Researchers in the Academy’s Department of Biology here are developing a low-cost solution to detect infected trees using Unmanned Aerial Vehicles.

There are more than 9,884 acres of woodland forest on the academy, dominated by ponderosa pine trees. Several years of severe drought thinned the forest and reduced the health of the surviving plants. Infestations by pine beetles and mistletoe have followed, which destroy the trees’ vascular systems and dehydrate the tree and have played a significant role in decreasing the overall health of the forest.

The economic -- dead trees must be removed at a considerable cost, which doesn’t always stop the spread of parasites -- and biological impact represents a considerable problem for the academy.

A dying tree is easy to identify after it has become infected. It is possible to detect diseased trees before the beetle has left the tree or mistletoe has dropped seeds, but doing so requires expensive multi-spectral satellite imagery, which isn’t available to the academy or forest installations combating a similar infestation.

And so, an idea took flight to help solve the problem.

The idea is to fly a UAV over the trees with a sensor that can detect which trees have the beetle in them by measuring the amount of moisture in the pine needles.

Currently, the department is working to develop a correlation between the infrared signature and the water potential of the pine needle.

“An IR sensor mounted on a UAV can determine a tree’s water potential,” said Maj. Jerry Krueger, assistant professor of biology. “If we fly in the wet season, like April after the snow pack has melted, we know that any dehydration is likely caused by beetles or mistletoe.”

Four cadets in field ecology are working to refine the model for the IR signature of the pine needles. This work involves the collection of pine needles, and using a plant pressure chamber to assess their water status. Then using a spectral-radiometer in the geography department, they obtain their reflectance signature.

“Our goal this semester is to build that mathematical relationship,” Major Kruger said. “What IR wavelength allows us to see hydration in plants? This kind of work has been done on food crops, but no one has looked at this particular aspect before.”

To obtain data, cadets must get needle samples from healthy and unhealthy ponderosa trees, and then determine their hydration limits in the plant pressure chamber. Then they use the spectral-radiometer to find a wavelength that will determine a corresponding IR signature for each hydration level.

Academic departments have been involved in this unique interdisciplinary project to varying degrees over the last two years. When the idea was originally conceived, they realized that finding a solution to the infestation would not only provide cadets with excellent research opportunities and a chance to expand their experience by working with other departments. Also, by involving other departments, the project could save a great deal of money by using infrastructure and expertise that was already available.

Col. Paul Pirog, the Department of Law chair, got involved in the project as a result of informal conversations with the faculty. He was interested in the academy’s legal responsibility to try to check the spread of parasites, and later in the liability for a UAV crash, once the project was ready to go.

“As I was running near the overlook one afternoon, I noticed a number of dying Ponderosa pines and wondered what was killing them and how it could be prevented,” Colonel Pirog said. “Major Krueger happened to have some data on IR reflectivity of pine needles versus their water potential. After some exciting discussions which included using a flying platform to identify the sick trees, we launched a call for other departments to see if they would like to join in.”

“As a JAG, we are interested in not only legal questions, but in the science behind how things work (or break) so that we can provide even better legal advice,” Colonel Pirog said. “As an educator, we used this problem as a legal independent research project for a total of three cadets during the two years it was active.”

One cadet concentrated on the legal aspects of the environmental plans to remediate the beetle infestation, while another cadet concentrated on the tort law aspects of a UAV crash and laid the groundwork to begin looking at UAV airspace management issues. The third cadet concentrated on intellectual property issues to obtain needed UAV parts, ethics issues related to acceptance of gifts for the project, and finalizing the airspace management issues between the research group and airfield management.

“The main lesson that cadets learned -- besides the substantive areas they focused on -- is that communication and teamwork is the secret to successful mission accomplishment,” Colonel Pirog said. “The teams who worked on the project were more compartmentalized than we had hoped for, and it ended up showing in some of their work. The students also learned about accountability and responsibility since this project was challenging and complex -- and even limited success required unlimited effort.”