New pest alert! Ramie moth (Arcte coerula, Noctuidae) in Hawaiʻi

Mamaki, Pipturus albidus (Urticaceae), is an endemic Hawaiian species which occurs in mesic and wet forests at a range of elevations on all the main Hawaiian Islands. It is the host plant of the endemic Kamehameha butterfly Vanessa tameamea (Nymphalidae), one of two endemic butterflies in Hawaiʻi, as well as the endemic moth, Udea stellata (Crambidae). Native Hawaiians traditionally use mamaki as a source of medicinal tea, and for its fibers to construct cloth and rope. Commercial production of mamaki as a tea is currently increasing in Hawaii, with plantings on Maui and the Big Island. In 2019, the large, brightly colored larvae of Arcte coerula (Noctuidae) were reported on Maui, feeding on mamaki. Native to Southeast Asia, this caterpillar has been observed to cause extensive feeding damage and defoliate large number of leaves in both native forests and local nurseries on Maui. Current studies are focusing on the distribution and phenology of A. coerula, the extent of its damage, and the impacts of resident parasitoids on both the eggs and larval stages. Ongoing surveys have not yet determined the overall impact of this new pest on Hawaiian ecosystems. Hawaiʻi is home to a number of endemic species in the Urticaceae family, all of them potential hosts of A. coerula. These plants have conservation and commercial value, and preventing further negative impacts from this invasive species is extremely important.