huanglongbing in china: a historical perspectiveconference.ifas.ufl.edu/citrus15/presentations/5_fri...
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Huanglongbing in China: a Historical
Perspective
South China Agricultural University
Yijing Cen
Department of Entomology
Citrus Huanglongbing Research Laboratory
South China Agricultural University
E-mail: [email protected]
1. History of HLB in China
2. Current distribution and status of HLB in China
3. Control of HLB in China
4. Current research in HLB control
Outline
Fruit production in China
Kiwi
0.5%
Jujube
2.9%
Persimmon
2.4%
Others
9.8%
Longan
1.1%
Banana
7.4%
Grape
6.4%
Lychee
1.6%
Peach
8.6%
Pineapple
0.9%
Citrus
19.6%
Pear
12.3%
Apple
26.5%
Totalyield
105.2MillionTons
（http://citrus948.hzau.edu.cn)
Citrus Varieties in China
Tangerine
37.3%
Mandarine
33.4%
Others
1.3%Pummelo
11.0%
Orange
17.0%
Huanglongbing is the most destructive citrus disease in China
The trees decline and lose their economic value once infected
Taken by Xiaoling Deng
Tree decline due to HLB infection
First report of
HLB in
Chaoshan,
Guangdong
Province, China
(Reiking, 1919)
1. History of HLB in China
A report of HLB in Guangdong in 1923
Journal of Lingnan
Agricultural University
Symptom: Yellow
chicken head
For control, prune it
off
Lingnan Agricultural University:
predecessor of South China
Agricultural University (SCAU)
HLB infected citrus trees in Chaoshan in 1930’S
A dispute persisted over the cause of HLB
between Horticulturists and Plant
Pathologists for over 30 years.
Horticulturists: suggested it was caused by
nutritional deficiencies
Plant Pathologists: suggested it was
caused by pathogen of plant disease
Prof. Lin Kongxiang
(1910-1985)
1 Observations of citrus yellow shoot (huanglong)
disease. Acta Phytopathol. Sinica. 1956a, 2: 1-11.
2 Etiological studies of citrus yellow shoot (huanglong)
disease. Acta Phytopathol. Sinica. 1956b, 2: 13-42.
The dispute persisted until prof. Lin from South China Agricultural University published his 2 papers demonstrating that it was an infectious disease in 1956.
Report of ACP in China:
Taiwan Island in 1908 (Kuwayama, 1908); Macau in 1927 (Husain & Nath, 1927)
First record in mainland China in 1936 (Hoffmann et al. 1936. Journal of Lingnan
Agriculture, 2(1):202-205)
First found on
wampee and
citrus in Lingnan
University
campus
(Guangzhou) in
Nov.1934.
The host plants of Asian citrus psyllid in China
• Murraya
• Citrus
• wampee
Clausena lansium
wampee Murraya exotica
Little attention was paid to ACP until
1953, Prof. Huang Bangkan from
Fujian Agriculture and Forestry College
reported that it was important pest of
citrus young shoots and published
results of his biological studies.
adults
Vector of HLB-Asian citrus psyllid (ACP)
ACP was proved to
be the vector of HLB
in 1976 by:
Guangdong HLB
Research Team and
Guangxi HLB
Research Team
simultaneously.
New vector of HLB found in Yunnan Province,
China: Pomelo psyllid Cacopsylla (Psylla)
citrisuga Yang & Li (Cen et al. 2012)
Adult nymphs Damage phenotype
The history of HLB in Guangdong Overseas Chinese
Citrus Farm reflects the history of HLB in China.
A state-run farm, 2000ha citrus, used to be:
• the most important citrus farm in China
Citrus was first successfully planted up in the mountanious region.
HLB control experience was first developed from this farm
• the biggest citrus farm in Asia
1. History of HLB in China
The history of HLB in Guangdong Overseas Chinese
Citrus Farm
• Before 1976, main citrus pests were big defoliating
insects. Although ACP had not been proven to be the
vector of HLB, it had been very well controlled by
broad-spectrum insecticides while controlling other
pests;
• After 1976, the secondary, small sap-feeding pests,
especially citrus red mites became major pests.
Acaricides use resulted in high populations of ACP
and high infection of HLB. All citrus were removed.
1. History of HLB in China
The history of HLB in Guangdong Overseas Chinese
Citrus Farm
1980-1994 New plantings were assigned as small
plots to workers. However, all agricultural means of
production were provided by the state. ACP and HLB
were under good control, below 0.1% HLB infection
every year.
After 1994 The state stopped investing and all citrus
trees were sold to the workers. Poor ACP control and
nutrition resulted in very high and early HLB
infection in many plots.
1. History of HLB in China
HLB and ACP are now widely distributed in 11 of the 18 citrus plantation
provinces: Guangdong, Guangxi, Fujian, Hainan, Taiwan, Jiangxi, Zhejiang,
Guizhou, Yunnan, Hunan, and south part of Sichuan.
2. Current distribution and status of HLB in
China
Severely infected
Partly infected
Pummelo
Jiaogan
mandarine
Nianju
tangerine
Shatangju
tangerine
Gonggan
mandarine
Mashuiju
tangerine
Hongjiang
orange
Shatangju
tangerine
Chuntianju
tangerine
Wenzhou mandarin,
pummelo
Xinhuigan mandarine Citrus cultivars in Guangdong Province:
Most are mandarine and tangerine,
very susceptible to HLB.
