Managing Coconut Rhinoceros Beetle in infested areas through wide-scale management
Posted on Jun. 24, 2024 / Best Practices, Invasive Species, Arboriculture / Subscribe 0
By: Arisa Barcinas
Coconut Rhinoceros Beetle (Oryctes rhinoceros; CRB) is a threat to palms and other crops in Hawaii. Their primary food sources include Cocos (coconut), Phoenix (date), Elaeis (oil), Pritchardia, Washingtonia, Livistona, and Roystonea (royal). However, they are able to host shift to other crops such as hala, banana, sugarcane, pineapple, and other crops. CRB has spread across Oahu, with devastating impacts to hosts. Collaborative management of CRB is crucial for reducing impacts of CRB.
Figure 1. Coconut Rhinoceros Beetle damage on Oahu.
For proper CRB management, wide-scale adoption of treatments are needed. If only one property applies proper green waste management or palm treatments their efforts may be minimal in the context of their entire area. Neighborhood-wide treatment and management will have the best results for CRB reduction due to the 4 following reasons:
- CRB need two things: palms and breeding sites
CRB needs host plants (like palms) for the adults to feed and decomposing plant material like mulch, compost, logs, or potting soil for the larvae to feed. Adult beetles must feed on a host plant to produce viable eggs.
- Regional population reduction saves trees
Most current treatments including pesticide application and green waste management work by reducing the total population of CRB that are feeding on the trees in the area rather than repelling beetles.
- CRB infests regions, not individual plants
Beetles can fly very far if they need to and one adult may feed on different trees during their life. The infestation is not in a tree or single property but across whole neighborhoods.
- Most properties must manage CRB to have regional improvement
If one property treats its trees and manages breeding material, but nearby properties are unmanaged, the local populations could still be high and all the trees in that zone will be affected (even treated trees).
Figure 2. CRB larvae found in breeding material (mulch).
Green waste management is the most effective way to reduce beetle populations, since CRB breed and develop in any decaying plant material. Common breeding sites are mulch and compost piles, dead stumps, standing dead palms, and potting soil. Green waste management was a key component of control actions in areas with the best control of CRB populations and impacts. CRB can take ~4-6 months to develop from an egg into an adult, so periodic treatment of potential breeding sites is an important tool to manage CRB risk.
Figure 3. Coconut Rhinoceros Beetle lifecycle; photo credit: Aubrey Moore.
There are multiple treatments and management options to kill CRB, or slow growth and disrupt their lifecycle in breeding material. The best practice for reducing CRB risk is to remove all excess potential breeding material, however, for long-term management of material, a CRB treatment should be done every 4 months. This will prevent adult CRB from emerging and causing feeding damage to hosts. Treatments that kill all CRB in green waste can include chipping, hot composting, submersion, steam treatment, fumigation, or incineration. Treatments that will slow CRB developement, kill some CRB, or make it harder for CRB to establish can include grinding, burial, netting, tilling, spreading thin, tarping, insecticides, grazing with animals that can eat larvae, or manual search and removal.
Figure 4. CRB breeding material treatment table.
In addition to breeding site treatments, there are also palm treatments that can be used to help suppress populations. Treatments can include physical treatments, such as netting of palm crowns, or chemical treatments applied through injections, soil drenches, or foliar applications. For each treatment mentioned, more details can be found at CRB Response Treatments.
Oʻahu is currently designated as an infested area, emphasizing the need for community control. For neighboring islands, reporting is crucial to response. Kauaʻi had its first detection of CRB in May 2023. Hawaiʻi Island had its first detection in October 2023. Maui had its first detection in November 2023. For more information on recommendations for individuals located on Oʻahu, please visit crbhawaii.org/treatments. For any signs of CRB found on neighboring islands, please report immediately to the CRB Response at [email protected].
Arisa Barcinas is an outreach associate for the Coconut Rhinoceros Beetle Response.
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