NARS Commissioner Warns of Harm Thrips Could Cause to Naio

The pictures of dead roadside shrubs and tortured, shriveled leaves say it all: If introduced to Hawai`i, myoporum thrips could do to naio what erythrina gall wasps did to the state’s wiliwili trees.

At last March’s Natural Area Reserves System Commission meeting, commissioner Lloyd Loope distributed photos of the thrips and the damage they have caused on the mainland. The injuries to the affected trees look strikingly similar to the damage caused to Hawai`i’s wiliwili trees by the gall wasp. Since the discovery of the erythrina gall wasp’s presence here in 2005, the invasive insects have swept through the islands and killed thousands of native and non-native wiliwili trees faster than anyone could have imagined. Like the erythrina gall wasps, the thrips lay their eggs on the leaves of their hosts, producing galls that can slow growth or kill the plants.

“It just looks so similar to the erythrina gall wasp. It was discovered in 2005; it’s an invasive species of myoporum from New Zealand. In southern California, [myoporum] is planted by the thousands along roadsides and this thrip was discovered attacking them,” he said.

“The technical term is ‘déjà vu all over again,’” said commissioner Pat Conant, an entomologist with the state Department of Agriculture.

Worried that these thrips could harm Hawai`i’s naio (Myoporum sandwicense), which is an important native species often used in restoring degraded areas, Loope brought the matter to the NARS Commission to help spread the word, and perhaps, help encourage the state Board of Agriculture to enact rules to keep the tiny bugs out.

Last year, Loope did much the same to protect `ohi`a (Metrosideros polymorpha) – the most dominant tree in native Hawaiian forests – from a potentially devastating rust. His efforts eventually got the BOA to impose an interim ban on the importation of plants in the Myrtaceae family (which includes guava, eucalyptus, and `ohi`a) from California, Florida, and South America without proof that the plants are free of the rust, Puccinia psidii.

“That was real good. At the time we also had the idea that the Hawai`i Department of Agriculture should protect dominant native species as much as they have in the past protected sugarcane, pineapple, coffee and other things,” Loope told the commission, adding that so far, the DOA has not been enthusiastic about the idea.

Although there isn’t much naio on Maui, it’s found on Hawai`i from the coast all the way up the mountains, according to Hawai`i NARS manager Lisa Hadway.

Commissioner Jim Jacobi said that there are two distinct forms of naio, a sprawling coastal shrub and a rainforest tree, and because the sprawling form is common in the landscape trade, someone might want to bring in a cheaper source from outside the state. “That’s what scares me,” he said.

Conant added, “There is a sprawling form over there that gets infested but not quite as heavily as their upright form, but he’s got a good point. If someone says, ‘Oh man, I can have guys grow that in California for peanuts and bring it in in a Matson container,’ it’s all over.”

He added that the state needs a uniform plan to protect at least the six most dominant forest trees.

“This is a big issue because we’re going through this all over again to get yet another species regulated for one pest. Do we have to do this every time we see this happen or are we going to have a list of dominant forest trees for which we’ve already got restrictions in place?” he said.

Commission chair Dale Bonar suggested that the commission could write a letter of support to the DOA. In addition, commissioners recommended getting the U.S. Fish and Wildlife Service and conservation community, including the Hawai`i Conservation Alliance, behind the idea.

Across the street from Waianae High School sits a 19.5-acre lot covered mostly in bare dirt with patches of thick kiawe in parts. Beer bottles are left on the ground and plastic bags filled with household trash were at one time stuffed into the sinkholes scattered throughout the property.

Years ago, the state transferred the land to the City and County of Honolulu so that it could become a city park. But during a survey of the sinkholes, the city found `opae `ula (Halocaridina rubra) and another rare shrimp species, Metabetaeus lohena, which is a candidate for the federal endangered species list. The park project was put on hold, and at the urging of the state Department of Land and Natural Resources’ Division of Aquatic Resources, the state regained control of the property in January.

Now, a proposal is being drafted to designate the site as a NAR. Although it’s not a particularly pristine site, NARS staff pointed out in a presentation to the commission that it does support the rare shrimp and is geologically unique – the entire area is the site of an ancient reef whose geology is characterized by sedimentary rock instead of lava. What’s more, the U.S. Fish and Wildlife Service has indicated that it is willing to fence off certain sections of the sinkholes if the state decides it wants to protect the site.

At the commission meeting, NARS O`ahu branch manager Brent Lisemeyer expressed concerned about the management burden this new and unusual site would add and asked if his staff would be expected to try to enhance populations of the rare species there.

DAR administrator Dan Polhemus responded, “We want to keep the sinkholes so people aren’t using them as garbage dumps or luas [toilets].” Other than that, the site wouldn’t need any more management. He added that his own staff could assist NARS staff with managing the area.

— Teresa Dawson

Volume 18, Number 12 June 2008