page_title: Longan witches broom-associated virus
section_title: Symptoms
hierarchical_section_title: Longan witches broom-associated virus / Pathogenesis / Symptoms
caption_attribution_description: Dimocarpus longan (Longan, dragon's eye) Fruit and leaves at Wailuku, Maui, Hawaii. July 21, 2009 #090721-3288 Image Use Policy
context_page_description: Longan witches broom-associated virus 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, 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.
context_section_description: The disease stops young leaves from expanding and distorts mature leaves. Leaves may show vein clearing (yellowed veins), slight blistering, and necrosis. New leaves are smaller, duller, and have rolled margins. Infected leaves are crinkled, narrow, and typically fall off early.  Under a microscope, infected affected bud leaflets may have longer trichomes (hairs), but this may be caused by co-infection with mites and not the virus itself. Infected branches have shoots that grow into dense clusters, which display the eponymous 'witches broom.' The inflorescences do not extend fully, resulting in distorted flowers with crowded panicles. The flowers then produce small, empty fruit if they do so at all. Otherwise the flowers prematurely fall off, leaving a feature looking like a broom. Younger trees typically display more symptoms than mature trees.
  The virus is only found in the sieve tubes, typically associating with the cell membrane and cell walls and rarely in the lumen. Typically the virions will cluster and not be found singly.
  Damage from twig borers such as Hypadima longanae can match the symptoms of LWBD.
caption: Healthy longan foliage
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