Used with a smartphone, the handheld device samples airborne volatile organic compounds (VOCs) that plants release through their leaves.
"All plants release VOCs as they 'breathe,'" says Qingshan Wei, an assistant professor of chemical and biomolecular engineering and corresponding author of a paper on the project, "but the type and concentration of those VOCs changes when a plant is diseased. Each disease has its own signature profile of VOCs. So, by measuring the type and concentration of VOCs being released by the plant, you can determine whether a plant is diseased and – if it is diseased – which disease it has."
Current plant disease identification techniques rely on molecular assays, which must be performed in a lab setting and take hours to produce results. Getting a sample to the lab, where the sample may have to wait to be tested, can delay disease identification by days or weeks.
“Our technology," says says Jean Ristaino, William Neal Reynolds Distinguished Professor of Plant Pathology at NC State, co-author of the paper and director of the NC State’s Emerging Plant Disease and Global Food Security cluster, "will help farmers identify diseases more quickly, so they can limit the spread of the disease and related crop damage. We are now ready to scale up the technology."
To use the technology a leaf from the relevant plant is placed in a test tube, which is then capped for at least 15 minutes to allow the relevant VOCs to accumulate. After this incubation period, the cap is removed and a narrow, plastic tube is used to pump the VOC-laden air into a "reader" device connected to a smartphone.
The air is pumped into a chamber in the reader that contains a paper strip, which is embedded with an array of chemical reagents that change color when they come into contact with a specific chemical group. By evaluating the resulting color pattern on the strip, users