A Pennsylvania news release this last summer warns of a new beech pest. At this point, the condition has no name, no cause and no prognosis rather like a doctor saying, “Yup, you’re sick.”
The disease, as we don’t know if any insects, fungus or viral agents are involved, is being called Beech Leaf Disease. It is moving from the west and advancing north and east. Originally discovered in Ohio in 2012, it has spread to at least one western Pennsylvania county, to southwestern New York and it appeared in 2018 on nursery stock in Ontario, although this cannot be confirmed.
The release says, “The disease is affecting the leaves and buds of the trees. The first visible sign is a discolouration of the leaves in which the areas around the veins appear markedly darker than the rest of the leaf. The interior parts of the leaf between the veins then become paler and chlorotic (yellowish), resulting in a distinctive striped appearance. Eventually the leaves shrivel or curl before falling prematurely. It is still not positively known what pathogen is causing this disease, but is thought to be a phytoplasma.” (Phytoplasmas are obligate bacterial parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission.)
As this condition is spreading fast, all tree workers are advised to be on the lookout for it and report it to https://www.eddmaps.org/ontario/ if you are in Ontario, or to your local invasive species centre for other provinces.
Ontario’s Ministry of Natural Resources reported, “No information is available at this time about the spread. A special beech leaf disease survey protocol is currently being developed by researchers in the US and Canada, and will be put in place next year to monitor the extent, severity and rate of spread of BLD.”
Ontario’s MNR reported, “In Ohio, young undergrowth and saplings are reported to die within two years. No definitive mortality data exists for large trees. Initially, their lower branches are affected more than higher branches. Be on the lookout for symptoms of beech leaf disease. Understand that there are many other insect and disease pests of beech that can cause similar symptoms, including mites, aphids, powdery mildew and anthracnose, a general term for a group of diseases that affect plants in similar ways.”
MNR describes the symptoms, “Light and dark banding of beech leaves, especially when looking up into the canopy of the tree. Holding an individual leaf up to the light will also reveal this banding. Puckering and abnormal thickening of leaves can be symptoms of beech leaf disease, however these symptoms can also be caused by other organisms including beech bark disease.”