In the first three months of this project, we started evaluating the performance of a ground penetrating radar (GPR) to map root architecture of HLB-infected citrus trees. The GPR can be used to map tree roots because it is relatively easy to use in the field and it is non-destructive to trees, roots, and the root-soil environment. Numerous tree root scans can be performed and replicated in a short time without interfering with root growth.Although the GPR has been used to detect roots for different plant species, most studies were conducted in controlled environments or in simulations to evaluate signal processing algorithms. Evaluation of the GPR for root detection in an agricultural field setting such as a citrus grove has not yet been conducted. Additionally, many questions remain to regarding the suitability of the technology for studying the impact of diseases on tree root structure and distribution.One objective of this study is to evaluate the performance of a ground penetrating radar to accurately detect citrus tree roots and generate 3D morphology root maps of citrus trees grown in a complex field environment in Florida. To achieve this goal, we are investigating the influence of several limiting factors on the performance of a GPR to accurately detect citrus roots and determine their main structural characteristics. First, single-factor experiments were conducted to evaluate GPR performance. Factors evaluated were: (i) GPR frequency (900 and1,600 MHz); (ii) root diameter; (iii) root moisture level; (iv) root depth; (v) root spacing; (vi) survey angle; and (vii) soil moisture level. Second, two multi-factor field experiments were conducted to evaluate the performance of the GPR in complex citrus grove environments in southwest Florida and to develop 3D morphology root maps.�Experiments were conducted at the citrus research grove of the University of Florida Southwest Florida Research and Education Center (SWFREC) in Immokalee, FL, USA. A ground penetrating radar (GPR) (TRU� Model, Tree Radar, Inc., USA) mounted to a mobile scanning cart and equipped with: (i) a 1,600 MHz antenna, and (ii) a 900 MHz antenna was utilized to generate a 3D map of the root system. The transmitter of the GPR antenna transmits electromagnetic waves (pulses), and the receiver collects the reflectance when an object is detected beneath the soil surface. The relative distance from the starting point was measured with a wheel recorder. A commercial software (TreeWin Roots and TRU Tree Radar Unit) was used to generate root morphology and root density maps. To present the root layout by location and depth, 3D images were created.Our initial experiments showed that the 1,600 MHz GPR was more accurate in detecting citrus roots and their location than the 900 MHz GPR. Upon target (root) detection, the GPR generated a hyperbola in the radar profile; from the width of the hyperbola the diameter of the root was successfully determined when roots were larger than 0.5 cm in diameter. The GPR also distinguished live from dead roots, which is indispensable for studying the effects of soil-borne and other diseases on the citrus tree root system.