Year in, year out, for centuries, the state’s beech trees have fed the animals of the wild world — squirrels, turkey, blue jays, woodpeckers, deer, and black bear. Its genus name “Fagus’’ comes from a Greek word, Fagito, meaning “to eat.”

Now a new threat to those trees — a vitally important part of the state’s forest ecosystem — has stepped across the threshold and entered our house.

The Connecticut Agricultural Extension Station announced this month that its researchers have found beech trees afflicted with a new disease — beech leaf disease — in Greenwich, New Canaan and Stamford.

It may be elsewhere.

Robert Marra, a forest pathologist at the station, said it lacks the staff to do a full survey of the state’s woods. It’s asking arborists and hikers to be on the lookout for the tell-tale signs of the disease — beech leaves with dark stripes between their veins, best seen from looking at the tree canopy from below.

Anyone who does see such leaves should contact Marra at Robert.Marra@ct.gov, or James Lamondia, the station’s chief scientist in plant pathology, at James.LaMondia@ct.gov

Area arborists were dismayed by the announcement, particularly because a non-native invasive species of nematode — a microscopic roundworm — seems to be the cause of the disease. It’s the first time that nematodes have been connected to a leaf disease in a forest tree in the US.

“Nematodes in a hardwood?” said Robert Gambino of Northeast Tree Pond and Turf Services in New Milford. “That’s a killer.”

“It’s bad news,” said Matt Bartelme of Barts Tree Service in Danbury.

Jeff Borek, an arborist from Sherman, said there are many different species of nematodes — some destructive, some beneficial — in the soil.

“I’ve never heard of one above ground,” Borek said. “It’s a whole new battleground.”

Researchers identified beech leaf disease in Ohio in 2012. It has since spread to Ontario, Pennsylvania and in Westchester County and Long Island in New York.

Now it’s in Connecticut.

Marra said because the disease is so new, no one knows how the nematodes in question — a newly described insect Litylenchus crenatae, subspecies mccannii — got to the US or how the disease spreads.

But Marra said researchers have found that when they look at even a small bit of infected leaf under a microscope, they can see hundreds of these destructive nematodes in the lab dish.

“It’s been a sort of leap-frog thing,” he said of the spread of the disease. “An insect or a bird that stops on a leaf could pick up the nematodes and carry them to a new tree. You only need one.”

Once the nematodes go to work, the striped leaves get leathery, curl, and drop off prematurely. Infected trees produce fewer leaves in subsequent years, as the nematode infestation increases.

The disease can denude and kill a beech sapling in two to five years. It can do the same to a fully-grown tree in five to seven years.

The agricultural experiment station said, at the moment, the nematodes seem to attack only native American beeches — Fagus grandifolia — and European beeches — Fagus sylvatica. Unfortunately, the latter would include the imposing copper beeches planted as ornamentals.

Beech trees are beautiful, with their smooth gray bark and rounded tree canopy. They’re shade tolerant, so they’ll thrive in an established woodland. Beech saplings grow out of the roots of mature trees, with a grove of trees spreading out from one parent.

They grow all along the eastern US from the Carolinas to Maine, in both southern oak-hickory woods and in northern maple-birch forests. Connecticut is a mix of southern and northern forests, so people can find beeches growing along the Long Island coast as well as the Northwest Hills.

Their nut crops feed the animals that live in the woods. Marra said that unlike oaks — which can rain acorns one year and produce few the next — beech trees are fairly consistent in their production of beech nuts. They’ve served the world well.

But beeches are already under attack from a bark disease, caused by a combination of non-native insects and fungi. Beech leaf disease is a whole new worry.

It follows the damage done by invasive insects such as the emerald ash borer and the hemlock woolly adelgid — non-native insects that have damaged thousands of tree in the state. Climate change could bring more insects, more arboreal diseases in the years to come.

“Our forests seem to be under continual assault,” Marra said.

Connecticut Media Group