Wasps Threaten Maui's Wiliwili

In recent years, scientists have been trying to combat the spread of a species of non-native wasp that's killing the wiliwili. The wasp, which is called the Erythrina gall wasp, lays its eggs on the tree's leaves, which deforms the leaves and eventually kills the tree. While wiliwili are not a keystone species on Maui, they have long been valued by Hawaiians for their flowers, seeds, and wood.

This Landsat satellite image shows bright green, lush forests on Maui's northern, rainy slope and the drier, pinkish wiliwili forests to the south. The strips of pink pointing to the eastern coast of Maui are steep gullies thick with wiliwili.

Scientists believe the Erythrina gall wasp arrived in Hawaii in 2003 as a stowaway on a cargo ship from Taiwan. Its rapid spread eastward from Hahului Harbor was probably hastened by non-native wiliwili trees that were planted along the roads and agricultural areas on the island's neck. The line of non-native trees acted like "a burning fuse that went straight to the native forest," said Art Medeiros, a scientist with the U.S. Geological Survey Pacific Island Ecosystems Research Center.

To help stop the wasp from destroying Hawaii's treasured native forest, scientists are currently testing insecticides on the wasp and are investigating biological agents that appear to control the wasp in Africa.

--Bjorn Carey

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Credit: American Museum of Natural History