I decided to repost this from ProMed because I thought it was interesting…who comes up with these disease names!? When I saw it in my inbox of course I had visions of cult activities involving longan fruit in the jungles of Vietnam…yes I have an active imagination.
Witch’s broom gets its name from a deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird’s nest. [Source]
A quick shout out to ProMed which is a great resource for hearing about disease outbreaks of known or unknown etiology around the world…check it out!
But really, Longan fruit is quite prevalent in Thailand as well and it is quite delicious. So, fantastical imagination aside, see below, feel free to read the culti-c disease activities plaguing Longan in Vietnam!
WITCHES’ BROOM, LONGAN – VIET NAM: MEKONG DELTA
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>Date: Mon 15 Aug 2011
Source: Vietnam Today, Vietnam News report [edited]
Witches’ broom disease is blighting longan crops around the Cuu Long
(Mekong) Delta [southern most region of Viet Nam including several
provinces], causing disastrous losses to farmers. In the delta,
around 11 570 ha [hectares] have been blighted by the disease,
figures from local agriculture departments show.
A farmer in Soc Trang Province said longan was the main fruit in his
area, but a witches’ broom epidemic had hit harvests. In Dong Thap
Province famous for longan cultivation, almost the entire 3680 ha of
the crop had been infected, the local Agriculture and Rural
Development Office said. In some communes, most orchards have been
affected reducing longan output by 70 to 90 percent. In Tien Giang,
Vinh Long, and Tra Vinh provinces, the disease has spread rapidly.
Nguyen Minh Chau, Southern Fruit Research Institute, said witches’
broom spread quickly and caused extensive damage. But farmers’
awareness of this disease remained low though his institute had
dispatched officials to educate them about it. Another major concern
was that few farmers had cut down diseased trees and branches, making
it difficult to contain the spread of the disease, he added.
[Longan (_Dimocarpus longan_) is an important fruit crop in parts of
Asia. Witches’ broom (or rosette shoot) is a serious disease of the
crop with reported yield losses of up to 50 percent. It was first
described from China in 1941 where in some areas up to 100 percent of
trees were infected, with higher incidence in mature trees. Since
then it has also been reported from other countries in the region,
for example Thailand and Taiwan.
Symptoms appear on branches and leaves but not on fruit. They may
include distorted mature leaves, unexpanded young leaves, dense
clusters of shoots, poorly developed flowers, as well as abnormal
development of flowers and panicles resulting in “broom-like”
appearance of the inflorescences. Similar symptoms have been reported
from litchi and a close relationship between the 2 diseases is indicated.
The disease is still considered to be of unconfirmed aetiology, but
is suspected to be caused by a filamentous virus transmitted by
vectors such as litchi stink bug (_Tessaratoma papillosa_), longan
psyllid (_Cornegenapsylla sinica_), and a new species of gall mite
(_Eriophes dimocarpi_). The disease is also spread through grafting,
and preliminary evidence suggests that it may be seed transmitted.
Disease management may include orchard sanitation (removal of
potential pathogen reservoirs), phytosanitary measures (disinfecting
cutting tools), and use of clean planting and grafting material.
Resistant crop varieties are available for some areas.
The term “witches’ broom” is descriptive of symptoms only and is
associated with a range of plant diseases caused by different pathogens.
Viet Nam and neighbours:
Viet Nam provinces:
Witches’ broom symptoms on longan flower spikes:
Longan witches’ broom information via:
Research on cause and spread of longan witches’ broom:
Information on longan cultivation and diseases (with pictures):
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