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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Wilt

Dieback

Stem cankers

Root disease

Branch cankers

Root rot

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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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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