Longan witches broom-associated virus (LWBD or LWBaV) is a species of positive-sense single-stranded RNA virus that has not been assigned to a genus within the family Potyviridae. It is thought to be the cause of witch's broom in longan (Dimocarpus longan), a large tropical tree from southeastern Asia of economic value. Longan witches broom disease is a condition that was first described in 1941. The virus was found in symptomatic plants and absent in healthy plants, but not all of Koch's postulates have been fulfilled.