Wednesday, January 15, 2014

Insect from down under attacking Hawaiian naio

An invasive insect from Australia by way of California is severely damaging one of Hawai`i`s prized native plants, the naio or false sandalwood.

The pest is a thrips, a class of tiny sucking insects that puncture plants and suck their fluids, and which in the process can disfigure and weaken the plants. The bug, Klambothrips myopori, only feeds on species of myoporum, of which naio is one.

(Image: The youngest leaves of the naio and severely disfigured by attacks from the alien thrips pest. Credit: Hawaii Department of Agriculture.)

So far, they are mainly on the Big Island, and naturalists are trying to control their spread.

The start of the Hawaiian naio dilemma is described in a2009 Hawai`i Department of Agriculture paper by Patrick Conant, Clyde K. Hirayama, Monica I. Lee, Cheryl L. Young, and Ronald A. Heu.

The authors note that Hawaiian naio’s young leaves are severely deformed by the thrips.

New Zealand ecologist Jon J. Sullivan outlines the problemin a paper in the journal Biological Invasions.

It all started long ago when a New Zealand relative of the naio, called ngaio in New Zealand and Myoporum laetum to science, was imported to California as an ornamental plant, and then escaped cultivation and became a weed. 

The thrips, a tiny, thin, black,winged insect, doesn’t occur in New Zealand, but does occur in Tasmania, an island south of the continent of Australia, on a different myoporum that presumably tolerates the pest. 

In 2005, the thrips showed up in California, and since then in rapid order it has killed off half the Myoporum laetum in California and has defoliated many of the rest. To Californians worried about the spread of the myoporum, it was considered an inadvertent but fortuitous form of biological control of a weed.

A University of California-Riverside Center for Invasive Species Research outlines the scope of the California problem.

Then in December 2008, it showed up on Hawai`i island. The Hawaiian Myoporum sandwicense is clearly susceptible to the thrips attack.

“Initial indications are that K. myopori populations are also starting a sustained outbreaking in Hawai`i on native, and presumably more genetically diverse, M. sandwicense, and plants are again being defoliated and killed,” Sullivan wrote, citing a report by the state Department of Land and Natural Resources.

The big problem in all this, Sullivan says, is national borders that are “leaky” to biological invasion.

“It is…hard to imagine how it could have been predicted that a previously unknown and uncommon Tasmanian insect would cause a mass dieback of a New Zealand native plant in California,” he said.

Or, for that matter, that the same insect would find a host among the native plants of Hawai`i. 

The Hawaiian naio attack continues and is growing, according to a paper, “Assessing the impacts of an invasive thrips (Klambothrips myopori) infestation on native Myoporum in Hawaii,” by Cynthia King, Robert Hauff, Leyla Kaufman and Mark Wright. They are with the state Division or Forestry and Wildlife and the University of Hawai`i-Manoa Department of Plant and Environmental Protection Sciences.

Scientists are hoping that natural enemies like small wasps, will help them gain control over the thrips expansion.

© Jan TenBruggencate 2014

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