Sugarcane white leaf disease Lao PDR

Sugarcane white leaf disease
Lao PDR
R.C. Magarey, P. Vongphachanh, P.Songvilay, K. Chittarath, S.
Sayapattha, and L.W.Burgess
BSES Limited, Tully, Queensland
Plant Protection Centre, Vientiane Capital, Lao PDR.
The University of Sydney, Sydney, NSW, Australia

Visit to Lao PDR
Organised by Lester Burgess
• Sponsored by Crawford Fund
• Part of Lester’s extensive involvement in SE
Asia
Visit to investigate sugarcane health
• What diseases?
• What R, D and E needed?
• Assistance to Lao pathologists

Visit to Lao PDR
Activities
• Brief surveys of commercial fields
• Discussions with sugar factory
owners
• Discussions with Lao Government
officials
• Training of pathologists

White leaf disease
• First recognised in Thailand in 1954
• Phytoplasma pathogen
• Transmitted via
• planting material
• Insect vector Matsumuratettix hiroglyphicus (aphid)
• Symptoms
o Leaf chlorosis
o Stunting and poor ratooning
o Trashy stool appearance
o Poor yields

Early symptoms
White leaf disease
– Secondary infection
• Single white or cream streak: young
spindle leaf
– Later: 3 symptom types
• white leaves
• stripe, or
• mottled patterns
– Striping follows vein direction (whole leaf length)

White leaf

Survey location

Survey
Cursory assessment
• Surveys undertaken near
Savannakhet (south-east
area)
• WLD widespread in crops
• Obvious planting of infected
planting material (vegetative)
• Some crops very badly infested
(almost 100% infection)
• Losses likely to be very large

Survey
Reasons for high disease
• Farmers inexperienced in
sugarcane
• New sugarcane mill
• Planting material rapidly
obtained from unreliable sources
• outside Laos?
• Even variety identity uncertain
• Sugar factory staff unaware of
some issues

Survey of Lao PDR
Activities
• Brief surveys of commercial
fields
• Discussions with sugar
factory owners
• Discussions with Lao
Government officials
• Training of pathologists

Action required
Implementation
• Establishment of disease-free
nurseries (HWT)
• Termination of heavily
diseased crops
• Screening for varietal
resistance
• Application of IDM principles

Other issues
Other phytoplasma diseases
• Two other similar diseases in
region
• Grassy shoot (GSD)
• Green grassy shoot (GGSD)
• Similarities
• WLD: chlorosis / stunting
• GSD: stunting / tillering / chlorosis
• GGSD: stunting / tillering

Green grassy shoot (GGSD)

Green grassy shoot (GGSD)

Green grassy shoot (GGSD)

• Add photos
Grassy shoot (GSD)

Grassy shoot (GSD)
Many small
tillers (some
white)

Actions required
Regional work
• Research causal agents
• Clarify differences
• Ensure reliable tests
• Clearly define symptoms
• Research vectors / transmission
• Screen for varietal resistance
• Implement IDM
• Extend information to farmers,
factories, Government agencies

Actions required
Funding
• There is a clear need for funding that
encompasses Laos, Vietnam and
Thailand
Australia biosecurity
• Sugarcane smut illustrated what a
disease incursion can do
• Australian sugarcane industry
seeking to be fore-armed
• Being prepared for the next potential
incursion
• To develop partnerships with
neighbouring countries

Host range
White leaf disease
– Several Poaceae species
including:
• Saccharum spontaneum,
• Cynodon dactylon,
• Brachiaria subquadripara,
• Dactyloctenium aegyptium,
• Chloris barbata and
• Sporobolus fertilis

GGSD vs GSD vs WLD
Symptoms
• GSD
– Some chlorosis of leaves
• GGSD
– No chlorosis on leaves
• WLD
– Variable chlorosis (mottling etc)
– Very few grassy tillers

‘Green grassy shoot disease’ (GGSD)
• First recognised in Thailand in the
early 1990s
• Symptoms
– Profuse tillering
– Narrow and green leaves (no
chlorosis).
– Poor yields
– Poor ratoons

‘Green grassy shoot disease’ (GGSD)
• Early symptoms
– Plant crop: late profuse tillering at
stool base
– No white leaves
– More severe symptoms in ratoons
– Highly susceptible varieties may die

‘Green grassy shoot disease’ (GGSD)
• Cause
– Phytoplasma
• Distribution
– Thailand, Vietnam
– Epidemic developing in Nghe An
Province: serious disease
• GGSD + GSD or GGSD?
• Transmission
– diseased planting material
– insect vector?!

‘Green grassy shoot disease’ (GGSD)
Control
– Disease-free planting material
– Hot water treatment: 50 0 C, 2 hr
– Resistant varieties
• few are resistant
– Cool humid months - incidence
is higher

‘Green grassy shoot disease’ (GGSD)
Host range
Sugarcane is the only known host

• Add photos
Green grassy shoot

Green grassy shoot

White leaves

White leaves
Leaf scald??

‘Grassy shoot disease’ (GSD)
• First recognised: India, 1949
• Symptoms
– Stunting
– Excessive tillering
– Side-shooting: bottom-top of
stalks
– Softening of leaves
– chlorosis (whitening) of leaves
– Proliferation - axillary buds

‘Grassy shoot disease’ (GSD)
Control
– Disease-free planting material
– Hot water treatment (50 0 C, 2.5 hrs)
– Resistant varieties?

‘Grassy shoot disease’ (GSD)
• Cause
– Phytoplasma
• Distribution
– India, Pakistan, Malaysia,
Bangladesh, Sri Lanka, Iran, Sudan,
Thailand, Cambodia, Myanmar

‘Grassy shoot disease’ (GSD)
Host range
– Sorghum,
– Elephant grass (Pennisetum purpureum),
– Brachiaria mutica,
– Cynodon dactylon and
– Imperata arundinacea