Signs of BLD include puckered, distorted leaves, with dark striping between the veins. (Courtesy images)
One of our favorite properties for a beautiful walk in Manchester-by-the-Sea is Coolidge Reservation. We are awed by this property with its scenic marshy pond and the trail that leads to the vast Ocean Lawn on Coolidge Point. In addition to the wide and spectacular views of Massachusetts Bay, the Ocean Lawn has numerous strikingly huge European Beech trees (Fagus sylvatica) with dense canopies that provide shade in the summer.
Sadly, this spring we noticed that these stately giants were looking quite ragged. Their leaves were distorted, and the foliage overall was thin, since many of the leaves had been shed.
Recently, the Director of Horticulture for Native Plant Trust, Uli Lorimer, informed us that Beech Leaf Disease (BLD) is the latest blight to threaten beeches, as they have already been weakened by Beech Bark Disease. BLD is caused by an invasive foliar nematode from the Pacific Rim. A foliar nematode is a worm-like organism. You can’t see it unless you look through a microscope. Typically. nematodes -- both helpful and not -- are found in soil but these live on the leaves. According to scientists at UMass, “prior to BLD, no foliar nematode was ever known to cause a disease of woody plants that results in mortality” (Carta el al. 2020). This fast-moving disease, probably transferred from tree to tree by birds and other wildlife, is devastating to all beech trees, including the American Beeches (Fagus grandifolia) found throughout the woods on Cape Ann.
So, what can we do? BLD was first identified in Ohio in 2012 and is now firmly established in Massachusetts. Scientists are working to come up with effective treatments. According to Ben Staples, arborist at Cicoria Tree Service, there are two treatments that might help but neither has produced certain results. The first is a phosphite soil treatment to stimulate the tree’s natural defenses and keep it generally healthy. The other treatment is a spray for the leaves, but it is still in experimental stages and not yet known if it will effectively target the nematode.
Finally, some arborists recommend pruning your beech trees before late August and September to let light and air circulation dry out the leaves. The nematodes use moisture collected on the leaves to crawl out and swim into the buds for overwintering. The idea is to prevent this step and keep the nematodes trapped in the leaves, which will be shed in the fall.
What should you do if you are concerned about the beech trees on your property? Talk to your arborist about what they recommend. And, until a certain treatment for BLD is found, you should not plant any new beech trees.
The Arbor Day Foundation writes "The American beech is not a tree you plant for fast growth and quick shade—this slow grower is planted for future generations to enjoy. And what a lovely legacy for you to leave."
Let's hope that our beeches survive this latest threat so that future generations can marvel at them as we do today.
