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Truffle Tree Diseases
Celeste Linde
Biosecurity Threats to the Truffle Industry
The most important pathogen/pest biosecurity threats
1. Sudden oak death – Phytophthora ramorum
2. Filbert blight – Anisogramma
3. Xylella fastidiosa – Pierce’s disease
4. Truffle beetle – Leiodes cinnamomea
Plant Health Australia Truffle Biosecurity Plan:Risks
Disease Host Tree Affected plant part
Entry potential
Establishment potential
Spread potential
Economic impact
Overall risk
Sudden Oak Death
Oak and Hazel
Stems, branches, leaves
HIGH HIGH HIGH HIGH-EXTREME
HIGH-EXTREME
Filbert Blight Hazel Branches and stems
MEDIUM MEDIUM HIGH EXTREME HIGH
Xylella(Pierce’s)
Oak and Hazel
Whole plant MEDIUM MEDIUM HIGH HIGH MEDIUM
Sudden oak death: Phytophthora ramorum
Sudden oak death (SOD)
• Host range of +100 species in 40 genera
• Quercus ilex is a known host, Q. robur + hazel are susceptible
• Mortality in oak populations in Western USA –killed > 5 million trees in California and Oregon
• Requires moist conditions for infection
• Survive in harsh environments
Dispersal
• Spread by windblown rain
• Humans (especially nursery
material)
• Soil
• Leaves persisting on trees can be infective for a year
Phytophtora ramorum
• Airborne
• Emerged in 1990s (2001 in USA)
• Three separate evolutionary events
• Four global migration events
Spread and emergence of SOD
Eastern Filbert Blight of Hazels –Anisogramma anomala
• Infects Corylus avelana (hazels)
• Most of the canopy of susceptible trees is usually dead within 7 to 15 years after the first infection (if diseased limbs are not removed).
• Tree health declines slowly at first but then sharply after 3 to 10 years depending on the cultivar.
• Infection occurs in wet weather
End result
Eastern Filbert Blight1. Caused by fungus Anisogramma anomala
2. Life cycle of 2 years
3. Latent period of 12-15 months – BAD NEWS
4. Infection occurs in spring - wet weather
Dispersal
1. Spores forcibly ejected
2. Wind-driven rain and splashing droplets spread spores to young, developing shoots
Control
1. Resistant cultivars is the ONLY option
2. All C. avellana used in Australian truffle industry would be highly susceptible
Threat to Truffle Industry
Initial infection
Sudden Oak Death – after two weeks – wind dispersed
Infection spread to entire region
Filbert Blight – after two weeks of spore production – splash dispersed
Plant Health Australia Truffle Biosecurity Plan:Risks
Disease Host Tree Affected plant part
Entry potential
Establishment potential
Spread potential
Economic impact
Overall risk
Sudden Oak Death
Oak and Hazel
Stems, branches, leaves
HIGH HIGH HIGH HIGH-EXTREME
HIGH-EXTREME
Filbert Blight Hazel Branches and stems
MEDIUM MEDIUM HIGH EXTREME HIGH
Xylella(Pierce’s)
Oak and Hazel
Whole plant MEDIUM MEDIUM HIGH HIGH MEDIUM
Social risks not taken into account in this risk assessment!
Disease survey 2015-2018
• ACT/NSW, TAS, WA
• Quercus robur
• Quercus ilex
• Coryllus avellana
Diseases present in Australia: Hazels• Bacterial blight: Xanthomonas arboricola pv corylina
Diseases and truffle yield
• Some diseases can cause tree death
• Most diseases cause either dieback, stunting or simply poor growth
Questions:
Do these diseases impact on truffle production?
Do these diseases impact on truffle production?• Truffle production not influenced by: Small
stem cankers or tree vigour
– Surprising result for stem cankers – sampling error/only early onset of symptoms?
• Truffle production negatively influenced by: Branch dieback (which may be secondary and usually associated with poor drainage)
Disease factors
• Stem cankers
• Branch cankers
• Branch dieback
• Tree vigour
Stem cankers
Branch cankers
Dieback
Inoculation trial – Hazel: Which fungi are pathogens
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10
20
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Lesi
on
len
gth
(m
m)
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Wilt
Dieback
Stem cankers
Root disease
Branch cankers
Root rot
Lesi
on
len
gth
(m
m)
Inoculation trials planned for Quercusrobur and Quercus ilex
• More fungi to include eg Discula quercine – oak leaf anthracnose
Discula – oak leaf anthracnose
• Defoliation, twig and leaf dieback, leaf distortion and angular necrotic spots on mature leaves.
• Symptoms are usually most severe on the lower branches where moisture tends to remain for longer periods of time.
• Severe outbreaks have been known to kill nearly all the foliage on highly susceptible trees
• Outbreaks usually subside by mid-summer, as the leaves mature and become more resistant to pathogen.
• Succulent growth, however, can still be attacked at any time of the growing season when wet conditions are prevalent.
• Endophyte
• Most prevalent when conditions are moist
• Progresses from leaf infections to twig dieback and branch dieback
• Produce some secondary phytotoxic metabolites that may kill the tree
Phytophthora root rot:Phytophthora cinnamomi
Quercus robur
P. cinnamomi symptoms in roots – Q. robur
Quercusilex
Phytophthora cinnamomi
Control options for Phytophthoradieback
• Improve drainage!
• Chemical trial:• Metalaxyl granule soil application: 50 g/kg, applied at 50 g/m2
• Agriphos 600 stem paint
• Apply when zoospores are active (spring + autumn + rain)
• Monitor: • Tuber root colonisation
• Soil P content
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20
Before
Collwell P (mg/kg)
After one application of Agriphos 600
• Truffle root colonisation ranged from 70-100%.
• Some trees even produced truffles 1 year after inoculation
• Chemical treatment a viable option