Protecting mamaki from invasive species
The Kamehameha butterfly, the state insect of Hawaii, is found nowhere else in the world, and neither is the plant that feeds and supports the caterpillars as they develop into adults. Mamaki is the main host for this native butterfly and supports other rare forest inhabitants such as the udea moth, happy-faced spider and various species of Hawaiian tree snails. Mamaki is also an important food source for the endangered alala (Hawaiian crow).
A member of the nettle family (Urticaceae), mamaki lacks the stinging hairs of its continental cousins. Mamaki tea is revered as a general health tonic and has become a popular local product. Traditionally, Hawaiians have many uses for mamaki. The wood is used to make clubs and kapa beaters (ie kuku), and the inner bark is beaten to make a fine quality kapa. The fruits, seeds, leaves and bark are used medicinally during pregnancy, for healing sores and wounds, as a mild laxtive and more.
Mamaki’s importance to native animals and Hawaiian culture is undeniable, so when a host of invasive species targeting it began to appear, conservationists, cultural practitioners and community members sounded the alarm. You can help, too. Here are three invasive species that are threatening mamaki:
Originally discovered in 2018 in Olowalu Valley, the ramie moth’s presence on Maui (and now Hawai’i island) represents the first record of this species in the United States. The larvae can grow up to 10 centimeters, or about 4 inches, in length, and are a vibrant yellow and black with bright orange-red spots, a black head and thin white hairs. They may be seen feeding on a mamaki plant next to the larvae of the native Kamehameha butterfly, which do not have bright red spots on their side and possess thick, short spines on their bodies as opposed to the thin, long white hair of ramie moth larvae. Unlike the Kamehameha butterfly larvae, ramie moth larvae are aggressive, and if threatened, will rear up their head, thrash around and even hiss and spit. If left unmanaged, ramie moth larvae will completely strip mamaki leaves, leaving only the thick veins of the plant behind. Ramie moths and their larvae have been observed in forests and residential areas and are now being observed in commercial mamaki farms.
Mamaki rust (Pucciniastrum boehmeriae) was first discovered on Hawaii island in 2013. The rust attacks mamaki and other members of the Urticaceae family by causing the leaves to drop early. Since the initial discovery, surveys at nurseries and botanical gardens throughout the state found no other cases, however, the rust is widespread in the Waianae mountains and especially affects opuhe, another member of the native nettle family. At this time, mamaki rust has not been found on Maui, and cases should be reported if encountered.
Polyphagous shot hole borer
This tiny beetle is a little more than half the length of a grain of rice and has a reciprocal relationship with a fungus that it carries on its body. The polyphagous shot hole borer, or PSHB, damages mamaki by boring tunnels into the plant’s bark to farm its fungus food source. Although known to frequent more than 30 other plant species, in Hawaii, PSHB seems to prefer mamaki and opuhe, both members of the nettle family. Although little is still known about this beetle, it seems to prefer mamaki that are injured, reducing the plant’s chance of recovery by attacking it. Only documented on Hawaii island and Oahu, PSHB are difficult to spot and capture, but can be detected by the sawdust-like frass it leaves at the base of the tree or the tubes outside of its tunnels. They sometimes come out of their tunnels in the afternoon and, if spotted, should be quickly captured for identification.
With the eyes and ears of our community, we can all protect Hawaii from invasive species. Kilo (observe) the mamaki plants you frequent, whether they are in your backyard or along a favorite hiking trail, and report any suspicious pests to www.643pest.org.
* Serena Fukushima is the public relations and education specialist for the Maui Invasive Species Committee. She holds a bachelor’s degree in environmental studies and a graduate degree in education from the University of Hawaii at Manoa. “Kia’i Moku, Guarding the Island” is written by the Maui Invasive Species Committee to provide information on protecting the island from invasive plants and animals that threaten our islands’ environment, economy and quality of life.