Dr. William Cheung is a chemist working for the Department of Mechanical and Aerospace Engineering, UC Davis.  In this photo he is sampling a navel orange tree at Lindcove REC that is infected with Citrus Tristeza Virus (CTV).  He is using a device that utilizes Differential Mobility Spectrometry (DMS) to detect diseased plants that appear healthy.   Stressed or diseased plants release unique volatile organic metabolites resulting from host-plant interactions, which can be detected by DMS.  The device fits into the small metal case pictured here, and is connected to a laptop PC.  Dr. Cheung’s group is currently testing a similar DMS device to detect Huanglongbing (HLB) in Florida citrus.  The group hopes to develop a robotic platform that will automatically move the device throughout an orchard, sampling each tree as it moves along.