Stand-off detection of plant-produced volatile organic compounds using short range Raman LIDAR

Several plant species release volatile organic compounds (VOCs) when under stresses such as herbivore feeding attack. The release of these plant-produced VOCs (i.e. terpenes) triggers the release of active biochemical defenses, which target the attacker. In some cases, the VOCs send cues to nearby carnivorous predators to attract them to the feeding herbivore. Volatile compounds are released both locally by damaged leaves and systemically by the rest of the plant. These compounds are released in large quantities, which facilitate detection of pests in the field by parasitoids. Detecting the plant's VOC emissions as a function of various parameters (e.g. ambient temperature, atmospheric nitrogen levels, etc.) is essential to designing effective biological control systems. In addition these VOC releases may serve as early warning indicator of chemo-bio attacks. By combining Raman spectroscopy techniques with Laser Remote Sensing (LIDAR) systems, we are developing a Standoff detection system. Initial results indicate that is it possible to detect and differentiate between various terpenes, plant species, and other chemical compounds at distances greater than 12 meters. Currently, the system uses the 2(nd) harmonic of a Nd:YAG; however plans are underway to improve the Raman signal by moving the illumination wavelength into the solar-blind UV region. We report on our initial efforts of designing and characterizing this in a laboratory proof of concept system. We envision that this effort will lead to the design of a portable field-deployable system to rapidly characterize, with a high spatial resolution, large crops and other fields.