postharvest diseases of avocados- from orchard to market...

The New Zealand Institute for Plant & Food Research Limited

Postharvest diseases of avocados-

from orchard to market

A reminder

Dr Kerry Everett

Mt Albert Research Centre

Auckland, New Zealand


Two postharvest diseases

Ø Stem-end rots Ø Body rots


What causes rots?

0

2

4

6

8

10

12

14

16

18

20

C.a. C.g. B.p. B.d. P.

Mea

n n

o.

isola

tions/1

00 f

ruit

Fungus

body rots

stem-end rots

Colletotrichum acutatum

Colletotrichum gloeosporioides

Botryosphaeria parva

Botryosphaeria dothidea

Phomopsis sp.


Are rots a problem?

• USA

• Three strikes and you are out (late ’90’s)

• Rots

• Measles = rots in green fruit

• Australia

• 50% of consumers do not repeat purchase because of poor quality

due to rots (1990’s)*

• Large backlog of NZ fruit in the market place leading to extended

storage and fruit age problems (1997)

• Three issues

• rots

• fruit age

• measles

*Ledger, S., Campbell, T., Banks, A., Atkinson,I, Kernot, I. and Fullelove, G. 1993

Internal quality of avocados in retail shops.

Queensland Department of Primary Industries Internal Report (Avoman). 23pp.


What did we do to fix it?

Research

Avocado Rot Survey

• Three year survey of orchards to identify cultural and grower

practices that affected rots

• Followed it up with replicated trials

Determined:

• the storage limits of fruit

• the criteria for infection

• the relationship between lenticel damage and measles

Logistics

• Reviewed the research that had already been conducted in NZ

• Tightened up timeframes in the logistics pathway

• Cooperation amongst exporters to rationalise flow of avocados

to the market


Avocado Rot Survey

• Sampled 8 orchards in January each year for 3 years

• Sampled an additional 13 orchards for 2 of the 3 years

• Assessed 100 fruit from each orchard for rots

• Collected orchard parameters including spray diaries and weather

• Analysed the data

Everett KR, Boyd LM, Pak HA, Cutting JGM 2007.

Calcium, fungicide sprays and canopy density influence

postharvest rots of avocado. Australasian Plant Pathology

36(1): 22-31.


Fungicide sprays reduce rots

0 2 4 6 8 10 12

0

5

10

15

20

25

30

35

40

45

50R

2=83%

P=0.002

Y = 44.0 - 2.4 X

Mean

no

. o

f fr

uit

wit

h s

tem

-en

d r

ots

(%

)

Mean no. of fungicide applications

0 2 4 6 8 10 12

0

5

10

15

20

25

30

R2=74%

P=0.04

Y = 16.0 + 3.4 X - 0.4 X2

Mean

no

. o

f fr

uit

wit

h b

od

y r

ots

(%

)

Mean no. of fungicide applications


Nutrition affects body rots

0.045 0.050 0.055 0.060 0.065 0.070 0.075 0.080 0.085 0.090 0.095 0.100

0

5

10

15

20

25

30

35

40

45

50

0

5

10

15

20

25

30

35

40

45

50

2000

no.

of

fruit w

ith b

ody r

ots

(%

)

Ca+Mg

K

Y= 396.5 exp(-X/0.02) - 0.51

R2 = 56%

2001


Rainfall inversely related to body rots

0 20 40 60 80 100 120

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

P=0.03

R2=57.4%

Y=0.25-0.002X

Bo

dy

ro

ts (

me

an

se

ve

rity

)

mm rainfall 20 days before picking


Lo

g10 (n

o. o

f fr

uit

wit

h

bo

dy

ro

ts )

C

a+M

g

K

Rai

nfa

ll (

mm

)

Ca+Mg

K

Rainfall (mm) Temperature (°C)

0.050 0.055 0.060 0.065 0.070 0.075 0.080

0.8

1.0

1.2

1.4

1.6

1.8

P=0.02

R2=70.4%

Y=2.5-21.6X

60 80 100 120 140 160 180 200

0.8

1.0

1.2

1.4

1.6

1.8

P=0.03

R2=63.3%

Y=1.78-0.006X

16.2 16.4 16.6 16.8 17.0 17.2 17.4

0.050

0.055

0.060

0.065

0.070

0.075

0.080

P=0.024

R2=67.2%

Y=0.399-0.03X

60 80 100 120 140 160 180 200

0.050

0.055

0.060

0.065

0.070

0.075

0.080

P=0.03

R2=66.2%

Y=0.04+0.0002X

16.2 16.4 16.6 16.8 17.0 17.2 17.4

0.8

1.0

1.2

1.4

1.6

1.8 P=0.01

R2=75.6%

Y=14.1-0.77X

16.2 16.4 16.6 16.8 17.0 17.2 17.4

60

80

100

120

140

160

180

200

Rainfall inversely related to body rots

30 days BH 40 days BH


Canopy index influences body rots dead branches + (canopy density x leaf height inside canopy)/tree spacing

