Do you have a beech tree in your yard or favorite park that isn’t looking so hot? The reason behind it may be a new invasive species, a nematode called Litylenchus crenatae subsp. mccannii (Lcm). Nematodes are microscopic, transparent worm-like creatures that live in all kinds of environments like soil, waterbodies, and deserts. But this Lcm nematode lives in leaf buds and leaves of beech trees and causes the deadly beech leaf disease (BLD).
The Deadly Disease
The Lcm nematodes pose no direct harm to humans. They infect the beech leaf buds in summer and fall. The following spring the buds unfurl to reveal leaves with uneven banding patterns, the telltale sign of Lcm nematode damage. It is easy to spot if you hold an affected leaf up to the sky as the damaged bands are opaque in contrast to translucent unaffected leaf tissue (Figure 1). After the infection progresses further, the leaves shrivel and fall off prematurely. The beech tree is left with fewer and fewer leaves which decreases its ability to photosynthesize; this effectively starves the tree of nutrients leading to tree death.
Figure 1: Dark bands show damaged leaf tissue from beech leaf disease. (Photo Credit: Jean Epiphan)
There is no official confirmation as to exactly how the invasive Lcm nematode came to the U.S. nor how exactly it spreads. However, many species of birds eat beech buds, and Lcm nematodes have been found in the mouths or digestive tracts of several bird species. Birds are likely vectors, but they may not be the only ones.
BLD spreads quickly. It was first discovered in Ohio in 2012 and by 2020 has spread to New Jersey. Since then, it has made its way across northern and central Jersey and is spreading southward. Unfortunately, BLD causes rapid tree mortality; a mature tree can die in 6-10 years after infection while young saplings can die in 1-2 years.
To report BLD infection contact the NJFS Forest Health Program at email@example.com or 609-292-2532 (www.nj.gov/dep/newsrel/2022/22_0037.htm).
The Ominous Threats
BLD is deadly to the two main species of beech in New Jersey. The first is non-native European beech (Fagus sylvatica) along with its many cultivars which are commonly planted in ornamental and developed landscapes. The second species is our native American beech (Fagus grandifolia) which is an ecological staple of New Jersey’s climax oak-hickory and northern hardwood forests. Its loss would have devastating impacts to our local ecosystems.
American beech provide abundant resources for wildlife such as larval hosting for hundreds of species of beneficial insects that are essential parts of the forest food web. Beech nuts, a wildlife superfood, are sought-after by forest animals like bears, porcupines, chipmunks, grouse, turkeys, woodpeckers, chickadees, and many more (www.illinoiswildflowers.info/trees/plants/am_beech.htm). Plus, beech provide vital nesting sites and shelter. Without American beech, several wildlife populations will be stressed, decline, or disappear altogether.
As beech leaves fall year after year on the forest floor, they create habitat for overwintering animals and insects, but that is not all. Beech leaves are high in lignan, which slows their decomposition and allows them to accumulate. This process also sustains soil quality and health for forest plants. This thick, tough leaf litter protects soil from erosion, drought, and inhibits invasion; it blocks weeds and invasive plants from germinating and infiltrating beech forests; and it deters invasive worms that destroy forest soil quality, like the jumping worm. Without beech in our forests, soil and ecosystem health is at greater risk.
Mature beech often develop abundant root sprouts that grow into stands of saplings (Figure 2). This dense, clonal growth habit provides many ecological services. The deep shade created helps cool our climate, the many leaves intercept rainwater which reduces stormwater runoff, and the fastidious root systems hold soil in place to prevent erosion, all of which protects our local water quality. These services are especially important where beech live along Category 1 streams and cold-water fisheries as they help conserve their quality (www.state.nj.us/dep/wms/bears/swqs-c1storymap.htm).
Figure 2: A mature beech tree among a dense stand of clonal saplings. (Photo Credit: Jean Epiphan)
The Path Forward
The best way to help, in forests and even your own yard, is to proactively plant (and deer fence) native cohort trees of beech. These are the species of trees that grow alongside beech in our local ecosystems.
The tree species below are the most vital to plant in New Jersey to mitigate beech losses:
- white oak (Quercus alba)
- chestnut oak (Quercus montana)
- swamp white oak (Quercus bicolor)
- shagbark hickory (Carya ovata)
- pignut hickory (Carya glabra)
- mockernut hickory (Carya tomentosa)
- bitternut hickory (Carya cordiformis)
- American holly (Ilex opaca)
- white pine (Pinus strobus)
- black gum (Nyssa sylvatica)
Make sure new tree plantings have the following attributes so they survive, grow faster, and live healthier:
- Local ecotypes sourced from New Jersey (www.jerseyyards.org/jersey-friendly-plants/where-to-buy-native-plants/)
- Smaller-sized stock grown in containers (tubling or 1–3 gallon size)
- Protected from deer damage with physical barriers
- Planted in dense stands of many trees (10–20) to replace one beech
Controlling invasive plants in and around declining beech is also critical as they can rapidly invade in response to added light from canopy loss.
Research pathologists recently discovered some promising treatments that significantly reduce Lcm nematode numbers and disease symptoms. However, they are not suited for most beech forest areas. Nonetheless, treatments can be successful for some small woodlots, ornamental landscapes, and arboreta. Contact your trusted New Jersey Licensed Tree Expert for current treatment options. For more information on hiring a tree care professional follow this link njaes.rutgers.edu/FS019/.
U.S. Forest Service factsheet: Pest Alert – Beech Leaf Disease
Rutgers Plant and Pest Advisory: Beech Leaf Disease in New Jersey
U.S.D.A. – Tellus: What’s Killing Beech Trees?
Bartlett Tree Experts – Research Laboratory Technical Report: Beech Leaf Disease