Elizabeth Dann

Impacts of fruit disease management
on quality

Liz Dann, Lindy Coates,
Luke Smith, Ken Pegg,
Jan Dean, Tony Cooke

QPIF, Indooroopilly, QLD

Queensland Primary Industries and Fisheries

Topics covered

• Overview of anthracnose and stem-end rot
• Experimental results
• Rootstocks, including nutrition
• Crop load, including nutrition
• Integrated control
• Field fungicides, including strobilurin group

© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009


Postharvest diseases

stem-end rot

anthracnose



Anthracnose (Colletotrichum gloeosporioides)

Infection Symptoms
occurs in field develop
dormant
from fruit set to during fruit
harvest ripening
period



Stem-end rot (many fungi)

• Botryosphaeria spp
• Lasiodiplodia theobromae
• Colletotrichum gloeosporioides
• Phomopsis perseae
• Thyronectria pseudotrichia

Stem-end rot (SER) fungi colonise the
stem tissue of avocado trees without
causing disease

Symptoms develop during fruit ripening


Effect of rootstock on fruit quality & major nutrients



Rootstock affects postharvest disease

• Fruit harvested from T. Whiley’s rootstock trials at
– Childers, QLD (‘Hass’ in 2008 and 2009)
– Walkamin, QLD (‘Shepard’ in 2009)
– Pemberton, WA (‘Hass’ in 2008)
– Hampton, QLD (‘Hass’ in 2007 and 2008)
• Ripened at 23° & 65% RH (Indooroopilly)
C
• Stored 5 weeks at 5.5° then ripened 20° (Maroochy)
C, C
• Assessed for postharvest disease



Effect of rootstock on anthracnose, Hampton 2008

40
% anthracnose a

30 ab

20 bc

c
c c
10

0
3

s
k

d
no
7

-0

as
ic

ee
e

ta
lv

SR
uk

H
R
Zu
Ve

D

SH



Effect of rootstock on fruit skin N:Ca ratio, Hampton 2008

50
Skin N:Ca
40

30

20

10

0
Velvick Reed SHSR- Zutano Duke 7 Hass
03 © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009


Effect of rootstock on leaf N:Ca ratio, Hampton 2009

4
Leaf N:Ca
a
ab ab
3 abc
bcd
cd
d
2

1

0
Velvick SHSR- A10 Reed Duke 7 Zutano Hass
03 © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009


Correlations between disease, yield & nutrient balance –
Hampton 2008

Variable 1 Variable 2 P r (correlation Relationship
coefficient)

Anthracnose Yield per tree 0.044 0.30 -
severity

Anthracnose Fruit skin N:Ca 0.011 0.39 +
severity

Stem-end rot Fruit skin N:Ca 0.013 0.38 +
severity



Effect of rootstock on anthracnose, Pemberton 2008
20 % anthracnose

a

ab

bc

cd
d
d

0
A10 Reed Velvick Duke 7 Zutano Barr
Duke


Effect of rootstock on fruit skin N:Ca ratio, Pemberton 2008

20
N:Ca

a
a
ab
ab
bc

c

0
Velvick A10 Zutano Duke 7 Barr Reed
Duke


Effect of rootstock on anthracnose, Childers 2009
80 % anthracnose a
ab
abc
abcd abcd
60 bcd
cd cd
d d cd

40

20

0
al

3

2
3

al

o
SH 10
S- k

10

e7

k
-0

-0
-0

an
c

S- lvic
ab

ab
A

-A
vi

uk
SR

SR
SR

ut
S-
N
el

-N
C

Ve
-D

-Z
SH
-V

H

C

C

S-
-S

C
C

S-

C



Effect of rootstock on N:Ca ratio, Childers 2009
60
N:Ca

a
40
b
bc bc
bc bc bc bc
bc bc
c

20

0 al
3

2

-D 3
SH al

o
10

10

ck
7
k

-0

-0

-0

an
ic

ab
ab

e
A

-A

vi
SR

SR

SR
lv

uk

ut
S-

N

el
-N

C
Ve

S-

-Z
SH

-V
H
C
S-

-S

C

C
C
S-

S-

C



Significant trends

• Rootstock affects fruit quality
– All locations

• yield ↓ as anthracnose severity ↑
– Childers and Hampton 2008

• anthracnose severity ↑ as N and/or N:Ca ↑
– All locations



Effect of crop load on fruit quality



Effect of crop load on anthracnose disease

100 A
% severity
% incidence B
80
N:Ca
60 a

40 y
b
z
20

0
high load low load high load low load
2007 2008



Effect of crop load on stem-end rot disease

40
% severity
% incidence

20

a
b
0
high load low load high load low load
2007 2008



Crop load affects quality

• ↓ anthracnose & ↓ N:Ca with ↑ crop load

• But, ↑ stem-end rot with ↑ crop load
– Stem-end rot more severe when trees are stressed
– Optimum irrigation and nutrition critical for control



Using fungicides to improve fruit quality



Assessment of new strobilurin products

• Initially a product screening trial (2008)
– pyraclostrobin – Group 11 (previously Group K)
– metiram – zinc based protectant fungicide
– boscalid – locally systemic f’cide with wide activity
– pyraclostrobin + boscalid
– pyraclostrobin + metiram

• Then as part of an anti-resistance program (2009)
– Pyraclostrobin ± metiram



Product screening trial, Duranbah 2008 (cv. Reed)
% severity anthracnose % incidence anthracnose
60 a

50
ab
40
abc
abc
30
bc
20
c
10

0
untreated p'strobin boscalid p'strobin + p'strobin + Amistar
boscalid metiram
p’strobin = pyraclostrobin


Anti-resistance trial, Glasshouse Mtns 2009 (cv. Hass)
% severity anthracnose % incidence anthracnose
120

100
a
80
ab
60 bc
bc bc
c
40 c

20

0
untreated copper Amistar + p'strob 20 p'strobin p'strobin p'strobin
copper + copper 20 + 40 + 40 +
metiram + copper metiram +
copper copper
p’strobin = pyraclostrobin


Most effective and responsible use of fungicides

• Always follow label directions
• Protectants – no “short-cuts” in copper spray program
(every 28 days in fine weather, every 14 days if wet)
• Strobilurins – only Amistar® registered in avocado
– post-infection activity
– use with copper sprays in an anti-resistance strategy
– effective when applied close to harvest and after
extended periods of wet weather
• Postharvest – apply prochloraz within 24h after harvest
– use in conjunction with field spray program
– can’t be used on fruit destined for Europe



Integrated control – the complete picture

Tree Strategic Careful Postharvest
husbandry fungicides harvest care
- nutrition (N, Ca) - protectants and - maturity %DM - cool chain
- canopy mgt post-infection - wet weather - pre-condition
- mulching - phosphorus acid - CA, ethylene
- root health - postharvest
- irrigation © The State of Queensland, Department of Employment, Economic Development and Innovation, 2009


Acknowledgements

Thank you to the many growers
and collaborators for supporting
our research!


Elizabeth Dann

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