Maui No Ka ‘Oi MARCH–APRIL 2009 61

Saving theWiliwiliA tiny wasp from Tanzania may the last, best hope for one

of Hawai‘i’s most important native trees.

Story byShannon Wianecki

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Across the reddish-black shards ofan ancient South Maui lava flow, agroup treks hopefully behind twoHawai‘i State entomologists. In alldirections, orange-tinged wiliwilitrees grow out of the a‘a lava, theiroctopus-like limbs reaching into theblue sky. Here and there a scarletseed is lodged in the lava like abrilliant Easter egg.This is Pu‘u o Kali—once heralded

as the most spectacular example ofHawai‘i’s native dryland forest. Butthis remarkable forest is underattack: a tiny, alien gall wasp hasmoved in. Now, instead of thickgreen canopies, wasp-infested wili-wilis dangle a few deformed leavesfrom otherwise bare branches. Manytrees have died. Hoping to preventthe forest’s collapse, the scientistshave recruited what may seem anunlikely weapon: another wasp.No one knows how the gall wasp,

Quadrastichus erythrinae, got toHawai‘i—most likely it hitchhikedon luggage traveling from Taiwan.Its arrival spelled doom for allspecies in the Erythrina genus,including the native wiliwili andpopular landscaping trees, suchas African coral and the falsewiliwili that once served as awindbreak along island high-ways and farms.Without a natural predator

in the Islands, the gall waspspread quickly from tree totree, leaving behind a trail ofdevastation. It lays its eggs inleaf tissue, causing leaves toshrivel into gnarled gallsaround its developing larvae.At Pu‘u o Kali, the older

trees weep—literally. Withoutfunctional leaves, they can’ttranspire. White streaks downtheir trunks show where the

trees have tried to expel the trappedwater that’s rotting them from theinside out. Some of the largest trees,likely several hundred years old,have exploded under the pressure.Pausing at the base of a gall-wasted

wiliwili, Darcy Oishi, one of theState’s biocontrol experts, holds up avial containing Eurytoma erythrinaewasps. Yet another alien species, thiswasp was carefully reared in theState’s quarantine facilities. It’s ahighly specialized predator that feedsexclusively on Quadrastichus larvae.The onlookers—representatives

from theHawai‘iDepartment ofAgri-culture (HDOA), the State forestrydivision, Maui Invasive Species Com-mittee (MISC), and the AuwahiRestoration Group—collectively holdtheir breath as thirty Eurytomawasps emerge and begin landing ongalls. Cheers and hoots erupt fromthe group: “Go get ‘em!”With luck, this release signals the

resurrection of the wiliwili forest—agoal that many have been workingtoward heroically.

Wiliwili trees are the keystonespecies of Hawai‘i’s dryland forest, the

pillars that provide the ecosystem’sframework. “Wiliwili is crucial on thelava flow,” says research biologist ArtMedeiros, who manages conservationefforts at Pu‘u o Kali and Auwahiforest reserves. “It flushes the flowwith nitrogen once a year, preparingthe soil for other native plants, such as‘ilima, ‘awikiwiki, and hibiscus.”Medeiros adds, “Of all the forests

I’ve been to, a deep, thickwiliwili for-est is one of the most beautiful. Whenthe leaves are flush, or when they falland the porcelainlike barks are glow-ing . . . there is no more flashyecosystem in the Hawaiian Islands.”Each year in late summer, wiliwili

trees erupt in showers of crab-clawblossoms: iridescent green, ivory,coral, and red. After the flowersfade, curled seedpods emerge,bearing striking red seeds. Both theflowers and seeds are coveted by leimakers. Early Hawaiians used thewiliwili’s buoyant wood for surfboards,net floats, and canoe outriggers.Until the gall-wasp invasion, con-

servationists viewed the wiliwili asone of the few native plants stillthriving in modern Hawai‘i.

The wasp was first detect-ed on O‘ahu in April of 2005.Nonnative Erythrina speciesfell prey first; galls showedup on trees around Honolu-lu. In July, Maui’s residententomologist Mach Fukadaspotted galls on coral trees atQueen Ka‘ahumanu Shop-ping Center. Within a week,the Big Island and Kaua‘ireported that Quadrastichushad also reached their shores.Stunned biologists imme-

diately launched into action.Maui’s invasive-speciesexperts met with then-mayor Alan Arakawa to

62 www.mauimagazine.net

Photo: Masako Cordray

Spectacular blossoms arethe wiliwili's late-summer gift.

