Drones with claws and chainsaws are flying over Big Island forests, thanks to the invention of a University of Hawaii professor.
Kukuau is a six-rotored remote-controlled drone equipped with a chainsaw and a robotic arm capable of grasping, cutting and carrying objects up to 7 centimeters — about 2.75 inches — in diameter. But despite its bladed armaments, Kukuau is not the latest weapon of a movie villain, but a new tool to more effectively detect the spread of rapid ohia death.
Ryan Perroy, a professor at the University of Hawaii at Hilo’s Department of Geography and Environmental Science, and a Swiss research team developed Kukuau — a Hawaiian name for a species of crab — to take aerial samples of trees suspected of being infected with the fungus that causes ROD, which has killed millions of ohia trees on the Big Island.
“There are certain situations where we suspect that a tree has been infected with the pathogens that cause ROD, but it’s difficult or dangerous to send crews to the tree itself to get samples,” Perroy said.
In situations like this, Perroy said, Kukuau is able to descend upon a tree from above to cut off and retrieve samples of its upper branches for analysis.
Perroy said that a Swiss research team from ETH Zurich, a public research university, had sent UH a similar instrument several years ago, but it was too small to collect branches large enough to detect signs of the fungal pathogen.
So, with a lot of iterative engineering work and the assistance of R&R Machining/Welding in Hilo, Perroy and the Zurich team developed a more robust machine capable of lifting branches of about 4 pounds.
“The problem with the smaller branches is they dry up faster, and you can’t determine from them if the tree is infected,” Perroy said. “What I was trying to do was figure out what’s the smallest possible diameter branch you need to detect the disease.”
Since the development of Kukuau, Perroy said the drone has retrieved dozens of branch samples and detected ROD in about 77% of them. Perroy published his findings about the use of Kukuau for ohia sampling in the scientific journal Drones.
Unhealthy ohia trees typically develop a reddish-brown tint in their canopies, Perroy said, which can be easily detected via aerial photography. But not all unhealthy ohia trees have ROD, hence the need for sampling.
When a tree has been confirmed to have the disease, it may be felled to prevent the spread of the pathogen to other trees, or it may be kept standing, depending on its location. In the case of Kukuau, most of the trees it samples are located in places where they could at least be reached and felled by forester crews.
Because of Federal Aviation Administration requirements regarding unmanned aircraft, Kukuau is not permitted to travel beyond the line of sight of its operator. It is also not allowed to carry flammable liquids, so Perroy said significant engineering work was done to make the machine “self-lubricating” without the need for flammable oils.
The FAA also has restrictions against using aircraft to transport plant matter, but Perroy said he obtained a certificate from the FAA allowing Kukuau to legally transport tree samples.
Perroy said Kukuau “will never be completely finished,” as it will be continually improved upon and altered as time goes by. He added that collecting ohia samples is not the machine’s only utility, suggesting that it could also be used for collecting and propagating endangered species or simple aerial tree pruning.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.