Beech leaf disease: a disease of unknown aetiology emerging in North America
Since 2012, a new disease of beech trees (Fagus spp.) called 'Beech leaf disease' (BLD) has increasingly been observed in North America. The disease mainly affects F. grandifolia (American beech) but also several other beech species including F. sylvatica (European beech), F. orientalis (Oriental beech). It could possibly affect F. engleriana (Chinese beech) and F. crenata (Korean beech). Early symptoms include dark striped bands between lateral veins of leaves and reduced leaf size. As symptoms progress, aborted buds, reduced leaf production, and premature leaf drop lead to an overall reduction in canopy cover, ultimately resulting in death of sapling-sized trees within 2-5 years. In areas where the disease is established, the proportion of symptomatic trees can reach more than 90%. Beech leaf disease was first observed in the USA, in Ohio (Lake county) in 2012 on F. grandifolia. The disease appears to be spreading rapidly, as it has been subsequently found in other counties in Ohio, in Northwestern Pennsylvania and Southwestern New York; as well as in Canada, along the north shore of Lake Erie in Ontario. In some infested areas (e.g. Ohio and Pennsylvania), citizens are invited to report diseased beech trees, and landowners are urged to avoid moving beech trees or tree parts to prevent disease spread.
So far, the aetiology of Beech leaf disease remains unknown. Research looking at the DNA of diseased trees for bacteria, viruses and phytoplasmas has not been able to identify a possible cause. More recently, attention has been focused on the possible role of nematodes, as a previously undescribed nematode species (Litylenchus sp.) has been observed in association with diseased beech leaves. Research is continuing to try to identify the causal agent(s), to document the impact of Beech leaf disease and develop management strategies.
Sources
INTERNET
Central Pennsylvania Forestry (2018-03-08) Look for Beech Leaf Disease. http://centralpaforest.blogspot.com/2018/03/look-for-beech-leaf-disease.html
Invasive Species. Center for Invasive Species Prevention. Update on Beech Leaf Disease – a threat lacking adequate funding and official action. http://www.nivemnic.us/update-on-beech-leaf-disease-a-threat-lacking-adequate-funding-and-official-action/
Lake Metroparks. Beech leaf disease. A new problem to our forests by J. Pogacnik (2018-08-14). https://www.lakemetroparks.com/along-the-trail/august-2018/beech-leaf-disease
Ohio Department of Natural Resources Forestry Division (2018-08-20) ODNR urges Ohioans to report Beech Leaf Disease. http://forestry.ohiodnr.gov/news/post/odnr-urges-ohioans-to-report-beech-leaf-disease
Pogacnik J, Macy T (2016-07) Forest Health Pest Alert. Beech Leaf Disease. http://forestry.ohiodnr.gov/portals/forestry/pdfs/BLDAlert.pdf
USDA. We need your help. Look for signs of Beech Leaf Disease. http://files.constantcontact.com/3eb6bf61101/a51df273-005c-4330-88eb-e4ea5294ea0d.pdf