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45 P=0.02

R2=23.3%

Y=0.03+0.12X

mean s

everi

ty (

body r

ots

)

canopy index


3 way analysis of variance (body rots)

Fitted : logten.ca.mg.k. + no..of.months.sprayed + canopy.index

body.r

ots

0.05 0.10 0.15 0.20 0.25 0.30

0.1

0.2

0.3

0.4

R2=67.4%

P=0.000125


Replicated trials

1. Nutrition, canopy management and irrigation

2. Fungicide spray trial

3. Fruit age


Nutrition, canopy management and root

health (root health = irrigation + Phytophthora control)

R + R + R - R - R + R + R - R -

x x x x x x x x

xN+ x xN+ x xN+ x xN+ x

xN- x xN- x xN- x xN- x

x x x x x x x x

x xN- x xN- x xN- x xN-

x xN+ x xN+ x xN+ x xN+

x x x x x x x x

Key

symbol explanation

x Tree

Assessed trees

C-

R Root health

C Canopy management

N Nutrition

Two orchards- organic and conventional

C- = no canopy management

•Dead branches removed from the canopy of all other trees,

•the lower branches were trimmed to a height of 1 m.



Nutrition, canopy management and

irrigation

R + R + R - R - R + R + R - R -

x x x x x x x x

xN+ x xN+ x xN+ x xN+ x

xN- x xN- x xN- x xN- x

x x x x x x x x

x xN- x xN- x xN- x xN-

x xN+ x xN+ x xN+ x xN+

x x x x x x x x

Key

symbol explanation

x Tree

Assessed trees

C-

R Root health

C Canopy management

N Nutrition

Two orchards- organic (5-6 yo) and conventional (15-20 yo)

C- = no canopy management

•Dead branches removed from the canopy of all other trees,

•the lower branches were trimmed to a height of 1 m.

R+ = Root health

• irrigated

• treated with phosphorous acid or mulch (organic orchard)

N+ = Nutrition

•Calcium was applied to the ground under trees.


Results

Factors Body rots Stem-end rots Total rots

Tree n.s. n.s. n.s.

Box n.s. n.s. n.s.

N 0.004 n.s. 0.002

R <0.0001 <0.0001 <0.0001

C n.s. n.s. n.s.

Factors Body rots Stem-end rots Total rots

Tree n.s. n.s. n.s.

Box 0.05 n.s. n.s.

N 0.05 n.s. n.s.

R n.s. n.s. n.s.

C n.s. n.s. 0.03

Conventional orchard (trees 15-20 years old)

Organic orchard (trees 5-6 years old)


Fungicide spray trial

Aims:

• More efficaceous fungicides

• Regional differences?

Procedures

• In vitro screening

• Replicated spray trials


In vitro testing

Fungicide

C. acutatum

C. gloeosporioides

B. parva

B. dothidea

Phomopsis sp.

boscalid <0.1 <0.1 18.2 27.7 74.8

boscalid/

pyraclostrobin

7.0 0.2 2.3 0.2 0.2

KocideÒ 2000DS 0.4 8.1 0.6 15.6 1.5

KocideÒ 3000 7.3 140.9 0.3 4.8 0.1

ChampÔ DP 1.0 57.6 0.1 11.4 2.7

copper

hydroxosulphate

0.1 2.3 4.0 98.2 1.5

dithianon <0.1 <0.1 3.1 18.5 <0.1

fluazinam 0.1 1.9 0.1 0.1 0.1

EC 50 spore germination

Everett KR, Timudo-Torrevilla OE 2007. In vitro fungicide testing for

control of avocado fruit rots. New Zealand Plant Protection 60: 99-103

http://www.nzpps.org/.

Everett KR, Owen SG, Cutting JGM 2005. Testing efficacy of fungicides

against postharvest pathogens of avocado (Persea americana cv. Hass).

