BEAUTIFUL AND BESIEGED: Princeton’s beech trees are being threatened with a new beech leaf disease caused by tiny worms called nematodes, which can destroy a tree in less than 10 years. Local arborists and residents are seeking the best ways to combat beech leaf disease. (Shutterstock)

By Donald Gilpin

Just 10 years since the emerald ash borer was first detected in New Jersey, and then proceeded to decimate many thousands of the state’s ash trees, a new threat, beech leaf disease, caused by tiny worms called nematodes spread by birds or the wind, has arrived and is likely to take a devastating toll on the area’s beech trees.

Princeton Municipal Arborist Taylor Sapudar reports sightings on private properties throughout Princeton and in Princeton Open Space. He has heard from private tree care companies that are trying to manage and treat the disease, but he cautions that “it’s still in the early stages,” and a number of questions about the origins and the most effective countermeasures remain unanswered.

“Staff will be monitoring the disease in the open space areas,” Sapudar said.

In a May 22 letter to Town Topics, naturalist and Friends of Herrontown Woods President Steve Hiltner warned that “Over the next 10 years, Princeton appears fated to lose nearly all of its beech trees.” He went on to note that the tiny nematodes “overwinter in the beech’s long coppery buds, causing contortions and curious stripping in the emerging leaves.”

He had first spotted the contorted leaves earlier in May in Herrontown Woods, heard that Mountain Lakes was also affected, and had noted that in Autumn Hill Reservation nearly all beech trees were suffering from contorted leaves and thinning crowns.

Since first being detected in 2012 in Ohio, beech leaf disease has spread to 12 states and the province of Ontario, Canada, including New York, New Jersey, and Pennsylvania, as well as all New England states except Vermont. The nematodes are thought to be not native to North America.

The Connecticut Agricultural Experiment Station reports that in Ohio researchers are seeing some American beech trees die within six to 10 years of infection while in the Northeast there is a faster progression of disease and decline with some trees expected to die in as little as four years after the first appearance of symptoms.

In an email Hiltner suggested two possible treatment options: “fluopyram, which appears to be too toxic to use widely, and various forms of phosphite, which is applied to the soil as a biostimulant that improves the tree’s immune system response.”

Hiltner quotes from The Holden Arboretum in Ohio website, which describes fluopyram as “a harsh chemical and its application should be considered with great caution.” The description continues, “The pesticide may kill all fungi in the application area, therefore we currently only recommend its use by professionals and in special cases.”

Phosphites, applied to the soil for uptake through the roots, “may provide some level of BLD control, although results can vary considerably,” according to a University of Massachusetts at Amherst website. “A notable improvement in tree vigor may take several years of regular treatments.”

Sapudar also notes positive effects from the application of phosphites, but states that there is no “cure” for beech leaf disease. “I’d also suggest a root biostimulant with humic acid in the summer months to offset stress. The phosphite triggers the tree’s natural defense mechanism to help against this pathogen.”

If residents suspect they have a tree with beech leaf disease, Sapudar recommends that they work with a private arborist on managing the disease. The arborist should be a New Jersey Licensed Tree Expert and should have a certification from the International Society of Arboriculture, Sapudar added.

Hiltner is not optimistic about the future for Princeton’s beech trees. In his letter to Town Topics he questions, “Where is science when we need it?” But he does see some hope in the phosphite treatments and in the fact that there are some beeches that seem to be resistant to the disease.

In his Princeton Nature Notes at princetonnaturenotes.org, he writes, “I encourage people to visit favorite beech forests in the area sooner rather than later to appreciate the now threatened beauty of this singular tree. Over the next few years, if you are fortunate enough to find one that remains healthy while others around it succumb, you should let people know. The Holden Arboretum site provides someone to contact.”