What You Need to Know About the Approaching Menace to Maryland Trees

Traditional symbols of strength and permanence, many large forest trees have begun to look remarkably vulnerable to the stresses of sharing the planet with humans—from climate change to invasive pests transported from one corner of the world to another. As many as 100 U.S tree species could be wiped out in the coming decades, scientists reported last year.

The latest threat has been marching across northeastern forests, killing one of the most common and abundant types of trees in our region. Beech leaf disease (BLD) devastates all species of beech trees, from ornamentals used in landscaping to those smooth-barked, 120-foot-tall behemoths that are a frequent canvas for people carving their initials.

University of Maryland Extension Agent Associate John Hooven has firsthand experience with BLD, surveying a forest that was hit with it in 2021 in Cortland County, New York. We recently sat down with him to get the facts about this new, still-mysterious disease and what it could mean for the state and region.

What is BLD?
Beach leaf disease is a foliar disease, meaning it affects the leaves of the tree, and it’s caused by a non-native nematode, which is a microscopic type of worm-like organism. It was first identified in Ohio in 2012, and has since spread across the Northeast. It’s been identified in 11 states and Ontario, Canada, and the consensus is that it’s in Maryland, based on observations in both Pennsylvania and Virginia. Maryland Department of Agriculture has been actively looking for it but has yet to identify it here.

How bad is it? Could it wipe out beech trees like Dutch elm disease did?
That seems to be a possibility, but there are still a lot of unknowns. It seems to impact young beech trees more than older ones, but both are affected, including very large trees. Mortality occurs within two to seven years, and there is no known remedy to date, no way to mitigate it. That’s concerning because it’s spreading rather fast for a tiny little nematode. There is the idea that it could be treated with some sort of spray, but in a forest setting, that’s not going to be practical.

What tactics are forest managers using to prevent or slow its spread?
At this point in time, we're just in an observe-and-report mode. Wherever it’s found, it’s good to get that information back to the researchers and the labs that are working on the issue. There are some trials going on in Ohio to investigate different treatment options such as the use of one chemical that can strengthen trees’ resistance to the disease or injecting insecticides directly into tree stems to kill the nematodes without hurting other insects.

How important are beech trees to Maryland forests?
Beech trees are very important to the whole region. They’re some of the most common trees in Maryland forests, and they can live for hundreds of years. They provide important habitat for birds and small animals, and their nuts are edible, so they provide food for species such as bear and other animals. Beech trees are also shade-tolerant, so most species will grow in established forests where other trees won't, which means they fill an important ecological role.

What can I do to protect my beech trees?
Since it’s still unknown how it’s being vectored, it’s very important not to move materials from potentially infected areas to uninfected areas. That includes any yard debris, firewood, leaves, soil, seedlings and things like that. Landowners with beech trees on their property should monitor their trees for the symptoms of the disease and avoid moving materials around their property.

How can I identify it?
What’s most identifiable about BLD is the banding between the veins of the leaves, especially when you are looking up into the canopy from below. If you’re looking at lower leaves, you can turn the leaf over and see it from the underside. You’ll see alternating dark green and light green stripes, and the leaves will look leathery and curled. Eventually, the leaves wilt, turn yellow and die.

What’s really important is that there is a look-alike, a native beech leaf rolling aphid that appears strikingly similar, but it’s native and doesn’t have an impact on the tree. The aphid causes yellowing and curling of the leaves, that can be mistaken for BLD. But it’s the banding, or striping of dark green and light green that indicates it’s BLD.

What should I do if I see it?
If you suspect beech leaf disease, you should report it to the Maryland Department of Agriculture’s Forest Pest unit by emailing them at fpm.mda@maryland.gov or call 410.841.5870.

MDA also recommends disinfecting your shoes with a solution of bleach and water immediately after walking through stands of infected trees, so if you think you’ve seen BLD, it would be good to take that extra precautionary step.

Is there anything else people should know about this disease?
Our society needs to do more about preventing the spread of invasive species. An ounce of prevention, as they say … . It is not sustainable to invest in control after a species invades. Humans are the No. 1 invasive species. It’s our responsibility, therefore, to steward the lands and prevent and correct the spread of invasive species across the landscape.