Invasive Pests
Invasive pests (plants, insects, diseases, and others) cause enormous economic damage, as well as environmental damage. These displace or destroy beneficial and native plants and animals, reduce biodiversity. The annual economic cost is estimated at $1 billion in VA alone, more than $120 billion in the US.
If you think you see the following pest, which is not yet known to occur in Bedford County, please contact the Bedford Master Gardeners at bedfordmg@vt.edu or 540-586-7675. If you are outside of Bedford County, please contact your local Virginia Cooperative Extension Office.
Beech Leaf Disease (BLD) caused by Litylenchus crenatae mccannii, a subspecies of a nematode
Native American beech is susceptible to this disease, as are other beech, such as European, Chinese and Oriental beech. It now is widespread in the northeastern US. BLD was first identified in Ohio in 2012, following serious decline in beech trees. It took several years before the causal agent could be identified as a foliar nematode native to Japan. (Ref 7). The nematode overwinters in buds and detached leaves. Symptoms include leaf and canopy thinning, eventually leading to death of the trees. It was detected in northern VA in 2021 (Ref 1. 2).
The most characteristic symptom of BLD is dark interveinal banding and thickening of leaf tissue as leaves emerge in the spring. Leaf symptoms are unevenly distributed on individual branches and in a tree. As the disease progresses, buds die, branches dieback, the tree declines and eventually dies. The rate of decline is faster for saplings (~3 years) compared to mature trees (~7 years). The banding is apparent when the leaf is backlit. (Ref 2, 3, 4)
The banding that BLD exhibits is quite distinct. It is important to know, however, that some other lookalike issues in the forest affecting beech trees that may result in false identification. Anthracnose, caused by fungi, is relatively common among beech trees and can cause brown spots and dead tissue in leaves. Sometimes, anthracnose also causes leaves to curl. However, the damage anthracnose causes is not restricted to the area between veins. Another disease, erineum patch, also causes patchy leaf damage on beech trees. Unlike BLD and anthracnose, erineum patch is caused by mites that do not threaten the health of the tree. The mites’ damage does not show the distinct banding of BLD. Finally, a native insect known as the beech leaf rolling aphid can also cause curling and fading/yellowing between leaf veins. Beech leaf rolling aphids are also native and do not threaten tree health (Ref 3, 4, 5)
While methods of transmittal are not entirely clear, birds, wind, infested nursery stock, and other means likely are involved (Ref 6). No treatments are currently available for trees affected by BLD; however, several methods are being studied. Common mitigation strategies are likely to be effective at reducing the incidence of BLD and decreasing the likelihood that it is moved to new areas. (Ref 6).
If you see impacted beech trees with the symptoms listed above, please take photos and contact the Virginia Department of Forestry at foresthealth@dof.virginia.gov, or contact the Help Desk for assistance (Ref 7).
References (confirmed 8/9/2023)
- https://spes.vt.edu/affiliated/plant-disease-clinic/plant-disease-alerts.html
- https://spes.vt.edu/content/dam/spes_vt_edu/documents/plant-disease-clinic/disease_updates/BeechLeafDiseaseVirginia-08-2021.pdf
- https://extension.umd.edu/resource/beech-leaf-disease-0
- https://bygl.osu.edu/node/885
- https://bygl.osu.edu/node/1176
- http://www.dontmovefirewood.org/wp-content/uploads/2019/02/Beech-Leaf-Disease-Pest-Alert.pdf
- https://forestupdate.frec.vt.edu/content/dam/forestupdate_frec_vt_edu/newsletter/archives/2021/35_4/Chamberlin.pdf
Submitted by Betsy B., Bedford Extension Master Gardener volunteer and Help Desk Coordinator.