The Coconut Rhinoceros Beetle (Oryctes rhinoceros), or CRB, is an invasive beetle that has established itself on Oahu and Kauai and may be gaining footholds on other islands. Adult beetles fly to a palm at night and bore into the "heart of palm" at the core of the crown of the tree. The heart contains tasty sap and tissue, and also contains tightly packed young fronds which have not yet emerged. When a CRB bores through the heart it damages the young fronds, and when those fronds emerge they will contain characteristic V-shaped notches or cuts that look like a scissors was used to cut the fronds. CRB do not live long periods in the tree, rather they visit regularly, and each feeding creates cumulative damage that will eventually kill the tree.
The critical detail for protection: beetles usually enter the crown through the crevices between the frond bases and the trunk. Those crevices are a small, well-defined set of entry points. Guard them, and you guard the tree.
Research in Hawaii and elsewhere has shown that certain plant essential oils repel Coconut Rhinoceros Beetles and can kill them on contact. That's why botanical oils appear among the recommended CRB control tools. The catch is durability: oils applied to a tree directly — neat or as a spray — evaporate and break down within a week or two in the tropical sun, so keeping a palm protected that way means reapplying every few weeks. For a tall palm that's climbed or reached by lift only a few times a year, that just isn't practical.
So the real problem to solve was never whether essential oils deter CRB. It was how to keep them on the tree, working, for months at a time.
CRB Defense Wax Cups solve the durability problem by carrying the oils in a soft, natural beeswax formulation engineered for exactly this job:
Each 2-ounce cup is a pre-measured dose. A bag of 15 cups treats one tree; larger palms may take up to 20 cups. Applied at trimming time, the wax protects the entry points until the next trimming — about three months.
CRB Defense Wax Cups use a blend of three essential oils — clove oil (rich in eugenol), cedarwood oil (rich in cedrol), and thyme oil (rich in thymol). These are three chemically distinct plant-defense compounds, chosen to combine complementary repellent effects rather than relying on any single one. All three are recognized by the EPA as minimum-risk pesticide active ingredients — the same oils found in natural insect repellents used around homes and gardens.
Wax cups have been protecting palms in the Lanikai neighborhood of Kailua since late 2025, in an area of active CRB infestation, through free distribution to residents and the work of local tree trimmers. Our accumulated experience to date: treated trees that were free of CRB damage have stayed free of damage, and trees that already had CRB damage, once treated and kept on the program, have recovered and pushed out healthy new fronds. That's field experience rather than a controlled scientific study — but it's consistent with the published research on essential oils and CRB, and it's why neighbors and tree trimmers keep coming back for more cups.
A common misconception is that if you inject your trees with insecticides that it will repel CRB. Actually what happens is the CRB still come to the tree and munch on the heart of the palm, until they have injested enough poison to die or get sick. They then die in place, fall out of the tree, or fly away. Other CRB then come to the same tree and also munch on the heart, leading to cumulative damage. Tree trimmers we have talked to say that injected trees often don't do well, probably because they are still being munched on. In this sense, injected trees are essentially "sacrificial" trees, dying for the benefit of other trees in the area.
Thus, injected trees also need to have their crowns protected so that CRB are repelled in the first place.
Wax cups guard the crown — the beetle's doorway into the tree. For best results, combine them with the other proven measures: crown netting where practical, and removing or managing CRB breeding material (mulch piles, decaying green waste, standing dead palms) on your property. Trees already damaged by CRB can often be rescued: trim, treat, and keep the protection refreshed.
This product has not been registered by the United States Environmental Protection Agency. CRB Defense Hawaii represents that this product qualifies for exemption from registration under EPA's Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Section 25(b) as a minimum risk pesticide.
Precautionary Statements: For outdoor use only. Keep out of reach of children and pets. Store in a cool, dry place away from direct sunlight.
CRB Defense Wax Cups are the subject of a pending U.S. patent application. U.S. Patent Pending.