Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State.
The patch itself is small – only 30 millimeters long – and consists of a flexible material that contains sensors and electrodes based on silver nanowires. Patches are placed on the undersides of leaves, which have a higher density of stomata – the pores that allow the plant to “breathe” by exchanging gases with the environment.
The researchers tested the new patch on tomato plants in a greenhouse, and experimented with patches that incorporated various combinations of sensors. Tomato plants are infected with three different pathogens: tomato spot wilt virus (TSWV); early blight, which is a fungal infection; and late blight, which is a type of pathogen called an oomycete. Plants are also exposed to various abiotic stresses, such as overwatering, drought conditions, lack of light, and high salt concentrations in the water.
The researchers took data from these experiments and fed it into an artificial intelligence program to determine which combination of sensors worked most effectively for identifying disease and abiotic stresses.
“Our results for detecting all these challenges are very promising,” said Wei. “For example, we found that using a combination of three sensors on a patch, we were able to detect TSWV four days after the plants were first infected. This is a significant advantage, as tomatoes usually do not start showing physical symptoms of TSWV for 10-14 days.”
Researchers say they are two steps away from having a patch that growers can use. First, they needed to create a wireless patch – a relatively simple challenge. Second, they need to test the patch in the field, outside of the greenhouse, to make sure it will work in real-world conditions.
“We are currently looking for industrial and agricultural partners to help us move forward in developing and testing this technology,” said Zhu. “This can be a significant step towards helping farmers prevent a small problem from becoming a big one, and helping us tackle food security challenges in a meaningful way.”