Huazhou
tangerine
ShatangjuTangerine:
The most popular and
famous cultivar in
Guangdong
Very tasty and fertility
ShatangjuTangerine
Infected with HLB
Taken by
Xiaoling Deng
Citrus production in China
（http://citrus948.hzau.edu.cn)
Although greatly impacted by HLB, citrus production has been increasing in
China since 1980s. Up to 2009, total citrus acreage was 2 million ha., total yield
was 25 million tons. Since 2010, about 2.2million ha., 27 million tons per year.
One objective: to develop citrus in areas
where HLB and ACP are absent
.
Mandarin orchard in Hubei Province
Taken by
Xiaoling Deng
Lemon orchards in Yunnan Province
(southwest)
Taken by
Xiaoling Deng
Jiaogan
Chaozhou, Guangdong
High density plantation in HLB present area: about 1000 trees/ha.
In regions where HLB is present, the key
management strategies are:
HLB-free nursery stocks
Sanitation of the planting environment
Improvement of tolerance in uninfected trees
Removal of infected trees when the infection rate
is still low
Insect vector (Asian citrus psyllid) management
3. Control of HLB in China
3.1 Planting HLB-free nursery stocks
Modern, standard disease-free nursery in Hunan
Simple disease-free nursery in Guangxi and Guangdong
1ha per shed
Bad nursery in Guangdong
Bad nursery in Guangdong
HLB infected young citrus trees in Guangdong
Taken by
Xiaoling Deng
Experience from some farmers in Guangdong: planting the 2 or 3
year-old young plants to reduce the risk of HLB infection. Trees are
expected to get fruits 1 year after planted.
3.2 Sanitation of the planting environment
Ganzhou, Jiangxi Province (navel orange)
Taken by
Xiaoling Deng
Infected old grove
In China, successful development
of young plants beside infected
orchards is not possible.
3 years 1 year
2 years
Unfortunately, some farmers do not understand……
Picture from Xiaoling Deng
HLB was not transmitted by the
infected trees to healthy citrus when
they were planted directly together
even after 3 years.
Possibility of the root transmission of HLB
36.67% healthy plants became
infected 1 year after root grafting
with the infected plants.
Xu et al, 2015
3.3 Improvement of the plant tolerance
A healthy Jiaogan (Chaozhou Gan) orchard in Chaozhou, where HLB was
first reported. The owner, Mr. Lai said he only used organic fertilizers,
never used chemical fertilizers. Insecticides were applied only for
dormancy spray.
Applying organic fertilizers is long believed to
improve citrus tolerance to HLB and ACP.
Photo of the owner of the healthy Jiaogan orchard, Mr.
Lai (left) and Mr. Jiacheng Li (right, the Richest
Chinese) .
3.4 Eradication of infected citrus trees
• The only official recommendation in China: eradication of infected trees
• Annual surveys are undertaken during October-December when symptoms are showing up most remarkably.
The only recommended way
in China: eradication of
infected trees
Infected tree stump
lack of agricultural machinery
Treated
method of the
infected
stumps
1 2
3 4
5 Picture from Xianjin Bai
ACP control: Cultural and Chemical control
Cultural control
•Applying of organic fertilizers
•Planting windbreak trees around the orchard
•Control of the new flushes
•Elimination of the infected trees as soon as
they are recognized, because they are more
attractive to ACP.
3.5 Management of the vector-
Asian citrus psyllids
Chemical control
Insecticides are used:
• for dormancy (sanitation) spray after harvest.
• during sprouting. 1-2 sprays for 1 sprouting season.
• before infected trees being eliminated.
Chemical insecticides (such as imidacloprid,
organophosphorus and pyrethroids) are commonly
mixed with 0.5% mineral spray oil to get better
effect and longer term of protection.
ACP adults were
found on the trunk
soon after
insecticides used
Spray result Aerosol sprayer
• Aerosol spray is recommended in Guangxi.
• Cost: 225 Yuan ($36) /ha. Including pesticides and labour.
• More complete control
• Depends on circumstance and weather
Picture from Xianjin Bai
4 Current research in HLB control
1. Antibiotics
Tetracycline was reported to be most effective on HLB in
1970s and has been recommended for elimination of
infection in scions and seeds of rootstock.
2. Heat treatment
3. Nutrition program
Nutritional programs aimed at infected trees have not been
as effective as reported from Florida.
Possible reason: different varieties? soil?
4. Vector control:
Improvement of yellow sticky traps; biological control
In summary
HLB:
1. No solution to the pathogen currently
Candidatus Liberibacter spp.: uncultured, limited in
the phloem of the host plants
2. Can be prevented by the “5 strategies”
Murraya exotica
Future solution aims at the
pathogen: GMO?
Murraya exotica: immune to HLB
Acknowledgement
Elizabeth Baldwin, USDA-ARS Horticultural Research
Laboratory
Philip A. Stansly, James A. Tansey, UF/IFAS/SWFREC
Andrew Beattie, University of Western Sydney
Jianchi Chen, USDA-ARS San Joaquin Valley
Agricultural Sciences Center
Yulu Xia, North Carolina State University
Xiaoling Deng, Changbao Xu, Meirong Xu, and all
students from Citrus Huanglongbing Research
Laboratory, SCAU
Ministry of Agriculture of China
Chinese Scholarship Council
South China Agricultural University
Thank you
for your
attention！
Yijing Cen岑伊静