Contenu connexe
Similaire à Elizabeth Dann
Similaire à Elizabeth Dann (19)
Plus de Avocados Australia
Plus de Avocados Australia (20)
Elizabeth Dann
- 2. Queensland Primary Industries and Fisheries
Topics covered
• Experimental results
• Rootstock trials
• Optimisation of phosphonate applications
• Integrated control
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 3. Queensland Primary Industries and Fisheries
Phytophthora root rot (PRR)
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 4. Queensland Primary Industries and Fisheries
PRR linked to seasonal physiology of the tree
- temperature & soil saturation play a major role in PRR severity
• Optimum temperature for
• PRR development 19 – 25° C
• Avocado growth 21 – 33°C
• < 22 °C root growth slows = PRR severe
• > 27 °C avocado grows better than Pc = PRR less severe
• Pc stress on trees greatest in spring
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 5. Queensland Primary Industries and Fisheries
Effect of rootstock on PRR
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 6. Queensland Primary Industries and Fisheries
Velvick clone (7.7) SHSR-04 (2.7)
Reed (8.3)
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 7. Queensland Primary Industries and Fisheries
Clonal Hass (4.8)
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 8. Queensland Primary Industries and Fisheries
Duranbah rootstock trial, tree health
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© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 9. Queensland Primary Industries and Fisheries
This work is continuing…
SHSR-02
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 10. Queensland Primary Industries and Fisheries
Optimising phosphonates
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 11. Queensland Primary Industries and Fisheries
How do phosphonates work?
Dual action:
• High root levels – direct antimicrobial action
• Low root levels – plant defence responses activated
• Moves with photosynthates, accumulates and persists in
plant tissue with greatest metabolic activity at time of
application
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 12. Queensland Primary Industries and Fisheries
Methods of phosphonate application
• Trunk injections
• Foliar sprays
• Bark application
• Soil application
Phosphonate applications must be
continued for the life of the tree
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 13. Queensland Primary Industries and Fisheries
Trunk injection
• Most effective treatment – 20% PO3 injected at even
spacing around the trunk (15mL per metre canopy diam.)
• Central wood retains its transport function (unique in
avocados)
• Injury to xylem near injection site
– Becomes non-conductive
– Replaced by tree in 1 – 2 years
• Healthy trees – 1 annual injection at maturation of
summer flush
• Sick trees – 2 injections - at maturation of both summer
and spring flushes
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 14. Queensland Primary Industries and Fisheries
Foliar Sprays
• Achieve same root concentrations as injections
• Need to monitor root levels to determine number of
applications necessary
• 0.5% (8.3mL/L of the 600 product)
• More sprays required to achieve 0-50ppm, than >50ppm
• No applications within 6 weeks of flowering
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 15. Queensland Primary Industries and Fisheries
Bark Sprays
• Highly effective in young trees where stem has some
photosynthetic (green) activity
• Very effective against trunk cankers
• Unable to achieve and maintain adequate root levels in
older trees, unless applied frequently
• 20% product with 2% bark penetrant
– Higher than 20% causes chemical cincturing
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 16. Queensland Primary Industries and Fisheries
Soil Drenching
• Initial increase in root concentration but quickly declines
• Need to apply monthly to maintain root levels
• Moves in xylem with water transport, thus not effectively
distributed to target tissues
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 18. Queensland Primary Industries and Fisheries
Later maturing varieties eg. Reed
80
phosphorus acid level mg/kg
60
inject
foliar
40 bark
untreated
20
0
ay
l
ov
ug
n
ct
p
ec
Ju
Ju
Se
O
M
N
D
A
Inject, bark, foliar Foliar
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 19. Queensland Primary Industries and Fisheries
Think about using metalaxyl
• Upward movement in transpiration
stream – taken up only by roots
• Prevents colonisation of
roots by zoospores (major)
• Toxic to germinating
chlamydospores (minor)
• If feeder roots healthy, will
be absorbed before
degradation by soil micro-
organisms
• Off patent (cheaper)
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 20. Queensland Primary Industries and Fisheries
Integrated control
• Drainage
• Nursery practices
• Cultural control
• Resistance
• Chemicals
– Phosphonates
– Metalaxyl
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009
- 21. Queensland Primary Industries and Fisheries
Acknowledgements
Thank you to the many growers
and collaborators for supporting
our research!
© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009