April 2015 Plant Disease Advisory

eastern filbert blight on tree branch
Fruiting bodies of the Eastern filbert blight pathogen arranged lengthwise along the branch of the highly susceptible C. avellana ‘Contorta’, also known as Harry Lauder’s walking stick.

Eastern filbert blight, caused by the fungus Anisogramma anomala, is an indigenous and relatively harmless pathogen on American hazelnut (also known as filbert, Corylus americana), which is an understory tree in the eastern U.S. However, it is a common and serious disease on European hazelnut (Corylus avellana) grown for nuts or as an ornamental. On susceptible hazelnut, the pathogen causes perennial cankers that expand annually and eventually girdle branches and the trunk, killing the tree. 

eastern filbert blight fruiting bodies close up
Football-shaped fruiting bodies of the Eastern filbert blight pathogen appear about a year after infection, which occurs on tender new growth in the spring.

Management of this disease on susceptible plants requires early detection, repeated fungicide applications, and sanitation. Fruiting bodies of the pathogen are very distinctive: look for rows of large, black, football-shaped fungal fruiting bodies breaking through the bark along the length of the branches. Affected branches should be pruned out well below visible cankers and prunings should be burned or removed from the location. Fungicides containing chlorothalonil or copper hydroxide, applied three or more times in the spring, starting at budswell to budbreak, should control the disease. The fungus infects tender new shoots as they elongate in the spring, but the fruiting bodies do not appear until about a year after infection. 

Early spring or winter is a good time to look carefully for cankers of Eastern filbert blight and prune out affected branches. Early infections often begin on the top of a tree and young cankers may be overlooked because only a few fruiting bodies may be present. Some cultivars of European hazelnut have resistance to the disease; however, breeding programs for hazelnut are located in Oregon and cultivars developed there may not be resistant to strains of the pathogen that are found in the eastern U.S. For more information on this disease refer to the Anisogramma anomala publication at http://wiki.bugwood.org/Anisogramma_anomala_%28eastern_filbert_blight%29.