Volunteers and paid crews across the state are fighting the aggressive forest weed miconia by hand, but researchers said they're making progress in finding biological agents that can help take up some of the workload.

They include fungi that kill leaves, stem-boring nematodes that kill branches, and bugs that eat leaves and flowers.

Only one of those has been released into the wild — a leaf fungus — and it shows promise, but won't control the weed alone. The others are undergoing extensive testing to ensure they attack what they're supposed to attack, and not native or commercially important plants.

Everyone's favorite example of biological control gone bad is the mongoose. Brought in by the sugar industry to attack rats that were eating cane, they immediately went after domestic fowl and native birds alike. It turns out mongooses mainly feed in daylight, and rats mainly come out at night.

Another example: Cattle egrets were brought in to control hide-scarring flies on cattle, but they quickly went on to other prey, such as shrimp in aquaculture ponds and pheasant chicks in hunting areas.

But modern biological control seeks extremely well-targeted agents, which are tested across hundreds of valued plants to be sure they'll stay on target.

"Biological control works 24 hours a day, seven days a week, and if we do the testing right, it's very specific," said Christy Martin, who runs the Coordinating Group on Alien Pest Species.

"We don't have lantana or opuntia cactus spreading across the countryside. That's an example of a suite of biological agents at work," she said.

RIGOROUS TESTING

Among the state's biological control experts is Eloise Killgore, plant pathologist with the state Department of Health's biological control sector. She said the testing is rigorous to make sure biological control stays on the species it's supposed to control.

"I test as many plants as I can per species, and I repeat tests," Killgore said.

The state in 1997 released a fungus, a variety of Colletotrichum gloeosporioides, which attacks miconia leaves. Its most impressive performance is on seedlings, where it can cause the young leaves to fall off and the seedlings to die.

Killgore said it appears to be surviving and working in areas where stands of miconia are dense, as in Onomea on the Big Island, but not so well in places such as Maui, where human teams are clearing weedy patches, and denying the fungus a reservoir of miconia plants on which to live, and from which to spread.

"It needs miconia to survive," she said. The state helped out Tahiti, where miconia is a massive pest, by bringing the fungus there in 2000. It's doing an even better job there than here, Killgore said.

"The fungus is doing a better biocontrol job there, having more noticeable effects because of the dense miconia population there and the wet, humid environment that the fungus thrives in," she said.

But as with some other pests, just one control measure is unlikely to be sufficient. Killgore is also working with a miconia fungus that does better in dry weather, and with a burrowing insect called a nematode that damages the stems, causing branches to die.

At the U.S. Forest Service's quarantine facility at Kilauea, a dozen insect predators of miconia are being tested by insect expert Tracy Johnson of the Institute of Pacific Islands Forestry's Pacific Southwest Research Station.

MICONIA MUNCHERS

Most of the fungi and insect pests of miconia come from South America and Costa Rica, where the plant, with its huge leaves with attractive purple undersides, is native.

Among the creatures are ones that feed on leaves and other parts of the plants as adults, and ones — sometimes the same bugs — whose larvae feed on leaves, flowers or internal tissues of the miconia plant.

One of the benefits of working with miconia is that it's part of a group of related plants, the melastomes, virtually all of which are pests, like its cousin the forest pest clidemia.

There are no native Hawaiian melastomes. That's fortunate, because it makes it highly unlikely that a bug that specifically attacks miconia — even if it were to wander onto another plant — would find a native plant it likes. More likely if it did move, it would just move onto another melastome.

For instance, Killgore found that the nematode she's testing also eats clidemia. She was pleased to find that it will not inhabit 'ohi'a, a more distant relative of melastomes, and one of the most important plants of the wet Hawaiian forest.

'2 TO 3 YEARS' AWAY

Among the frustrations for the biocontrol folks is that some of the pests look like they'd be useful, but they're too fragile. Johnson has a butterfly whose larvae are devastating to miconia leaves, but the butterfly is very difficult to raise in captivity.

"I'm hoping to find something that is robust and fast-spreading, and we're looking at a variety of agents," Johnson said.

The process of releasing an agent takes years. First the bugs and diseases need to be located in their home terrain, then government approvals are needed to import them under quarantine conditions. It takes a year or more of laboratory testing under strict quarantine conditions at special labs.

And then it can take another year to get government approval for release.

For the latest batch of anti-miconia critters, nothing's going to be happening real soon.

"We're probably two to three years from the first release," Johnson said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.