NZ Plant Protection 58: 89-95. http://www.nzpps.org/


Fungicide

C. acutatum

C. gloeosporioides

B. parva

B. dothidea

Phomopsis sp.

boscalid 1921.0 >* 837.7 2154.4 >

boscalid/

pyraclostrobin

0.2 0.1 0.2 0.0 0.8

KocideÒ 2000DS 2540.7 647.3 304.7 153.2 105.8

KocideÒ 3000 867.2 297.1 228.1 118.1 101.8

ChampÔ DP 346.7 257.2 1321.7 197.0 193.3

copper hydroxosulphate 910.5 402.1 1645.3 749.9 543.0

dithianon 44.2 201.4 989.6 540.3 17.2

fluazinam 7.8 1.7 6.6 4.3 0.5

*EC50 value is greater than the highest concentration used

In vitro testing

EC 50

mycelial growth

Everett KR, Timudo-Torrevilla OE 2007. In vitro fungicide testing for

control of avocado fruit rots. New Zealand Plant Protection 60: 99-103.

http://www.nzpps.org/

Everett KR, Owen SG, Cutting JGM 2005. Testing efficacy of fungicides

against postharvest pathogens of avocado (Persea americana cv. Hass).

NZ Plant Protection 58: 89-95. http://www.nzpps.org/


Field trials

fluazanim

dithia

non

boscalid

/pyra

clo

str

obin

boscalid

Bio

sta

rt

Cham

p D

P

Kocid

e 3

000

untr

eate

d --

0

10

20

30

40

50

60

70

***

*

Body rots

me

an

seve

rity

(0

-10

0 s

cale

)

Treatment

fluazanim

dithia

non

boscalid

/pyra

clo

str

obin

boscalid

Bio

sta

rt

Cham

p D

P

Kocid

e 3

000

untr

eate

d --

0

2

4

6

8

10

Stem-end rots

me

an

seve

rity

(0

-10

0 s

cale

)

Treatment

Everett, K.R., Timudo-Torrevilla, O.E., Hill, G.N. and Dawson, T.E. 2009.

Field testing alternatives to copper for controlling avocado fruit rots. NZ

Plant Protection 61: 65-69. http://www.nzpps.org/


ANOVA Factors SER BR

Treatment <0.0001 <0.0001

Replicate n.s. n.s.

Region <0.0001 <0.0001

Orchard <0.0001 <0.0001

Fungicide product1 Active ingredient Chemical group

Rate applied Product/100 L

PristineÒ pyraclostrobin/ boscalid

strobilurin/ carboxamide

60 g

KocideÒ Opti copper hydroxide copper 90 g

ShirlanÒ fluazinam pyridinamine 100 mL

4 orchards per region

4 treatments

100 fruit per treatment

8 applications (March to October)

Harvested November


Regional Field Trials

Pyraclostrobin/boscalid Fluazinam Copper hydroxide Untreated

0

10

20

30

40

50

60

c b b a

Ro

t In

cid

en

ce

(%

)

Treatment

SER

BR

a b b b

Everett, K.R., Pushparajah, I.P.S., Taylor, J.T., Astill, M.S., King, D.B.

and Ah Chee, A. 2010. Fungicide spray trial in three avocado growing

regions in New Zealand. NZ Avocado Growers' Association Annual

Research Report Vol. 8: 99-110. available on-line at

www.avocadosource.com


Storage limits of fruit

• Fruit inoculated with Colletotrichum acutatum

• Then placed in coolstore (5.5oC)

• Week 0 fruit was held at 20oC and assessed for SER after 1,3, 4, 6 and 7 days

• After 2 weeks fruit was removed from the coolstore, then every week for 7 weeks

• The fruit was assessed for SER and firmness on 5 occasions as for day 0:

usually 1,3, 4, 6 and 7 days after removal from the coolstore

0 2 3 4 5 6 7 Weeks in coostorage (5.5oC) 5.5oC

20oC

= 20 inoculated fruit &

20 uninoculated fruit


Storage limits of fruit

0 7 14 21 28 35 42 49

0

10

20

30

40

50

60

70

80

90

100

Ripeness of 5 by hand inoculated

control

ste

m e

nd

ro

t in

cid

en

ce

(%

)

time in coolstorage (days)

0 7 14 21 28 35 42 49

0

10

20

30

40

50

60

70

80

90

100

inoculated

control

ste

m e

nd

ro

t i

nc

ide

nc

e (

%)

time in coolstorage (days)

Fruit assessed when ripe

Everett, K.R. & Pak, H.A. 2002

Patterns of stem-end rot development

in coolstorage.

