Septoria spot of citrus and California
orange exports to South Korea
Brief overview of a successful fruit certification and
export program
J. E. Adaskaveg, Professor
Department of Plant Pathology and Microbiology
University of California, Riverside
Septoria spot of citrus caused by Septoria citri
• A disease of leaves, fruit, and twigs of
oranges, lemons, and grapefruit.
• Occurs in many citrus-growing
countries
Early symptoms:
Small, irregular, pitted,
shallow lesions
Advanced symptoms:
Dark lesions that extend
into the albedo.
Pycnidia
producing
filiform conidia
Economic importance of Septoria spot
• Septoria spot has generally been
considered to be a minor problem
• In 2004, Korean National Plant
Protection and Quarantine Service
(NPQS), detected and rejected
orange fruit that was infected with
Septoria spot from California.
• S. citri is a quarantine pest in
Korea because it has not been
reported on the Unshu orange
grown in the Cheju province.
• Korean market a major export market valued at $112 million was
jeopardized for the CA citrus industry.
The Navel and Valencia Exports to Korea program
(NAVEK)
• Established through negotiations between USDA APHIS
and Korean NPQS to comply with quarantine laws and
help the California orange industry maintain trade with
Korea
• NAVEK is part of a “Work Plan” to certify fruit as diseasefree
• Accomplishment: Korean market maintained through
compliance with quarantine measures following
GAPs and fruit certification of NAVEK - currently
voluntary (mandatory for 6 / 8 years of program).
The Navel and Valencia Exports to Korea program
(NAVEK) - Goals
Compliance with quarantine regulations of Korea
through:
– Development of information on
forecasting and managing the
disease
– Designing rapid detection methods
– Certification of “disease-free”
orange fruit destined for Korea
– Diverting disease-positive fruit to
other markets
– Develop new management strategies
Major accomplishments of NAVEK
• Provided color guides and sampling
strategies based on growers and packers
evaluating and submitting fruit to lab.
• Developed molecular-based detection method
for Septoria spot to be used in a fruit certification
program.
• Implemented on-line submission forms and
confidential reporting system
Numerical Risk Model for forecasting Septoria Spot
Precipitation (mm)
Hrs with
T< -1 C
31-60
61-90
91-120
121-150
151-180
<10
0
1
2
3
4
10-20
1
2
3
4
4
21-30
2
3
4
4
4
>30
3
4
4
4
4
• Developed a disease forecasting system and
optimal timing of fungicide treatments
• Identified and evaluated pre- and postharvest
fungicide treatments for management of the
disease and for inhibition of sporulation
Detection of Septoria spot
Development from a fruit incubation
test based on visual inspections
alone to a molecular-based method
that can detect the pathogen
accurately in the absence of
characteristic signs.
S. citri-specific primers
Orange-specific primers
Development of a Risk Assessment Model for
Forecasting Septoria Spot of Citrus
Numerical Risk Model for forecasting Septoria Spot
Precipitation (mm)
Hrs with
T< -1 C
31-60
61-90
91-120
121-150
151-180
<10
0
1
2
3
4
10-20
1
2
3
4
4
21-30
2
3
4
4
4
>30
3
4
4
4
4
• Model based on accumulation of
low temperature (rind injury)
and precipitation (fungal
growth) is being used for
recommendations of
copper/zinc/lime applications.
• High accumulation of low
temperatures (>69 hr < -1 C) &
low precipitation (0.8-1.8 in) =
High levels of disease
Timing of Second Application (1st application Oct. 15 - Jan. 22)
Oct 15 to
County
Date
Hrs <-1
Range
Pp (mm)
Pp Range
RISK
Fresno
11-Dec
38.3
34-41
19.2
12.6-23.1
1
Tulare
11-Dec
40.5
15-64
25.6
23-28.1
2
Kern
11-Dec
26.0
25-28
19.0
13.7-26
1
Fresno
8-Jan
95.7
85-102
20.44
12.8-23.5
2
Tulare
8-Jan
115.5
62-169
26.4
23.1-28.3
2
Kern
8-Jan
59.7
54-71
19.8
13.8-28
2
Fresno
22-Jan
120.3
103-136
44.8
19.1-35.5
3
Tulare
22-Jan
140.0
81-198
45.9
27.1-30.8
3
Kern
22-Jan
69.7
66-89
21.2
13.8-28
2
Risk Assessment in the 2011-12 Season
Management of the Disease with Fungicides
Fungicide applications are protective treatments.
Copper-zinc and lime treatments have been part of
management guidelines for the disease in California
for the past 65 years.
