Renowned for its smooth, light-gray bark and its large size, the American Beech is one the most easily recognized trees found in climax forests throughout the lower Susquehanna valley. Preferring rich soils, this shade tolerant native produces an abundance of nutritious nuts for wildlife including deer, turkey, grouse, squirrels, woodpeckers, and a variety of songbirds.
If you’ve visited a stand of beech trees lately, you may have noticed that the canopy seems a little sparse in comparison to the foliage of the oaks, poplars, and other hardwood species in the vicinity.
Sunlight reaching the forest floor through gaps in the canopy of American Beech trees.
A closer look reveals the cause. And yes, it’s big, big trouble.
Many newly emerged leaves on this American Beech are thickened and curling in comparison to apparently healthy leaves on the same branch. These sickly leaves are being afflicted by Beech Leaf Disease (BLD), the result of infection by a parasitic roundworm, Litylenchus crenatae mccannii, a microscopic nematode that reaches its greatest abundance within the victim’s new buds. After increasing their population density there during the summer and fall, the nematodes overwinter within the dormant buds, then cause progressive cell damage in the foliage that emerges during the spring to make the leaves appear “striped” before withering and falling away.Early season leaves on an American Beech perishing from infection by Litylenchus crenatae mccannii, the nematode responsible for Beech Leaf Disease. BLD also affects Oriental Beech (Fagus orientalis) and European Beech (F. sylvatica), both imported to North America for ornamental cultivation. BLD was first detected Lake County, Ohio, during 2012 and has already spread to every county in Pennsylvania and into much of the northeastern United States and neighboring portions of Canada. The nematode responsible for BLD possibly originated among F. orientalis stocks in Japan, but its exact origins remain unconfirmed.Cell damage from Litylenchus crenatae mccannii makes the new foliage on this American Beech appear “striped” before total deterioration.A sparse canopy in a stand of native American Beech trees being destroyed by the nematode, Litylenchus crenatae mccannii. Defoliation over a period of 5 to 8 years will probably prove fatal to trees of this size. Smaller trees may succumb in just 2 to 4 years. Other sources of stress such as the extended period of drought we recently experienced may hasten the demise of afflicted trees.
While treatment for BLD is possible, it must be done early. Protecting an entire stand in a forest can be prohibitively expensive, but if you have a specimen tree or small grove you think you might like to save, click here for a Penn State Extension guide with more information.
The Blackburnian Warbler, a Neotropical migrant, feeds high in the canopy of mature forests during stopovers in the Lower Susquehanna River Watershed, so you need to look up to find one. This male was seen searching for insects along the branches of an American Beech (Fagus grandifolia).
