Banyan falls prey to mysterious pest

A popular weeping banyan tree in Moana­lua Gardens is dying from an infestation of a pest that’s new to the islands but has quickly spread on Oahu, officials said.

The state Department of Agriculture has received reports of trees from Pearl City to downtown Hono­lulu infested with lobate lac scale, an insect believed to be native to Asia or Oceania capable of killing plants by feeding off their sap.

While the department declared Oahu infested with lobate lac scale, it has received no reports of the pest on the neighbor islands.

The insect, which has also been found in Florida, Cuba and the Bahamas, was first reported to the Department of Agriculture in October in the Moana­lua Gardens banyan, though it appears the tree might have been sick as early as mid-August, said John Philip "JP" Damon, owner of Moana­lua Gardens.

It is unknown from where or how the pest came to Hawaii, but the Agriculture Department believes it could have been here for as long as a year.

The pest has also been found in koa trees and hibiscus bushes on Oahu, said Darcy Oishi, an entomologist and biological control section chief for the Department of Agriculture.

The infested banyan tree, adjacent to the famous Hita­chi tree at Moana­lua Gardens, is believed to be 70 to 100 years old. It has been off-limits to visitors because it "poses a huge risk" of branches falling, Damon said. "The effects of the scale on the tree basically removed all the sap from it, killing it and making the branches brittle. Seventy-five percent of the tree is dead."

The banyan will be removed, he said.

The tree has been a popular picnic spot for visitors and for events at the park, offering a canopy that spans 75 to 100 feet.

Despite efforts to control the pest, "in a span of less than two months, the tree just dramatically declined," said Abner Undan, arborist with Trees of Hawaii, the company that maintains many of the trees at the park.

Lobate lac scale infests and feeds on small, leafy twigs and branches. It produces honeydew that causes black, sooty mold to grow all over the infested tree or plant. Severely infested trees and plants have been known to die.

Young scale, called crawlers, are mobile and are often spread to other trees and plants by air and when plants are moved. Adult scales do not move, inhabiting the same tree until death.

After consultation with The Outdoor Circle, an environmental nonprofit, and members of the Aloha Arborist Association, Damon said it seemed like the best thing to do was remove the tree.

"I think it’s a consensus on all our parts that the tree would be so horribly disfigured after everything (dead) is removed from it that it wouldn’t be worth keeping, and there’s no guarantee that it would be able to sustain itself," he said. "I don’t like removing anything from the gardens if possible, but we put forth the best effort to do whatever we could to save it. This is just one of those situations where the victim is not going to survive."

Crews are scheduled to begin removing the tree Wednesday; it will take a few days to complete the job. Damon said after the tree is removed, the root system will be taken out, and the park will consider planting a replacement tree there.

The weeping banyan is the only tree at the park found to be infested by the scale, and it is not believed that any other trees at the park are susceptible to the pest, Damon said.

He said the Hita­chi tree — so called because electronics maker Hita­chi Ltd. is paying $4 million over 10 years to use the famous monkeypod tree in its advertising — is healthy and has not been affected, despite its close proximity to the dying banyan.

Lobate lac scale poses a number of concerns in the islands because not much research has been done on it, its origin is unknown and there are few known ways to effectively control it, officials said.

It was a major pest in Florida for a number of years, affecting more than 300 species of trees and plants, Oishi said. "They don’t know why, but there are very little (lobate lac scale) insects or disease now (in Florida). It just became background noise."

Though some pesticides have been found to be effective against the pest, Oishi said biological control — using a predator to control the pest population — is probably the most viable long-term control method, so it is necessary to find the scale’s origin. "But that might be years down the line," he said.

The Department of Agriculture, Damon and others involved are also concerned that the pest could spread.

"It’s already been found on koa," Oishi said. "We’re really worried about keystone native species, and if it does pose a problem to those species, we need to be able to control the pests in potentially remote and difficult-to-access areas.

"We’re hoping it follows Florida’s model where they had a problem and it kind of disappeared over time, but there might be slight genetic variances that make it more aggressive here and any number of other factors might be at play because we don’t know where we got it from."

Said Damon, "The main focus right now is to make sure it doesn’t happen anywhere else, to any other species. If that gets into the rain forest, if it’s unleashed there, there’s going to be hell to pay."