Scientists and foresters say the lack of public pressure has meant that the state has been slow to mount an adequate response. They are worried that the beetles will not only devastate the Pinelands, but will also eventually attack coastal pinelands on Long Island and Cape Cod.

In New Jersey, the beetles hit a peak in 2010, when they killed trees across 14,000 acres of state and private land. More recently, the damage has been a few thousand acres per year. But with the beetle now endemic in New Jersey, experts do not think that reprieve will last.

“I’m worried about when we really get a superstress on the trees,” said George L. Zimmermann, a forest ecologist at Richard Stockton College of New Jersey, in Galloway. “If the beetle takes off, you could be talking not tens of thousands of acres, but a hundred thousand or more.”

Historically, it was too cold for the beetles to live north of Delaware. In their native habitat in the South, they are always present at low levels, surviving by attacking diseased or weakened pine trees.

The beetles, no bigger than uncooked grains of rice, burrow through a tree’s bark and consume a layer of tissue that provides the tree with nutrients and water. As the evergreens starve to death, they take on the color of a broadleaf forest in autumn.

Healthy trees can fight off small numbers of beetles by exuding a sticky sap that pushes them out. But a large beetle outbreak can overwhelm even vigorous trees. “The way they kill trees is the way wolves kill a moose — they do it by numbers,” said Matthew P. Ayres, a Dartmouth biologist who studies the beetles.