HILO, Hawai'i — Plans are advancing to release an insect from Brazil on the Big Island to slow the spread of strawberry guava, known as one of the worst plant pests in the state.

If state and federal regulators agree, the project would mark the first time a natural enemy of strawberry guava has been deliberately released in Hawai'i to try to control the spread of the fruiting trees. It would also be the first time the scale-type insect has been released in the United States.

Earlier this month, the state Board of Agriculture approved an application for the scale to be considered for the list of insects that can be legally imported into Hawai'i, and for approval of conditions for the planned release of the insect on two parcels of state land on the Big Island.

Tracy Johnson, research entomologist with the U.S. Forest Service's Institute of Pacific Island Forestry, said he hopes to obtain additional approvals for the project from the state Department of Land and Natural Resources and the federal U.S. Department of Agriculture's Animal and Plant Health Inspection Service by the middle of next year.

That would clear the way for release of the insect, known by its scientific name, Tectococcus ovatus, on two of four parcels of state land researchers have been monitoring at the 3,000-foot elevations of Kilauea and Mauna Loa.

The four parcels are sprouting young strawberry guava plants, and each sits near the edge of the advance of the guava plant. Below the sites are areas where strawberry guava is thick, in some places choking out virtually all other plants. Above those elevations, the plant is less common, but it is advancing.

The release would be the result of 15 years of searching for a natural enemy of the strawberry guava, a plant that was introduced to Hawai'i in 1825 and spread rapidly in Hawai'i's rain forests. Also known as waiawi, it has no natural enemies here, and feral pigs eat its fruit and distribute seeds by the millions.

The scales aren't expected to kill the guava, but Johnson said the hope is that when the insects feed on the young trees, the plants will weaken to the point that they can't mature or fruit, which would stall the spread of the plant.

"What we're hoping it will do is slow down the growth of any plant it attacks," Johnson said.

The scales would be released on two sites, while the other sites with similar guava populations and growing conditions would be monitored for comparison, to determine how much of an impact the scales have, Johnson said.

The scales are native to Brazil, and the Forest Service already keeps a colony at a quarantine facility in the Hawai'i Volcanoes National Park. Researchers there have been testing the insect to make sure it will not feed on other plants such as commercial-grade guava or the native 'ohi'a trees.

They are now confident the scale will not hurt native forests or commercial crops, but don't know how quickly the scale will spread.

The eggs and newly hatched nymphs can be distributed by the wind, but scientists don't know how far or how quickly they will drift. The males can fly, but can't spread the species on their own, so researchers will watch to see how fast the scale can spread.

Scientists plan to monitor the test sites for five to 10 years, Johnson said.

Reach Kevin Dayton at kdayton@honoluluadvertiser.com.