Experts battle two new insects attacking Hawaii’s trees

Lobate lac scale

Hawaii’s giant Banyan trees are under attack, posing safety hazards at island parks, along streets, and even on military bases.

According to tree experts and researchers, the insects damaging the trees are relatively new to the state.

Arborist Steve Nimz is working with the city, state and military to battle two new enemies: the lobate lac scale, which look like bumps, and the stem-galling wasp.

No one knows exactly how they got here, but they were discovered over a year ago.

“It’s becoming a more larger (problem) than before,” Nimz said. “We’re getting a lot of invasive introduced insect problems in the state right now.”

According to Nimz, these insects have been attacking trees in areas like Kapiolani Park and Moanalua Gardens by destroying new stems and leaves.

“We’re trying different types of chemicals, injection systems,” he said.

Nimz said chemical injections into trees should be done every six to 12 months and can cost $200 to $1,500 per tree.

Arborists say the chemical injections are showing positive results. Trees at the National Memorial Cemetery of the Pacific are recovering from the chemical injections.

But because the treatment can be pricey, the problem is hard to fight.

Experts are hoping that insect populations level off, or a predator comes along that only attacks these pests, but the challenge is “finding a predator that will attack only that specific insect and not attack any of our other plants or insects that are positive ones,” Nimz said.

The Banyan isn’t the only type of tree these insects like. Scale were also found on mango trees, and, while they aren’t a big problem for mango trees right now, they could be later on.

Researchers at the University of Hawaii at Manoa are also treating trees on campus, because if they don’t, “I wouldn’t say they would die next morning or next week, but they will go bad,” said Zhi Qiang Cheng, UH Plant and Environmental Protection Sciences.

At least one has already died.

So far they’ve identified and treated 45 Banyan trees on campus with a pesticide, using a trunk injection system to try and prevent any further damage to the tree.

The two-year project started in July 2013 after a landscaping manager on the campus noticed a problem with the trees.

“They ask us to help them to come up with a plan to help, to protect those trees because we have 60 Chinese Banyan trees on campus. Pretty much all of them are infected,” Cheng said.

This battle is different than the one in 2005 when the gall wasp infected a number of Wiliwili trees.

Since then, the state launched a campaign to eradicate the wasp with a pesticide and a predator to help protect the trees.

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