Workers Inject Trees to Protect Against Dutch Elm Disease on the Common

Nearly 130 American elm trees in the Boston Common had yellow caution tape around them Tuesday, as workers injected the trunks with pesticides to protect against Dutch elm disease.

"This is the highest concentration of elms in Massachusetts," said Jeff Kimball, an employee at tree care company Harney Greymont.

Actually, make that the largest cluster of elms in Eastern Massachusetts, added Henry Davis, an arborist for the Friends of the Public Garden. Every year the nonprofit pays about $75,000 to protect against the deadly fungus that wiped out many of the American elms in the 1940's and 1950's.

Keeping the trees from dying comes down to control and diligence said Kimball, as he positioned containers of beetle-killing poison around the trunk.

"I've been doing it for 30 years," he said. "But I'm no pioneer."

It takes about an hour for the tree to absorb the insecticide, which travels through the trunk and up into the branches, killing Dutch elm beetles when they start to feed. However, the trees need to have leaves to draw the sap - containing the insecticide - from the bottom to the top. So if they start feeding early, the beetles beat the tree preservationists to the punch.

"It's a battle here to get ahead of the beetle, and wait for the leaves to come up," said Davis, who has been working with the Friends of the Public Garden for the past 40 years.

Dutch elm disease also spreads through the roots from tree to tree, and can live for years in the soil, so having a large cluster like the one in the Common is rare, he said.

Thanks to the funds from the Friends of the Public Garden, and an ongoing dedication to care for the trees, the American elms stand tall in Boston.  Yet despite the annual precaution, there's always a few casualties.

"Last year we lost three in a row," said Kimball, pointing to a small clearing. "Beautiful trees."