Eutypa dieback, also known as dead arm, is caused by Eutypa lata (synonym: Eutypa armeniacae) which infects fresh pruning wounds when there is adequate moisture on the vine, such as just after a rain.
When there is sufficient water on the vines following rainfall, Eutypa dieback or dead arm disease develops in fresh pruning cuts of grapevines due to infection by Eutypa lata (synonym: Eutypa armeniacae).