Rhinoceros Beetle Update: Treatment Plan for Seacliff
Dear Seacliff Owners,
We want to keep the community informed about the rhinoceros beetle infestation affecting palm trees across Oʻahu and Kauaʻi, including here at Seacliff.
Overview
Rhinoceros beetles are spreading aggressively, feeding on palm sap and laying eggs in mulch, green waste, stumps, and other decaying organic matter. Mature coconut palms are especially vulnerable, and the beetles can fly up to roughly 2.5 miles, making the infestation difficult to contain. Other varieties, including foxtails and royals, are also at risk.
What We’ve Tried
Several treatment methods have been evaluated, each with real limitations: netting requires full, gap-free coverage and becomes less effective over time; organic sprays and deterrents (basil oil, cayenne, soap, chili water) wash off in rain, need weekly reapplication, and can burn foliage in heat; and injections or traditional spraying have shown mixed results (roughly 50% retention in comparable Wailua trials), with climbing to treat trees being hazardous. Most current methods slow the damage rather than eliminate the threat, and a biological control is hoped for but not yet available.
Recommended Approach: Drone Application
The method we’re now pursuing is drone-based spraying, offered by a Big Island–based vendor with inter-island operations. This approach treats trees from above immediately after trimming — eliminating the need to climb, and treating roughly 50 trees per hour — and has shown positive early results in recent county and state park contracts on Maui. See our recent post on the Aloha ʻĀina Drones video for more on how this works.
Where Things Stand
Trees have recently been trimmed in Aliomanu, and treatment there has been approved by their association. We’re awaiting results on survival rate, efficiency, and overall effectiveness of this new technique before proceeding further. In the meantime, lower-cost measures like traps and small-scale oil/soap trials continue, with monitoring focused on the most heavily impacted areas.
What’s Next
We’ll continue gathering vendor quotes, observing results on the treated property, and monitoring emerging solutions, including biological controls. Pricing isn’t finalized yet, as the vendor is still refining their product and application method — we’ll share updated cost estimates and findings as soon as they’re available.
Stay tuned for more information in the coming months.
Mahalo,
Garret Santos
Association Manager
Seacliff Plantation at Kilauea Bay Community Association