Another early-detection method being developed works by smelling huanglongbing infections in trees. This method detects the different scents plants give off.
Researchers at the University of California, Davis have created a test that could lead to advances in fighting huanglongbing (HLB) disease in citrus. Researcher and professor of mechanical and aerospace engineering, Christina Davis, said the test looks for a certain scent. “Volatile organic compounds, also known as VOCs, are smells and odors that emit out of all living systems, so people, plants, animals, bacteria, they all emit odors. Some of them more than others,” Davis said. “We look at those odors from trees and they can be very meaningful. The odors change when the plants get infected, and so you can literally sniff the tree using special instruments and be able to tell whether it is sick or not.”
Davis says the system is extremely small, and very accurate. “Our system uses a small sorbent, about the size of a tictac, that goes out in the field. We hang it in the canopy of a tree and it sits there for two hours and collects all the smells that the tree is emitting,” Davis said. “Then we close it back up, ship it to the lab and then we can do something called mass spectrometry, and that will tell us all of the chemicals that are in that profile. That information can be used to diagnose the tree.”
This system isn’t limited to HLB disease and can be used to identify others. “We are doing some pilot testing in ornamentals. Rhododendrons are a good example of that. They get spread all over the place through distribution centers. If you could test them before they get distributed, if there is a pathogen, then you know you could quarantine it,” Davis said. “So we have been looking at phytophthora infections in rhododendrons as a potential early-detection strategy.”
There are many early-detection methods being developed and Davis said the citrus industry was smart to start this research some time ago. “The citrus industry was very fortunate and very forward-thinking to have seeded grants and seeded roots with so many groups because we’re all different. We each have tests that are complementary,” Davis said. “That information together has the ability to paint a clear picture as to what’s going on, so I have to give a lot of credit to the citrus industry for taking that approach.”