Wiliwili (Erythrina sandwicensis) – Dodging a bullet


    In 2005, a tiny wasp from Africa was accidentally introduced to Hawai‘i. The Erythrina gall wasp (Quadrastichus erythrinae), no bigger than a grain of sand, attacks the leaves of both the native endemic wiliwili and introduced coral trees causing the leaves to deform and eventually fall off. Without healthy leaves for photosynthesis, thousands of wiliwili and coral trees have died since 2005.

    When it was realized that chemical or manual control of the gall wasp wasn’t very effective, hundreds of people began collecting thousands of wiliwili seeds for storage at Lyon Arboretum and other genetic safehouses. Meanwhile, the State Department of Agriculture (DOA) began its search for a biocontrol agent to counter the Erythrina gall wasp.

    In 2006, the DOA found a gall wasp assassin, another tiny wasp from Africa, Eurytoma erythrinae, that kills the larvae of the Erythrina gall wasp. After extensive testing to make certain the assassin wasp would only attack the gall wasp and not other native or important introduced insects, it was released in 2008 on Maui and later on O‘ahu.

    Since then the results have been dramatic. Wiliwili trees throughout the State rebounded, putting out fresh healthy leaves following the 2009 winter rains. Only time will tell how effective this little assassin will be in years to come but for now, it appears that this common and beautiful tree of Hawai‘i’s dry forests has dodged extinction’s bullet.