Beech Leaf Disease

By Jade Greene 

Beech leaf disease is rapidly spreading through our region and is causing significant decline and death in beech trees. Learn more about this emerging threat to our forests and how you can help protect local trees.

About Beech Trees

Beech trees make up a significant portion of Bucks County’s forests, with the American beech (Fagus grandifolia) being the most common species. These  trees are easily recognized by their smooth, gray bark and their habit of holding onto their leaves throughout the winter. Mature beeches can soar over 100 feet tall and live for more than 200 years. Their nutritious beechnuts, rich in fat and protein, provide an important food source for squirrels, chipmunks,  birds, and even hungry humans. Beech trees also serve as the host plant for Early Hairstreak caterpillars. Beyond their ecological value, they are simply a beautiful and iconic presence in our local woodlands.

What is Beech Leaf Disease? 

Beech Leaf Disease (BLD) is caused by microscopic nematodes, tiny flat worms that live inside beech trees and feed on their developing leaf buds. When the leaves emerge in spring, the nematodes’ feeding damage causes them to be deformed and unable to function properly. Over time, the tree’s canopy thins and its ability to photosynthesize declines, eventually leading to death.

Young trees and saplings often die within two years of infection, while mature trees typically decline over seven to ten years. The disease impacts both native and European beech trees.

The nematodes that cause BLD are spread naturally through wind, rain, and wildlife. They can also be spread via firewood and nurseries selling infected trees to new areas. Unfortunately, BLD is now widespread throughout Bucks County and is present in every county in Pennsylvania.

How to tell if a tree has beech leaf disease?

Trees infected with BLD have a distinct banding or stripes on their leaves (see photos below). Later into the infection, leaves will look leathery and shriveled, you can also see a thinning in the canopy. 

Photos of trees infected with BLD, from Penn State Extension 

Can I manage beech leaf disease? 

Tree has port installed to deliver treatment for BLD

Research is ongoing for best treatment options for BLD. It is a challenging problem as it must be treated tree by tree, like ash trees, there is no way to treat an entire forested area. Penn State currently outlines these management options:

• Injection of nematode/fungicide into the tree trunk (best applied in June-September)
• Foliar applications of fungicides  
• Soil treatments of phosphite fertilizers to help boost a tree’s natural defenses

The life cycle of the nematode is going dormant for winter, so now is a good time to think about how to tackle this issue. Contact your Penn State Extension, DCNR Service Forester, and your local arborist to figure out a plan for your property. Let’s work together to save the beech trees!

Sources & further reading: 

https://extension.psu.edu/guide-to-beech-leaf-disease-for-the-public