Development of alternative treatments • The first field-application of the fungicide treatment of
zinc-copper-lime treatment or registered alternative
(Quadris Top) is highly recommended for all oranges
(Navels and Valencias) planned for exportation to Korea.
The treatment should be applied between October
15 and November 30.
Septoria Spot of Citrus –
Evaluate copper and non-copper alternatives
•
Multi-site fungicides:
•
•
•
•
•
Micro-encapsulated coppers (e.g., Kocide 3000, Badge, etc.)
EBDCs (e.g., maneb, mancozeb) – Registration?
DMDCs (e.g., ferbam, ziram) – Un-registerable
Chlorinated hydrocarbons (e.g., chlorothalonil) – In IR-4
registration ongoing
Single-site fungicides
•
•
Azoxystrobin
Other new active ingredients such as difenoconazole alone or
in combination (e.g., QoI and DMI fungicides - Quadris Top).
Quadris Top registered in the US and Korea 2011-12.
Implement new use strategy for CA growers – 2012-13.
Septoria Spot of Citrus – Management
Pre- and postharvest fungicide treatments
Rate
Trt
Field trials on
the evaluation
of preharvest
treatments
Check
Bravo Weather Stick
Inspire
Bravo Weather Stick
Quadris
Kocide 3000
Zinc Oxide
Lime
Bravo Weather Stick
Zinc Oxide
Lime
Quadris Top
Form.
Late Fall
Winter
Spring
(400 gal/A) 11-18-10
2-3-11
Inc. (%)
LSD
--@
@
@
@
@
@
@
@
@
@
@
28.1
0
A
B
1
B
1
B
1
B
1
B
----720SC
6 pints
EC
7 fl oz
720SC
3.2 pints
2F
16 fl oz
30% MCE 1.65 lb MCE
35% MZE
2.5 lb
99%
4 lb
720SC
6 pints
35% MZE
2.5 lb
99%
4 lb
SC
14 fl oz
--@
@
@
@
@
@
@
@
@
@
@
Highly effective treatments for managing Septoria spot:
• New copper formulations
• New fungicides (e.g., Quadris Top) with anti-sporulation
properties.
• Mixtures, rotations
Research Objective:
Efficacy of fungicides in field studies
Single application in early Feb.
Rate
Winter
Spring
Trt
Form.
(400 gal/A)
2-4-11
Inc. (%)
LSD
Check
Bravo Weather Stick
Inspire
Bravo Weather Stick
Quadris
Bravo Weather Stick
Zinc Oxide
Lime
Quadris Top
Thiram
Zinc Oxide
Quadris
Carbamate (Ferbam)
--720SC
EC
720SC
2F
720SC
35% MZE
99%
SC
75WDG
35% MZE
2F
76DF
--6 pints
7 fl oz
3.2 pints
16 fl oz
6 pints
2.5 lb
4 lb
14 fl oz
3 lb
2.5 lb
16 fl oz
15 lb
--@
@
@
@
@
@
@
@
@
@
8.3
2.1
A
B
1
B
1
B
0
2.1
B
B
2.1
1
B
B
@
Treatments were
applied using a dilute
application with a
handgun sprayer set at
400 gal/A.
Single applications of
Quadris Top in midwinter (Jan./early Feb.)
or in fall (Nov.)
were also very effective
in 2009/10 and 2011/12,
respectively.
Plans: Industry guidelines for the management of Septoria spot (CCQC
website) have been revised to include alternative fungicides. Fungicide
labels have been amended and Korean MRLs are in place.
Preharvest
Fruit assays
Postharvest
“Change in quarantine
detection criteria for
Septoria spot to signs
of the fungus”
Experiment 1
Pre/
post
Anti-sporulation
properties of registered
or pending pre- and
postharvest fungicides
Control
Experiment 2
a
abc
a
Enable 8 fl oz
Bravo Weatherstik 192 fl oz
abc
abc
cde
Quadris Top 20 fl oz
c
f
Imazalil 1000 ppm
abc
ab
Penbotec 1000 ppm
bcd
Graduate A+ 16 fl oz
ab
abc
cde
Mentor 8 oz
def
Abound 12.8 fl oz
abc
ef
0
1
bc
2
3
4
0
1
2
3
4
Sporulation rating (0-4)
Laboratory agar and fruit studies identified highly effective antisporulation treatments:
• Pyrimethanil – poor
• Contact multi-site fungicides – intermediate
• New single-site mode of action fungicides propiconazole, QoIs
(Abound, Quadris Top) - highest activity
Septoria Spot of Citrus –
Alternative Treatments for Management
• Preharvest registrations of multi- and single-site materials –
• Standard - Copper-zinc-lime
• Registered alternative – Quadris Top (noting that other export
markets have not established MRLs for a.i.’s in Quadris Top.
