Wiliwili - Threats

Threats

Like other indigenous species in Hawaiʻi, the wiliwili is threatened by competition with non-native species that are free of the diseases, parasites, and herbivores that constrain them in their original habitats.

It was reported in December 2005 that the Hawaiian wiliwili population was under immediate threat due to an infestation by a gall wasp, Quadrastichus erythrinae, which had been first reported in Hawaiʻi in April of that year. This invasive species appears to have arrived in Hawaiʻi via southern Taiwan, Singapore and southern China within only two years. This species was not known to science and was formally named and described in 2004. It is thought to have originated in Africa, and the means ot its rapid dispersal across South Asia, the Pacific, and southern North America is not understood. The majority of trees of introduced Erythrina species have died as a result of gall wasp infestation. Native wiliwili forests have also been hard hit, particularly Puʻu o Kali on the island of Maui-once considered the most pristine example of Hawaiʻi's dryland forest ecosystem.

A second wasp, Eurytoma erythrinae, was released by the Hawaiʻi Department of Agriculture in December 2008 as a biocontrol to minimize the damaging effects of Quadrastichus. Eurytoma wasps lay their eggs in the galls created by Quadrastichus wasps. Eurytoma larvae hatch faster than Quadrastichus larvae, on which they exclusively feed.