Detection of water content using ground-penetrating radar to save the Ohi'a tree
According to http://faculty.geog.utoronto.ca/Chen/webdata/papers_forJing201501/Plant_Soil_2009_Hirano.pdf , It has been reported that ground-penetrating radar (GPR) is a nondestructive tool that can be used to detect coarse roots in forest soils. However, successful GPR application for root detection has been site-specific and numerous factors can interfere with the resolution of the roots. We evaluated the effects of root diameter, root volumetric water content, and vertical and horizontal intervals between roots on the root detection of Cryptomeria japonica in sand using 900-MHz GPR. We found that roots greater than 19 mm in diameter were clearly detected. Roots having high volumetric water content were easily detected, but roots with less than 20% water content were not detected. Two roots that were located closely together were not individually distinguished. These results confirm that root diameter, root water content, and intervals between roots are important factors when using GPR for root detection
and that these factors lead to an underestimation of root biomass.
That means GPR can detect tree that have more water and less water. Since the ROD infected Ohi'a tree have less water it is likely that the GPR will detect it and that can be used as a device to detect the ROD fungus.

Comments are welcomed!!!
 
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I second this idea of ground-penetrating radar.
According to https://www.fs.usda.gov/treesearch/pubs/56941
It was found that the GPR scan was sensitive to the presence of internal moisture, which will be useful in locating areas of potential decay.

Here is the article description:
This report describes the testing plan and preliminary results in an ongoing project to assess the efficacy of using ground-penetrating radar (GPR) to detect internal moisture and fungal decay within Douglas-fir beams. Initially, the test beams were assessed using a variety of physical, mechanical, and nondestructive evaluation (NDE) test methods including micro-resistance drilling, Janka hardness, stress wave transmission, and GPR. After initial baseline assessment, test beams were inoculated with brown-rot fungus, Fomitopsis pinicola, and exposed to just above-ground conditions 22 miles (35.4 km) north of Gulfport, Mississippi, USA. Test beam specimens were inspected in the field at 6, 12, and 17 months of exposure using GPR, moisture measurements, and stress wave transmission. Select specimens were removed from the field during each site visit and returned to USDA Forest Service, Forest Products Laboratory, where the NDE tests were repeated. In addition, computer tomography (CT) scans were taken of a subset of the returned specimens. Finally, destructive Janka hardness testing provided insight into mechanical property change during exposure. The GPR scans were compared with the NDE, CT scans, and hardness results. It was found that the GPR scan was sensitive to the presence of internal moisture, which will be useful in locating areas of potential decay.
by Tersha Carpenter
Thank you very much @Tersha Carpenter for the additional information. I thought I was working on this alone and it feels safe you are working on it too. It would be great if we work together so either create this project and invite me to join or join mine which already has been created months ago if you are interested of course.
by Anteneh Gashaw
@Tom Quigley I think you should see this and let me know your thought because your team has commented many concerns on this proposal via my email and this might change your perspective.
by Anteneh Gashaw