by Felix Gonzalez
The American Beech Tree, Fagus grandifolia, is a native deciduous tree found abundantly in New York and the surrounding areas of the Northeastern United States. The native range of American Beech encompasses a portion of North America ranging from Illinois, south to Georgia, and north to Nova Scotia. The trees are commonly admired for their smooth grey bark and easily recognizable appearance thanks to their wide canopies and golden-yellow hue when changing colors during the fall seasons. These beautiful native trees are quickly becoming infected with a new disease known as Beech Leaf Disease (BLD). BLD threatens to clear large portions of beech tree populations in the forest of the Northeast, ranging from Ohio to New York.
What is this Beech Leaf Disease?
First discovered in Ohio in 2012, BLD is a threat to beech trees resulting in the gradual loss of leaves among infected trees. It is associated with an invasive foliar nematode, Litylenchus crenatae, feeding on beech trees, re-sulting in specific symptoms appearing on the leaves of the infected trees. These symptoms include dark banding of leaves, early leaf drop, thinning canopies, and curled leaves. Over time, these symptoms will lead to tree mortality and can occur 6-10 years after the initial infection. Mortality occurs due to the tree’s inability to produce enough nutrients to sustain itself through the course of the infection. The lack of nutrients is believed to be caused by the feeding nematodes gradually increasing in numbers and causing damage to the internal structure of the leaves. When damaged, the chloroplasts within the leaves are unable to photosynthesize properly, reducing the amount of nutrients the beech trees are able to create. In some stands, when the sugar reserves of the trees are depleted, root sprouts are developed from the main tree in an attempt to create more leaves for photosynthesis. However, this new growth uses more of the reserved nutri-ents and can potentially increase the speed in which mortality occurs. Much more information still needs to be collected to understand how we can prevent this outcome or delay it.
It has recently been discovered that BLD can not only infect our native populations, but also ornamental species like the European Beech, Fagus sylvatica, and its cultivated varieties commonly found in gardens and golf courses where their reddish-purple hue adds to the seasonal aesthetic. The only exception at the moment is the Japanese Beech, Fagus crenata, which appears to have developed its own resistance to the nematodes and displays only mild symptoms that do not result in tree mortality.
What is being done to control BLD?
Much more information is required to fully understand this new disease and how it spreads from tree to tree and region to region. Despite having only been discovered in 2012, BLD and the associated nematodes have made their way through the forests of Westchester County and New York State. Early detection is difficult as the leaves do not display symptoms of infection during their first year. Along with the delay of symptoms, the symptomatic leaves do not show signs of progression in severity until the following spring. This rapid spread has garnered concern among conservationists and environmentalists due to the widespread mortality expected in the coming years. Many forested areas of New York State are comprised of approximately 25% American Beech trees. Widespread infection throughout the state could result in the loss of a massive portion of the state’s forest. Various treatment options are being experimented with, but few have showed promising and effective results. With the help of citizen science and data collection by conservation based organizations, municipalities, and state agencies, more information can help to determine the best possible approach to treating infected trees, preventing the spread of infection, and identifying candidate stands for plantings.