Laurel wilt, an invasive tree-killing fungus, found on Long Island

An invasive fungal plant disease has been discovered on Long Island, its first appearance outside the South, the state Department of Environmental Conservation announced on Tuesday. Laurel wilt causes rapid death of plants in the laurel family such as sassafras and spicebush, which are important members of Long Island’s native forest communities.

The fungus, which is native to Southeast Asia and carried by redbay ambrosia beetles, was identified last month after a Northport resident sent a sample of a dying sassafras tree to the Cornell Cooperative Extension of Suffolk County. Cornell University’s Long Island Horticultural Research and Extension Center identified the fungus and the university’s Plant Disease Diagnostic Clinic confirmed the diagnosis.

"We were very surprised," said Margery Daughtrey, a Riverhead-based plant pathologist at Cornell University who cultured and identified the fungus. Until now, laurel wilt had spread only as far north as Kentucky and Virginia. "We weren't expecting it to leap like that." But "I eventually had to face the reality of what it had to be," she said.

Daughtrey speculated that the beetle was transported from some place in the South to Long Island in a dead sassafras tree cut for firewood.

The damage has now been found in Dix Hills, Hauppauge, St. James and Greenlawn as well as Northport. The beetles can advance 10-30 miles each year.

The DEC's surveys show the damage "appears to be concentrated in small patches spread across the landscape," a DEC spokesperson wrote in an email to Newsday. "But there is a lot of variation within those patches — some are severely impacted and some much less impacted."

Long Island's woodlands are already under stress from another tiny invasive insect, the southern pine beetle, which has devoured thousands of acres in Suffolk County's pine barrens, Newsday previously reported. 

"The detection of laurel wilt on Long Island marks a troubling new chapter in the spread of this invasive plant disease," DEC Commissioner Amanda Lefton said in a statement. "DEC is collaborating with our conservation partners to understand the extent of impacted trees, evaluate control options, and launch public outreach to increase awareness about laurel wilt and how to report it. " 

The fungus is spread when the redbay ambrosia beetles tunnel into the wood of a tree or shrub, carrying spores of the fungus with them. The 1/16-inch-long beetles first appeared in 2002 near Savannah, Georgia, according to the Center for Invasive Species Research at the University of California, Riverside. They most likely entered the United States in wood shipping crates or pallets, the center said. They soon spread through Georgia, South Carolina and Florida; in some areas they have killed 90% of redbays, Daughtrey said.

One obvious sign of an infestation is long strands of sawdust emerging from the trunk and branches of a tree, which are the feces of the beetles. The fungus also causes rapid wilting of the leaves and shortly after, the death of the plant.

Experts say that controlling an introduced species like the redbay ambrosia beetle and the fungus it carries is very difficult. When a pathogen has evolved along with native plants, the trees develop ways to fight back, said Karen Snover-Clift, director of Cornell’s Plant Disease Diagnostic Clinic.

"But when it’s an introduced species, it's something they've never seen before, so it really causes severe damage" she said. "Our trees, the sassafras and spice bush, are very susceptible to it, and it's lethal to them."

Those two species are fairly ubiquitous in the forests on Long Island and elsewhere in the Northeast, and they provide nesting sites and food for a variety of birds, mammals and moths and butterflies, including the spicebush swallowtail and Promethea silkmoth. "So it could cause a very devastating damage across the state," Snover-Clift added.

Once laurel wilt arrives, there is no effective treatment that can eradicate it, as it’s not practical or safe to use fungicides across many acres of woodland. "A chemical control method really is not a solution," Daughtrey said. "No one's going to drench the woods with chemicals."

"At present, we really have nothing other than careful sanitation and public education," Daughtrey said.

The best way to stop — or at least slow — the spread of laurel wilt is to not move any wood, especially host species like sassafras and spicebush — from affected areas.

If landowners suspect an infestation on their property, experts stress that they should contact Cornell's Plant Disease Diagnostic Clinic for identification and instructions on safe disposal. "We want people to let us know before they cut anything down, let us confirm that's what it is," Snover-Clift said.

Most important, wood from a tree that may be infested should not be put out for trash collection or taken off the property. After an infestation is confirmed, experts may advise the wood may be burned or mulched on site, or professionals may safely transport it to an approved disposal site.

Members of the public who believe they’ve seen signs of laurel wilt are also urged to report it to New York State’s invasive species database. 

Cornell University will hold an online information session for the public on Sept. 10 about detecting and managing laurel wilt.

"If we can catch it early, that's always really beneficial for us," Snover-Clift said.