Beech Leaf Disease has spread across Ohio, into Northwestern Pennsylvania, Southwestern New York and Long Island, Southwestern Connecticut, as well as the northern shore of Lake Erie in Ontario, Canada.
Beech trees are already under threat from beech bark disease (BBD). And recently discovered in southwestern New York is another disease affecting beech trees known as beech leaf disease (BLD). BLD was first discovered in North America in Lake County, Ohio in 2012. It has since spread across Ohio, into Northwestern Pennsylvania, Southwestern New York and Long Island, Southwestern Connecticut, as well as the northern shore of Lake Erie in Ontario, Canada.
More research to better understand how BLD is caused and how it spreads is ongoing, but it behaves much like an invasive forest pathogen, spreading rapidly and causing significant ecological and economic damage. A nematode was discovered by Ohio Department of Agriculture, and in 2017 a Japanese research group described this new species of nematode, Litylenchus crenatae. It is thought by some researchers that BLD is caused by this nematode or a very similar species. Studies of other disease agents that could cause or have involvement in BLD are also being conducted.
Early symptoms of BLD include striping or darkening of bands between the leaf veins and reduced leaf size. The darkened area is thicker and slightly raised compared to the rest of the leaf tissue. As the disease progresses the striping and thickening become heavier, there is reduced bud and leaf production, and leaves near the branch tips become deformed and shriveled. Reduced bud and leaf production lead to loss of canopy cover. The disease progression varies based on tree size. In larger trees, disease progression is slower, beginning in the lower branches of the tree and moving upward. The disease also appears to spread faster between beech trees that are growing in clone clusters, as it is able to spread through their connected root systems. Most mortality occurs in saplings within 2-5 years. Where established, BLD mortality of sapling-sized trees can reach more than 90%.
The presence of beech bark disease (BBD), caused by a combination of bark and vascular tissue damage by the beech scale insect and the subsequent infection by several fungal species, which has been affecting American beech trees in New York State for decades, leads to root suckering and basal sprouting when an infected tree begins to decline. This can cause a dense understory of beech saplings that have ecological and timber production impacts, and has given beech trees somewhat of a bad reputation. However, beech trees are important economically, socially, and ecologically.
Beech are known as a foundational species, meaning that other organisms and overall functioning of the forest ecosystem depend upon these trees, and loss could therefore significantly impact other species.
Beech trees provide wildlife with food and habitat, such as beech nuts for turkey and black bears, dens for small mammals, and cavity nests for woodpeckers and songbirds. Additionally, loss of canopy cover would alter the shade provided by beech and modify light levels on the forest floor. This could cause change to species composition, forest structure, and expose areas to potential introduction of invasive species. Loss of beech leaf litter on the forest floor could lead to changes in nutrient cycling, soil moisture, and reduce nesting material, hiding places and protected spots for small mammals, reptiles, amphibians, and insects. Although BLD is unlikely to cause extinction of American beech trees, it could cause functional extinction of the species, meaning the reduced population will no longer play a significant role in ecosystem functioning.
Beech trees are not only a component of the deciduous forest, they are commonly found in urban green spaces as well. We appreciate the shade they provide on a hot, sunny day and recognize them by their smooth gray trunks that have the appearance of giant elephant legs, and in which you often find the initials of lovers enclosed in a heart. In addition to the social losses from loss of beech trees, researchers in Ohio used a model to predict economic losses if half of the beech trees in the state were lost.
Ecosystem services, carbon sequestration, biodiversity maintenance, and aesthetic and recreational value that would be lost amounted to $225 million.
Until more is known about BLD and how to control it, helping prevent its spread is a practice we can engage in. Moving untreated firewood is one of the main ways invasive pests and diseases spread. Don’t move firewood more than 50 miles from its source. Keeping an eye out for symptoms of BLD is also a good way to help with early detection and rapid response. Striping of the leaves is most apparent when viewing from below and looking up into the canopy. If you find yourself standing underneath a beech tree and think that you see symptoms of BLD, email NYSDEC Forest Health at email@example.com or reach out to Laura Bailey at Cornell Cooperative Extension of Yates County at 315-536-5123 or firstname.lastname@example.org