Dead arm disease is an old term for the death of a part of the grapevine by a wood fungus. In the 1970s it turned out that it was actually a combination of two fungal diseases, caused by the fungi Phomopsis viticola and Eutypa lata. Phomopsis viticola is the fungus that causes Phomopsis dieback, and Eutypa lata causes Eutypa dieback.
Read also: Fungi in the grapevine, that’s rotten!