Over the past several years Beech Leaf Disease (BLD) has become a topic of increasing discussion. BLD affects both Fagus americana and Fagus sylvatica. It was first discovered in Ohio in 2012, although some reports indicate that it was found earlier in Massachusetts. It is associated with the leaf-feeding nematode Litylenchus crenatae mccannii. Studies have been conducted to find a management protocol that is practical in landscapes. Favorable results have occurred that should be implemented to preserve the 10’s of thousands of planted trees in the landscape. However, the practicality of these treatments has very limited use in forests and woodlands where beech make up as much as one-third of our forested land.
Disease Symptoms
Symptoms of BLD include:
Seven other diseases of beech can be misdiagnosed as BLD so one has to be careful not to make the wrong diagnosis. Also, a beech tree can exhibit symptoms of both beech leaf disease and any of these other impacts simultaneously.
Beech bark disease (BBD) symptoms: The symptoms of this disease are concentrated on the bark. A white, fuzzy coating on the tree's trunk and branches is a sign of the scale insect.
Erineum patch symptoms: Yellowish patches appear on the upper side of the leaf. The patches are light green in spring, then fade to orange and eventually brown.
Powdery mildew symptoms: Leaves and stems appear to be covered in a white, powdery substance that resembles powdered sugar. Powdery mildew is caused by native fungi and affects a variety of shrubs and trees. This is a cosmetic disease that does not kill the tree but could cause defoliation if not addressed.
Anthracnose symptoms: Small brown or black spots on leaves that eventually cause dead areas.
Beech blight aphid: These native insects have a fluffy, white outer coating. Also known as "boogie-woogie aphids", the insects will shake or "dance" when the branch is disturbed to ward off potential predators.
Beech leaf rolling aphids: Leaves may curl and appear yellow or faded between the veins. These injuries are caused by aphids feeding on the leaves. This insect is native and feeds on beech without causing much harm.
Plant Pest and Disease Management at Waverly Farm
Over decades of plant production, many serious pest problems have occurred. Often, the nursery industry made a knee-jerk reaction and stopped growing certain genera. Think back to the discovery of boxwood blight. Some advised me to completely stop growing boxwoods. Demand waned for a few years and alternatives were sought. However, I chose to ride it out without the use of fungicides and now demand for boxwood is as strong as ever. Blight is still a problem in landscapes and many nurseries, but we have learned to live with the problem in favor of continued planting of one of America’s most widely used and desired plants.
Now, we are at the beginning stage of boxwood tree moth (BTM). Based on our experience with boxwood blight, we will go through a period of concern and then develop protocols to mitigate the problem. Research currently recommends the placement of traps to inform us of BTM presence so that we can take action for control. Currently, many management systems exist to control BTM. This link is from one of several organizations providing advice:
https://extension.psu.edu/box-tree-moth-management-guide
Although not listed in the link as a control measure, there is discussion for controlling BTM by drenching with a systemic insecticide. At Waverly, we drench our boxwood every other year to control boxwood leaf miner and look forward to determining if such a program will also be effective against BTM. One might argue that every other year drenching may be excessive, but in a nursery environment with 10’s of thousands of boxwood in production in close proximity, it is more difficult to manage leaf miner than it is in a landscape with a few plants. We currently do not have BTM here. However, it was recently discovered in Delaware, and it can travel up to 20 miles per year.
There was a time when the industry was told to stop growing Cornus (Benthamidia) florida because Anthracnose could not be managed. The key, as it turned out, was to simply grow dogwood in sites that provided good airflow. The original huge losses occurred in the understory of wooded areas where high humidity and low airflow dominated the environment. As it stands now, we sell every Cornus (Benthamidia) florida we can grow although it can be a painful process because they grow so slowly.
Recently Lagerstroemia has made the news with bark scale. Again, this iconic tree is widely planted and must be preserved. Control appears to be successful with root drenches using imidacloprid plus other systemic materials. I am not a big fan of growing them here due to winter die-back issues, but with growing zones on the move, we may reconsider.
Managing Beech Leaf Disease
BLD is probably a disease we can learn to live with. At Waverly, we have grown beech since 1992 and have recently started growing finished hedges of Fagus sylvatica. Again, we are seeking a program to ‘manage’ BLD. The following link describes research into a management program that is getting good results:
Although we have not seen BLD here, we are proactively utilizing a fungicide/nematicide spray program described in the article above that has shown great promise. This month (August 2024) we began a trial of four applications spaced three weeks apart to determine if we can avoid the disease. We are using Broadform as described in the research discussed in the above link. I anticipate the cost to be several thousand dollars for chemicals plus labor and equipment to treat 5,000 plants annually. That seems reasonable to preserve a valuable part of our inventory.
Before we and the industry ‘walk away’ from Fagus, we owe it to ourselves to see if a viable management program exists. There are many thousands of beech being grown in our landscapes. It makes sense to see if we can save and continue to plant them.