• Korean MRLs for Abound (azoxystrobin) and Quadris Top (a
mixture with difenoconazole).
• Full registration for chlorothalonil (Bravo) for all citrus
(oranges, lemons, etc.) ongoing IR-4 residue project since 2009
and MRLs exist for chlorothalonil in Korea and Japan
• Postharvest registrations of single-site materials –
• CODEX MRLs have been obtained in 2009 for azoxystrobin,
fludioxonil, and pyrimethanil.
• Food Additive Tolerance (FAT) for fludioxonil approved in Japan,
whereas pyrimethanil and azoxystrobin are pending.
MRL Guidelines
Current United States, Codex, and current Korean
tolerances of fungicides on orange:
Codex Korea
Crop
Fungicide
US
Orange
Azoxystrobin
10
15
5
Fludioxonil
10
7
5
Imazalil
5
5
Difenoconazole
10
0.6
---
1
Thiabendazole
10
7
10
China has a 0.2 whereas Hong Kong is ND for difenoconazole.
“Develop and modify GAPs and provide information
to growers and packinghouse managers on the
most effective management strategies for Septoria
spot”
• Good Agricultural Practices or GAPs have been developed
from the previous ‘Guidelines’ for the industry in managing
Septoria spot in cooperation with industry, UC, and regulatory
officials. Same practices followed but changes made from
“mandatory” to “voluntary”
 GAPs for Septoria spot management and Color Symptom
Guides for disease identification are posted on the CCQC
website (www.calcitrusquality.org).
 GAPs will be modified to incorporate ongoing research on the
biology and management of Septoria spot of oranges.
NAVEK Certification Program for Septoria
Spot of Citrus – Summary for 2011-2012
Navels total
241/2150 = 11.2%
Tulare Co.
Kern Co.
Fresno Co.
194/1591 = 12.2%
21/300 = 7%
26/241 = 10.8%
Madera Co. 0/18 = 0%
Valencia 25/112 = 22.3%
0
 Total samples
evaluated: 2262
 Zero Detections in
Korea in the last
two seasons!
500 1000 1500 2000 2500 3000 3500 4000
No. samples
In the 2009/10 season, only two detections were found in Korea with
1.3% (56) detections out of 4312 samples evaluated.
Summary
• NAVEK represents an independent certification program
separate from the industry & follows Korean Agreement
• NAVEK is centrally located and has been in operation for
8 years – “Industry is familiar with program”
• No detections in Korea last year • Certification program could be concluded in two more
seasons of zero detections (USDA-APHIS)
• Justified by sufficient awareness of GAPs & ability to
effectively manage disease
• Research has identified, developed, and registered new
fungicides for disease control and to suppress sporulation
• NAVEK funded through orange industry sample
charges
Current Trade Requirements - Key Points of Plant Quarantine
Agreement as of July 2010 Work Plan
 Septoria spot remains a quarantine pest in Korea
 Korean Inspectors will evaluate fruit for fungal sporulation on
import fruit in Korea using standard 2% sampling procedure
 No incubation of fruit by NPQS
 No molecular (PCR) testing by NPQS
 Growers should prevent prevent disease with the application
of preharvest fungicides. Risk assessments based on
environmental conditions and Disease Forecasts will be
made available to the industry.
 Growers should continued to submit samples for molecular
detection that will allow fruit certification from the NAVEK lab
 Guidelines for ‘Good Agricultural Practices’ minimize the
occurrence of Septoria spot
These advances have resulted in a highly efficient & successful program
with minimal burden, while maintaining agreements with Korea
Looking Ahead
Plans are in place for APHIS to specifically re-visit the NAVEK certification
program with Korean NPQS at the end of the 2012-13 season.
The goal is to eliminate the certification of fruit lots based on:
1. No detections of Septoria Spot in Korea for several seasons
(currently 2 and hopefully 3 seasons).
2. New preharvest treatments developed – Quadris Top and Abound
• High efficacy in reducing the disease incidence
• Anti-sporulation properties to prevent dissemination
3. New postharvest treatments – Graduate A+
• High efficacy in reducing the disease incidence
• Anti-sporulation properties to prevent dissemination
4. Demonstrable industry-wide disease management and GAPS
permanently in place.