A live ramie moth (Arcte coerula) caterpillar was discovered on Kauaʻi last month, marking the first detection of this invasive species on the Garden Isle.
The discovery from a community report to the Kauaʻi Invasive Species Committee has sparked a swift response from the University of Hawaiʻi at Mānoa, the Department of Land and Natural Resources, and the Hawaiʻi Department of Agriculture and Biosecurity.
Growing threat to native ecosystems
Ramie moth caterpillars are prolific feeders known to quickly defoliate māmaki (Pipturus albidus), a native Hawaiian plant vital to our forests and culturally significant for its use in lāʻau lapaʻau, traditional Hawaiian healing practices.
“We are really worried about this because we’ve seen it spread from Maui to the Big Island in 2020, then to Oʻahu in 2024, and now to Kauaʻi,” said Michelle Au, a graduate student at the UH Mānoa College of Tropical Agriculture and Human Resilience (CTAHR) who has been tracking the pest since 2019.
Au highlighted the broader ecological risk: the caterpillars also feed on other endemic nettles including endangered species like maʻoloa (Neraudia angulata). The ramie moths also compete for the same resources with native species such as the Kamehameha butterfly and endangered endemic land snails.
Finding natural predators
As the moth continues its rapid expansion across the islands, Au’s research has focused on the detection of resident natural enemies that could help manage this pest. “We’ve been looking for predators and parasitoids already in our environment that may expand its host range and attack the eggs, caterpillars, and adults of the ramie moth, helping to manage populations from devastating levels,” Au said.
Au’s research monitors specimens at various field sites to determine what percentage of ramie moth eggs reach adulthood, which then will lay eggs and inflict future damage.
Community help needed
“I rely heavily on public reports of this pest, especially for new detections,” Au said. “The biggest thing for us right now, especially for Kauaʻi, is to raise awareness in order to track the spread of this pest.”
Officials ask the public to report sightings with photos to 643pest.org or email ipmlab@hawaii.edu. Visit CTAHR’s extension page on the ramie moth for more information.
