Understanding myrtle rust epidemiology and host specificity to determine disease impact in Australia Geoff Pegg Senior Forest Pathologist, DAFF Queensland biosecurity built on science Cooperative Research Centre for National Plant Biosecurity
Background Myrtle rust = Puccinia psidii First detected in NSW in April 2010
- Central coast - Extends from Tweed Heads to Batemans Bay area
Identified in nurseries in Queensland in December 2010
- Initially limited to the south-east region - January 2012 – as far north as Rockhampton - May 2012 – far Nth Qld
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Project aims Determine host range and impact on native Myrtaceae Identify factors influencing spread and severity of myrtle rust Investigate variability and host specificity of Puccinia psidii
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Impact Agonis flexuosa
Melaleuca polandii
Anetholea anisata
Melaleuca quinquenervia
Austromyrtus dulcis
Melaleuca viridiflora
Backhousia citriodora
Rhodamnia angustifolia
Chamelaucium uncinatum
Rhodamnia costata
Choricarpia leptopetala
Rhodamnia dumicola
Decaspermum humile
Rhodamnia maideniana
Eugenia reinwardtiana
Rhodamnia rubescens
Gossia acmenoides
Rhodamnia sessiliflora
Gossia gonoclada
Rhodomyrtus psidioides
Gossia hillii
Rhodomyrtus tomentosa
Gossia inophloia
Syzygium jambos
Lenwebbia prominens
Syzygium oleosum
Melaleuca fluviatilis
Tristania neriifolia
Melaleuca leucadendra
Xanthostemon oppositifolius
Melaleuca nodosa
 More than 120 species from 35 genera - 31 species considered as highly or extremely susceptible biosecurity built on science
Rhodamnia angustifolia
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Monitoring the impact in native forests Rhodamnia rubescens (scrub turpentine) Key understory species Highly susceptible to myrtle rust Fauna use flowers and fruit biosecurity built on science
Plot of the mean values (solid lines) for mean number of new shoots, mean number of leaves, mean incidence and mean severity against the measurement time. Red is for the control trees and Blue for the treated trees. The dotted lines are the 95% confidence interval around the mean values. biosecurity built on science
Unsprayed
Sprayed
Significant increase in foliage production on biosecurity built on science fungicide-sprayed trees after 6 months
Impact on flowering
Melaleuca leucadendra
Photos G. Pegg
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Flower & fruit infection
100
100
90
90
80
80
70
70
Fruit infected (%)
Flowers infected (%)
 Rate and level of flower & fruit infection
60 50 40 30
60 50 40 30
20
20
10
10
0
0 1
3
6
8
10
Time (days)
15
18
21
26
1
4
15
24
Time (days)
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Melaleuca quinquenervia Impact of rust on regeneration - Monthly assessments Disease incidence and severity Impact on; - Growth - Survival - Flower/seed production
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100
Average disease incidence on new shoots
80 60 40 20 0 Aug
Sept
Oct
Nov
Dec
Feb
Mar
Apr
May
Month
No foliage flush present
5
Disease rating
Disease incidence (%)
Melaleuca quinquenervia
4 3 2 1 0 Aug
Sept
Oct
Nov
Dec
Feb
Mar
Apr
May
Average disease severity rating on new shoots
Month
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Factors influencing spread and severity of rust Patterns of disease development - Regional – tree level
Rate of spread within planting Influence of climate - Temperature - RH - Dew point/leaf wetness
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South east Queensland 300 Myrtle rust reports 250
Species reported
200
150
100
50
Au gu st Se pt em be r O ct ob er N ov em be r D ec em be r Ja nu ar y Fe br ua ry M ar ch
Ju ly
Ju ne
M ay
Ap ri l
ec em be r Ja nu ar y Fe br ua ry M ar ch
0
D
Myrtle rust reports
Syzygium jambos reports
Month
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South east Queensland
300 Myrtle rust reports 250
Species reported
200
150
The Australian – 10th April 2011
Channel 9 Brisbane 6pm news – mid May 2011
100
50
Au gu st Se pt em be r O ct ob er N ov em be r D ec em be r Ja nu ar y Fe br ua ry M ar ch
Ju ly
Ju ne
M ay
Ap ri l
ec em be r Ja nu ar y Fe br ua ry M ar ch
0
D
Myrtle rust reports
Syzygium jambos reports
Better Homes & Gardens 24th Feb 2012
Month
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Rate of infection Rhodamnia sessiliflora
Shoots infected (%)
100
Average days until infection
90
Average pustules per shoot
80
Time of infection Level of infection
70 60 50 40
- Climate data captured
30 20
Temp RH Dew point Leaf wetness
10 0 Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Month
30 new shoots – no infection
No new shoots – large number of flowers produced
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Spore trapping 160
Spore count 140
Temperature oC RH (%)
Spore count/climate data
120
Dew point reached (%)
100 80 60 40 20 0 0000-0245 0300-0545 0600-0845 0900-1145 1200-1445 1500-1745 1800-2045 2100-2345 Tim e of day
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Variability & host specificity Baseline data for detecting a change in pathogen population - Selection of isolates for use in breeding programs - Information on strain present in relation to strains not present in Australia to protect trade
Collection of isolates & optimising screening protocols - Baseline date on pathogen population 60 isolates - Selection of a differential set Monitoring change biosecurity built on science
Screening protocols Characterise susceptibility of key Queensland eucalypt species to Puccinia psidii Corymbia - Spotted gum & Corymbia hybrids Species, Provenance, Family Eucalyptus species - Eucalyptus argophloia – Chinchilla white gum - Eucalyptus cloeziana – Gympie messmate
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4
Eucalyptus and Corymbia spp
3.5
Disease rating
3 2.5 2 1.5 1 0.5 0 E. argophloia
C. citriodora
C. variegata
C. henryi
Host species
C. torelliana
E. cloeziana
Based on Brazilian rating system 1= "Immune“ – yellow flecks 2 = HR – no evidence of pustules; necrotic lesions 3 = S1 < 0.8mm in diameter 4 = S2 pustules of 0.8-1.6mm diameter 5 = S3 >1.6mm in diameter biosecurity built on science
6
5
ď&#x201A;§ C. variegata
Disease rating
4
- Woondum families
3
2
1
0
11185-18
11185-19
11185-16
11185-13
11185-10
11185-20
11185-14
11185-17
11185-15
11185-11
11185-12
Seedlot
ď&#x201A;§ Individual seedlings within seedlots 6 6
5 5
4
Disease rating
Disease rating
4
3
3
2 2
1
1
0
0
1
2
3
4
5
6
7
8 Seedling
9
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Seedling
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Conclusion Large host range with impact on environmentally and commercially important species - Growth - Flower/fruit production Regeneration
- Impact yet to be fully understood
Triggers for disease spread & severity yet to be determined - Host/pathogen interaction - Climate – tropical/subtropical/temperate
Baseline pathogen population established - Screening method - Need to conduct pathogenicity tests - Selection of differential set
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Thank you CRC Plant biosecurity Dr Suzy Perry, Dr Angus Carnegie, Dr Kylie Ireland, Dr Fiona Giblin, Peter Entwistle, Dr David Lee, Jeremy Brawner DAFF Queensland - Biosecurity Queensland, Agri-science Queensland For more information, please email Geoff.Pegg@daff.qld.gov.au; myrtlerustprogram@deedi.qld.gov.au
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