Killer drones tackle pest infection

Researchers have used “killer drones” to fight an infestation of pests which threatened to destroy agriculture across Hawai’I, in a move which they believe can be replicated across the world.

The coconut rhinoceros beetle (CRB) is a major invasive pest that feeds on coconut palms, betelnut, Pandanus palms, banana, pineapple and sugarcane. In Hawai’i, with no natural enemies to this beetle, the damage to crops has been and can be significant.

A team from the University of Hawaiʻi at Mānoa College of Tropical Agriculture and Human Resources, led by professor Dan Jenkins of the molecular biosciences and bioengineering department and his PhD student Mohsen Paryavi were tasked with finding a solution to the pest. Armed with a specifically designed drone the academics coordinated with Mike Melzer of the Department of Plant and Environmental Protection Sciences and his CRB Response team to combat the CRB.

Jenkins recently spent three days at the Hawaiʻi Country Club on Oʻahu, using the drone to shoot targeted aerial applications of an insecticide called Demon Max (cypermethrin) on coconut trees that showed signs of infestation.

beginning before dawn in order to avoid the stronger tradewinds later in the day, the team sent the drone up repeatedly, drenching each tree’s crown with a half-gallon of product diluted to 0.5% Demon Max.

“Most of the trees were defoliated enough that we really applied directly in the crown—in contrast to healthy trees where fronds grow straight up and occlude the crown,” said Jenkins. “At my discretion, I treated some highly defoliated trees with approximately half treatments.”

On the first day, 14 trees were treated and a total of 20 dying beetles were observed from the base of treated trees. On day two, 30 trees were treated and 59 dying beetles were collected at the base of treated trees. As the project continued mortalities from the previous day were cleaned up, out of concern of spreading them up the food chain. The collected beetles were placed in their own container in the quarantine facility for observation.

“One observation is that virtually all of the beetles we found were at the bases of trees that had no other vegetation or long grass at the base (approximately half of the trees), so I would think that we killed at least double what we were able to find,” said Jenkins.

Jenkins added, “Some trees had insect burrows/tunnels at the base of these trees and where they existed, we collected a lot of beetles trying to dig further into them. We also found a lot of centipedes in this kind of habitat—possibly trying to predate on the beetles?”