Wasp infestation prompts removal of banyan trees at McKinley High School

Work will begin Friday to remove six banyan trees on the front lawn of McKinley High School.

The state Department of Education says the trees have been significantly damaged by an island-wide infestation of gall wasps.

Four banyans were previously removed in early April as a safety precaution, along with seven more since 2006.

“After several unsuccessful attempts to eradicate the gall wasp infestation over the past decade, we’ve concluded this is our best option,” said Dann Carlson, assistant superintendent for school facilities. “We have worked closely with our partners at the state Department of Agriculture and determined that the damaged trees need to be removed before they become a safety hazard to our students.”

Gall wasps were first identified on campus in 2005, at the same time as a wider infestation of banyan and wiliwili trees around Oahu.

The wasps burrow into branches and lay eggs into young leaf and stem tissue. Upon hatching, wasp larvae prevent new leaves from growing and cut exit holes upon departing. Impacted trees quickly suffer a loss of growth and defoliation before dying.

Past attempts to save the impacted banyans used a different variety of wasp, Eurytoma erythrinae, a natural predator of gall wasps, and several chemical insecticide treatments. Neither solution was successful enough to save the impacted trees. Lobate lac scale insects were also found attacking the same banyans, creating further damage.

The trees will be replaced with golden trumpet (Tabebuia chrysantha) trees.

“The banyans will be replaced with golden trumpet trees, which are naturally resistant to gall wasps and lobate insects,” said principal Ron Okamura. “These trees will provide similar-sized canopies, shade, and a wonderful display of gold blooms every spring on our front lawn, which match McKinley’s school colors.”

Tree removal and planting of the first 10 replacements are expected to be completed by early August at a cost of approximately $19,000 for tree removal and $8,500 for planting. Access to the surrounding areas of the campus will be restricted during this time.

Further replacement trees will be installed in future phases.

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