April 2018: The Hawaii Department of Agriculture has released a pest advisory for an invasive beetle attacking cacao and Sago palms on the east side of the Big Island. The beetle, Acalolepta aesthetica, is believed to have been accidentally introduced through imported commodities from the Queensland region of Australia. Beetles in this family, the Cerambycids, are wood-borers and are known to burrow into wooden packing materials. Acalolepta aesthetica is related to the Asian longhorn beetle, infamous for devastating forests in North America with estimated costs for control more than $600 million since the 1990s.
The Australian longhorn beetle appears to have first arrived in Hawaii about a decade ago. The first sample was turned in from the Orchidland area in 2009, but for several years after, there were no reports. However, in 2013, HDOA received 3 more submissions, with a handful of beetles appearing each subsequent year. By 2017, it appeared the beetles had begun to spread, with specimens collected in Hawaiian Acres, Kea’au, and Kurtistown.
Adult beetles will feed on the bark, branches, and leaves of preferred plants, but the real damage is caused by the larvae. The females lay eggs in wood, usually in stressed, dying, or weakened trees. The emerging larvae will tunnel through the tree’s vascular system, creating tunnels that weaken the wood and interrupt the plant’s ability to transport nutrients and water. In one case in Puna, an infested Sago palm became so weak it collapsed under its own weight.
In addition to cacao and Sago palms, A. aesthetica may attack other hardwoods present in Hawaii: breadfruit, candlenut, citrus, gunpowder, and notably, the native Hawaiian lama tree (Diospyros sandwicensis).
There is no known treatment for an infestation of A. aesthetica. Adult beetles appear to be attracted to light at night, where they can be collected. HDOA advises that routine IPM insecticidal applications may deter adult beetles from selected areas; however, research is needed to determine how to address beetle infestation. The best strategy is prevention: be very cautious in moving potential host plant species from the infected area between Kea’au and Pahoa. Trees infested with the larvae should be destroyed.
If you believe you may have the Australian longhorn beetle on your property, or if you discover a specimen outside of the middle-Puna area, pleas call HDOA at (808) 974-4146 or email them at firstname.lastname@example.org.
More information is anticipated from the Hawaii Department of Agriculture, and we will post that when it is released.