Maui No Ka ‘Oi MARCH–APRIL 2009 63

devise a strategy. The County agreedto release emergency funds andMISC led cooperative efforts toprune and mulch infected trees.Not much was known about the

gall wasp when it arrived in Hawai‘i.The species was new to science;i t had only been described inSingapore a fewmonths prior. Craft-ing an effective control plan for anunfamiliar pest proved difficult.“The gall wasp was moving too

quickly,” says Medeiros. “Nobodyknew this then, but it turned into aworldwide invasion.”Initially, biologists thought that

removing infected limbs might savethe trees and prevent the wasp fromspreading into pristine areas. Thatwasn’t the case. The gall waspsattacked the new growth ontrimmed trees even more vigorously.Pesticide treatments were tried, butthey were expensive and unfeasiblefor wilderness populations. Treeswere dying faster than anyone hadimagined, and arborists watched inhorror as the wasp marched from

residential neighborhoods into thenative forest.By October 2006, the last wiliwili

stand in remote Nu‘u had beenthoroughly infected. Newspaperheadlines read, “Efforts to controlerythrina gall wasps fail” and “Alienwasp may doom the wiliwili.”“I was pretty hopeless then,” says

Medeiros. The conservation commu-nity’s emphasis switched from savingtrees to preserving seeds. O‘ahu’s LyonArboretum agreed to store seeds inanticipation of the worst-case scenario:extinction. The crisis brought scores ofvolunteers out of the woodwork; theyhelped pluck seeds from lava plainsaroundMaui County, representing thewiliwili’s diverse genetic pool.Among the volunteers were some

spirited third graders from Montes-sori School of Maui. The studentsreacted passionately to a slideshowMedeiros had shared with their class.They committed to shucking seeds—all 90,000 collected onMaui—for stor-

M A L A M A ‘ A I N A

Photo: ShannonWianecki

Photo: Lissa Fox

Quadrastichuserythrinae photos:Michelle N.Tremblay

Infected leaf photo:Forest & Kim Starr

Arborists watched in horror

as the wasp marched from

residential neighborhoods

into the native forest.Left: Unable to process water without functional leaves, an ancient Pu‘u o Kali tree

has burst. Above: Seen in magnification, Quadrastichus pupae will become food for

the new predatory wasp. Left unchecked, Erythrina galls cripple the tree's ability

to transpire.

age at Lyon Arboretum. They wroteand performed a skit telling the wili-wili’s tale.“About halfway through, you get

goosebumps,” says Medeiros.One student reportedly told his

mother, “I feel sick today, but if Idon’t go to school, no one will pro-tect the wiliwilis.”Thankfully, the students weren’t

the only ones going to any lengthsfor the wiliwili.Just months after the gall wasp’s

arrival, in December 2005, HDOAexploratory entomologist MohsenRamadan traveled to Africa insearch of a possible predator. Hisresearch revealed that Tanzania hadthe world’s largest number ofErythrina species, and was most like-ly the source of both the Erythrinagall wasp and its natural enemy.“Natural enemies reduce the

numbers so you don’t see the exten-

64 www.mauimagazine.net

sive damage that we’re seeing here,”says Ramadan. “To find specificnatural enemies, you really have toexplore their native region.”Ramadan scoured the Tanzanian

countryside, traveling for twomonths on rickety buses with insectsamples in tow. “I was lucky enoughto find some galls similar to those wehad in Hawai‘i,” he says. “More than90 percent of the galls showed para-sitoids.” He dispatched samples backto Hawai‘i, where the parasitoidswere ident i f ied as Eurytomaerythinae, a predatory wasp that laysits eggs beside those of Quadrastichuserythinae. Eurytoma’s larvae hatchfirst, and devour their neighbors.HDOA performed comprehensive

tests to insure that Eurytoma would-n’t become a new pest. “We are ableto say that this insect is specificenough that it will not attack any-thing other than the Erythrina gallwasp,” says Ramadan. Eurytoma wasapproved for release last December.Plant Pest Control Manager Neil

Reimer calls biological control “theonly way to save the wiliwili inremote and forested areas.” Reimerhelped shepherd the project throughthe cumbersome permitting process.“Projects like this take about

three years, sometimes ten,” saysRamadan. “We did it really fast.”The newwasp won’t have it as easy

as the first wasp; many of the originalhost trees are gone. Still, Darcy Oishithinks Eurytoma has a good chance.“It will disperse as well as the gallwasp, maybe better, because it’s a lit-tle more robust, bigger.”Plus, HDOA is working on two

additional parasitoids collected byRamadan. “Testing is 80 percentcomplete on the third parasitoid,”says Oishi. “Everything indicates it’sa really good candidate.”Among the three predators,

Ramadan is confident that “we’ll beable to see what I saw in Africa: gallwasp present, but in very few num-bers, and trees that are healthy anddoing well.”

Not a moment too soon. Back atPu‘u o Kali, Medeiros estimates thatbetween 10 and 20 percent of the for-est’s 20,000 trees have died. Still, thenative Hawaiian tree has managed toresist the gall wasp better than theother Erythina species.“The wiliwili is a tough tree,” says

Fukada. “It will figure out how toget through this.”Thankfully, it has some pretty

tenacious folks watching its back.

Ramadan scoured the Tanzanian country-

side, traveling for two months on rickety

buses with insect samples in tow.

Above: Erica von Allmen gathers seeds for safekeeping at Lyon Arboretum. Volunteers collected more than 90,000 seeds. Remnants of Hawai‘i's most magnifi-cent dryland forest can still be found amidst kiawe trees in South Maui. Below: Wiliwilis will survive, thanks in part to Art Medeiros's restoration team. (That'sMedeiros up in the tree.)

Photos: Masako Cordray