The coconut rhinoceros beetle is a major invasive pest that’s hungry for not just coconut palms. The large beetle with its telltale horn also feeds on betelnut, Pandanus palms, banana, pineapple, and sugarcane. On Pacific islands with no natural enemies of this beetle, the damage can be significant.
Enter Dan Jenkins of the Dept. of Molecular Biosciences and BioEngineering and his PhD student Mohsen Paryavi. Armed with a drone that looks like something borrowed from a Transformers movie set, and coordinating with Mike Melzer of the Dept. of Plant and Environmental Protection Sciences and his CRB Response team, Dan recently spent three days at the Hawaiʻi Country Club on Oʻahu, shooting targeted aerial applications of an insecticide called Demon Max (cypermethrin) atop 53 coconut trees that showed signs of infestation.
Arising before dawn in order to avoid the stronger tradewinds later in the day, they sent the drone up again and again, drenching each crown with a ½-gallon of product diluted to 0.5% cypermethrin.
“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,” Dan says. “At my discretion, I treated some highly defoliated trees with approximately half treatments.”
From Dan’s notes:
- Day 1 (June 30): We treated 14 trees, and observed a total of 20 dying beetles (many on their backs twitching, several trying to dig themselves into the dirt) from the base of treated trees.
- Day 2 (July 1): We treated 30 trees, and collected 59 dying beetles at the base of treated trees. Mortalities from the previous day were cleaned up, out of concern of spreading them up the food chain. We placed these collected beetles in their own container in the quarantine facility for observation (to ensure they die).
- Day 3 (July 5): We treated the last 9 trees, and collected 29 dying beetles at the bases of these. (The large number of golfers over the July 4th weekend delayed the last treatment.)
“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,” Dan says.
“Some trees had insect burrows/tunnels at the base of these trees,” he adds, “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?”
For analysis and further study, Dan has created shapefiles showing the locations of treated trees, photos with GPS embedded in the metadata, and a 3- and 6-month timeline for revisiting the golf course.
He may also test the husk, flesh, and milk for traces of cypermethrin, and coordinate with the Hawaiʻi Department of Agriculture’s Pesticides Branch, Syngenta Co., and the CRB Response team on further experimental trials to demonstrate the safety and efficacy of Demon Max in this application, in order to support institutionalization of these treatments for CRB control.
In one of these trials, Dan and Mike have teamed up to treat a tree at the Urban Garden Center and are closely observing how soon and from where dying beetles are emerging.
Watch the KITV Morning coverage of Dan’s drone in action at the Hawaiʻi Country Club.