Beech leaf disease (BLD) is an emerging disease caused by a nematode, or microscopic worm. We often don’t think of our trees as getting “sick.” However, just as people can contract diseases, trees can too. Some of these diseases have been present for centuries. Some are relatively new, or sometimes just new to a geographic region. Beech leaf disease is relatively new to North America. It was first discovered in 2012 in the Cleveland, Ohio area. Since that time, the disease has been spreading rapidly. It has now been confirmed in 11 states in the northeastern and midwestern U.S. as well as Ontario, Canada.
This is a devastating disease. Trees infected with the nematode can die as early as six years from when symptoms first appear. Over time, through study and research, we — and the entire arboricultural industry — have been learning more about the disease and how to treat it.
Trees at Risk of Infection
Beech trees are a common species in forests and landscapes across the eastern U.S. and Canada. The native American Beech is a prevalent host for beech leaf disease. Additionally, European and Asian beech varieties that have been added as landscape species are also at risk.
The microscopic worms, which feed on plant foliage, are thought to have been introduced from Southeast Asia, where they are likely endemic. The nematode does feed on Japanese beech in Japan with mild symptoms. Unfortunately, the impact is much more severe in North America.
Beech Leaf Disease Symptoms
Dark green stripes between the leaf veins are an early sign. Looking at the leaves from the top, they will begin to have a cupped or puckered appearance. These symptoms usually progress from the bottom of the canopy upward. Sometimes, though, you can see the effects scattered throughout the tree’s canopy.
After repeated years of infestation, nematode populations continue to grow. Accordingly, symptoms become more severe. Leaves become deformed and paler in color with a thickened, leather-like texture. At this point, the disease begins to limit photosynthetic capacity. Therefore, trees cannot produce the nutrients needed. The tree will begin to decline and buds begin to die. Eventually, the entire tree will die.
We are learning more about beech leaf disease. Recently, experimental data has demonstrated effective treatments with a product applied to beech trees in late summer. You should also try to keep your beech trees as healthy as possible. Minimize stress factors, irrigate properly and maintain healthy soil to keep up their natural defenses.