NZ Avocado Growers’ Association

Annual Research Report 2: 68-74

Dixon, J., Pak, H.A., Mandemaker, A.J.,

Smith, D.B., Elmsly, T.A. & Cutting, J.G.M. 2003

Fruit age management: the key to successful long

distance export of New Zealand avocados.



Fruit assessed when hard


Infection criteria

10 12 14 16 18 20 22 24 26 28 30

0

10

20

30

40

50

60

70

80

90

100

C. gloeosporioides 24 hours

Y = 6.75 x (T-20)0.958

x (28.25-T)0.441

T optimum=25.6oC

R2=94.3%

P=0.006

% s

po

re g

erm

ina

tio

n

Temperature (oC)

10 12 14 16 18 20 22 24 26 28 30

0

10

20

30

40

50

60

70

80

90

100

C. acutatum 24hr

Y=3.76 x (T-Tmin

)1.04

x (Tmax

-T)0.73

T optimum=23.3oC

R2=86%

P=0.003

% s

po

re g

erm

ina

tio

n

Temperature (oC)

10 12 14 16 18 20 22 24 26 28 30

0

10

20

30

40

50

60

70

80

90

100

B. parva 24hr

% s

po

re g

erm

ina

tio

n

Temperature (oC)

10 12 14 16 18 20 22 24 26 28 30

0

10

20

30

40

50

60

70

80

90

100

Y = 60

1+e-1(x-17)

R2=46.2%

P=0.06

Phomopsis 24hr

% s

po

re g

erm

ina

tio

n

Temperature (oC)

Everett, K.R. & Pak, H.A. 2002

Infection criteria for pathogens

causing body rots in avocados




Jan

uary

Feb

ruary

Marc

h

Ap

ril

May

Ju

ne

Ju

ly

Au

gu

st

Sep

tem

ber

Octo

ber

No

vem

ber

Decem

ber

Jan

uary

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Phomopsis sp.

C. acutatum

C. gloeosporioides

Kaitaia

Whangarei

TePuke

Tem

pera

ture

(oC

)

10 12 14 16 18 20 22 24 26 28 30

0

10

20

30

40

50

60

70

80

90

100

B. parva 24hr

% s

po

re g

erm

ina

tio

n

Temperature (oC)

Everett & Pak 2002


Annual Research Report 2: 68-74. www.avocadosource.com


Literature review - Postharvest fungicides

Treatment No. of trials % efficacy

Flusilazole 1 68.8

Permanganate (acidified) 1 58

Prochloraz 10 55.3

Benomyl 7 52.7

Hypochlorite 5 36.6

Benzalkonium chloride 1 18.8

Thiabendazole 2 17.8

10% ethanol 2 13

Phosphorous acid 2 4.8

Carbendazim 2 2.5

Kresoxim-methyl 2 8

Boscalid/pyraclostrobin 1 0

Everett, K.R. 2002 Avocado fruit rots: A review of industry funded

research. NZ Avocado Growers’ Association Annual Research Report 2:

8-16. www.avocadosource.com


Literature review - Postharvest fungicides

Prochloraz treatment- apply as soon after harvest as possible

Hours after harvest fruit treated

Not treated 0 2 4 12 24

% rots 73 28 27 35 34 40

y = 3.1x + 23.5 R² = 0.8371

0

10

20

30

40

50

0 2 4 12 24

% r

ots

Hours after harvest fruit treated

Everett, K.R. 2002 Avocado fruit rots: A review of industry funded research.

NZ Avocado Growers’ Association Annual Research Report 2: 8-16 www.avocadosource.com


Finally- to reduce postharvest issues

Apply fungicides

Irrigate the trees and control Phytophthora

Apply calcium

Minimise handling damage

Apply fungicides close to harvest

Get fruit to the marketplace as quickly as possible

Rationalise the flow of fruit to the marketplace so there are no gluts leading

to fruit age problems



Thanks to Ian Hallett, Henry Pak, Shamini Pushparajah,

Olimpia Timudo, Jonathan Rees-George


Treatment No. of trials % efficacy

Methyl jasmonate 1

0

76% ethanol 1 0

Neem oil 1 0

Serenade 1 0

Sporekill 1 0

Antioxidants

(Xedaphen-20 and

BHT + citric acid)

1 0

CO2 shock 1 0

postharvest diseases of avocados- from orchard to market...

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