A mysterious new disease is poised to devastate Maryland’s beech trees

Moving quietly but quickly, a parasite is spreading through Maryland’s forests and front yards. Over the next decade, it could devastate a beloved and long-established tree.

Much about beech leaf disease — a malady caused by a microscopic roundworm called a nematode — remains mysterious. Scientists don’t yet understand how it got here or how it has spread so widely.

But it’s clear the disease could kill off many of the region’s beech trees, a stately hardwood dominant in northeastern forests and cherished for its silver, parchment-like bark.

First detected outside Cleveland in 2012, beech leaf disease has marched through Appalachia and the northeastern United States ever since. The disease was only discovered in Maryland three years ago, but already it has spread to nearly every county in the state.

On a recent visit to Patapsco Valley State Park, arborist Bob Saylor found a deep forest dominated by beeches with leaves struggling to push out — a sign that the nematodes were taking their toll.

“It was kind of surreal,” said Saylor, a plant health care manager for the Owings Mills-based Carroll Tree Service. “Just seeing these big stands of beech that aren’t going to be there in five to 10 years.”

The rapid spread of beech leaf disease has attracted relatively little attention outside arborist and forestry circles. But those tracking the pathogen fear a slow-motion crisis that could rewrite the future of many Eastern U.S. ecosystems, winnowing an important species that for centuries has plucked the heartstrings of naturalists, poets and any star-crossed lovers with a pocketknife.

Although scientists point to a handful of methods to treat the disease, they haven’t found a way to stop it.

Nematodes worm their way into the buds of beeches in fall and winter, feeding on tissues that then produce emaciated leaves. As spring turns to summer, the roundworms develop before laying eggs in the next year’s buds. A cycle begins. Struggling to photosynthesize — the process that uses sunlight to convert water and carbon dioxide into food — many affected trees deplete their energy and eventually die.

The disease can kill a young beech in a matter of a few years, while more mature trees may die within a decade. One study at an Ohio arboretum found that nearly a third of trees that contracted the disease were dead within 10 years of infection.

At an August seminar hosted by Baltimore City Recreation and Parks officials, residents sought advice on how to protect beeches in their yards.

City forest ecologist Megan Carr outlined the treatments available — including one method that involves drilling holes to inject a fungicide into the base of trees — but said that none of these would be viable on a large scale for her agency, which manages more than 2,000 acres of forested parklands.

Many forests in the Baltimore area are under siege by invasive species, a problem officials fear will only get worse as a shrinking beech canopy opens more turf for non-native plants to claim. At the same time, the beech’s big boughs provide habitat for birds like the scarlet tanager and purple finch, Carr said, while its nuts offer food for squirrels, raccoons and even bears.

The losses will extend beyond the ecosystems themselves, Carr said. “I think of these beech trees as witnesses in the forest to centuries of human history.”

And in more ways than one, they are.

The beech’s soft bark has long served as a favorite tablet for people to inscribe initials, dates or hearts pierced by arrows. Even the tree’s name hints at its role as a recorder of history: The word “beech” shares roots with the Old English bōc, meaning book.

“O Rosalind, these trees shall be my books,” says the character Orlando in the Shakespeare comedy “As You Like It,” in a declaration generally taken to refer to beeches.

Other trees may grow higher or attain “moments of showier glory,” the naturalist Donald Culross Peattie wrote in a 1948 tribute in The Atlantic. “But, taken in all seasons and judged by all that makes a tree noble — strength combined with grace, balance, longevity, hardiness, health — the Beech is all that we want a tree to be.”

In Baltimore’s Druid Hill Park, beeches dominate the canopy, and many of their trunks are tattooed with personal etchings. One pair bears inscriptions dating to 1945 and 1951.

But the markings of disease were also evident in this grove one morning last week. From below, the leaves on some young beeches showed a dark banding pattern — an early sign of infection — while the foliage of an older beech was withered and looked almost burnt.

Dom Bello, a forest conservation inspector at the Montgomery County Planning Department, said he’s seen beech leaf disease across his inspection area in southwestern Montgomery County.

“With any property with a large beech tree population, I can pretty much guarantee that if I look long enough, I’m going to find symptoms on at least a couple of the trees,” he said.

Bello estimates there are more than 1 million beech trees in Montgomery County, but warned that saving many of them won’t be viable. If a homeowner has a favorite tree in their backyard, then there are options, he said.

But “is there a cost-effective way to treat an entire forested area where we have miles or acres of beech understory?” he asked. “I don’t know that that exists yet.”

Heather Disque, a forest entomologist with the Maryland Department of Agriculture, remembers an Ohio official first warning about the issue at a regional meeting in 2013, so it wasn’t a surprise when officials found it here a decade later.

Disque’s agency is testing treatment options at parks in Frederick and Cecil counties and collecting seeds that could one day help to repopulate the species. The outlook may be grim, Disque said, but she’s hopeful that “there’s science and time” enough to protect many trees.

It wouldn’t be the first major die-off of an important tree in this region.

For much of the country’s early history, chestnut was dominant in the eastern United States — until the accidental introduction of a chestnut-killing fungus in 1904. Three decades later, Dutch elm disease wiped out much of the country’s elms. Scientists in 2002 discovered the arrival of an Asian wood-boring beetle, the emerald ash borer, which has since driven the death or decline of tens of millions of ash trees nationwide.

Bob Marra, a Connecticut plant pathologist, is working to prevent those kinds of losses for the beech. In 2024 Marra took a research trip to Japan, where he believes the nematodes originated, and at a New Haven lab he and his team are studying how to mitigate the disease’s spread.

The Connecticut scientist is an avid proponent of a potassium phosphite fertilizer that he said could prove a relatively low-cost method for stimulating nematode resistance in large swaths of beeches, and he predicts that targeted treatment will save some of the region’s trees, preserving their genetic diversity.

Then one day, after the threat of nematodes has faded, Marra hopes the beech population can begin to return.

Ginny Bixby contributed reporting.