Invasive species have been impacting forests in Ontario for decades, with trees like beech often being forced to manage multiple threats at once. Stress from species like beech bark disease and spongy moth have already threatened beech tree growth and survival in parts of the province, and a relatively new threat, known as beech leaf disease, can put these trees at further risk of mortality.
What is beech leaf disease?
Beech leaf disease is a foliar disease that primarily affects American beech of all ages, though European, Chinese, and oriental beech have also been impacted. The disease is thought to be caused by an invasive nematode known as Litylenchus crenatae ssp. Mccannii (Lcm), which invades beech buds in the summer and fall, causing foliar damage that’s noticeable in the spring as leaves emerge. Infected, symptomatic trees will have dark interveinal banding on the leaves, making foliage appear striped or mottled. This distinct banding pattern can vary in colour depending on the time of year, sometimes appearing red during the spring and darker green in the summer. In severe cases, infected leaves can turn yellow and even become thick, leathery, and curled, eventually causing premature leaf drop. This damage limits a trees ability to photosynthesize, which reduces energy production and weakens the tree’s defenses.
Where has it been found?
Beech leaf disease was confirmed in North America for the first time in 2012 after infected trees were discovered in Lake County, Ohio. The disease has spread rapidly since its initial detection and can now be found in 12 other U.S States, including Michigan, Pennsylvania, and New York. BLD reached Elgin County, Ontario in 2017 and has been spreading along the shores of Lake Erie and Lake Ontario ever since.
What can we do?
Beech leaf disease is a relatively new forest invasive in North America, so there are still unanswered questions that need to be explored. For example, there’s a lot of ongoing research to better understand the pathways of spread, risk factors, and effective management. That said, there are still some general recommendations to limit BLD movement:
- Inspect beech trees regularly for any signs of beech leaf disease. Looking up at the canopy as the sun shines down through the leaves is an easy way to spot the interveinal banding!
- Report any signs of beech leaf disease to EDDMapS.org. These reports are sent directly to experts and researchers.
- Clean boots and equipment when leaving beech forests to prevent nematode spread.
- Stay connected for future events. The Invasive Species Centre will be hosting educational workshops on identifying and monitoring beech leaf disease as part of our new BLD Monitoring Network. This program is designed to increase early detection of BLD by recruiting community scientists that monitor and report local sightings. Our first event to kickstart the program will be in Barrie, Ontario on August 7, 2024 – click here for more details!
Interested in learning more? Check out the Invasive Species Centre’s BLD species profile for more information.
