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1/17/2020
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Current status of Stemphylium leaf blight fungicide resistance in onion in New York.Sen. Ext. Assoc. Frank Hay Cornell AgriTech, Geneva
Sen. Ext. Assoc. Christy Hoepting CCE, Albion
Assoc. Prof. Sarah Pethybridge Cornell AgriTech, Geneva
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1/17/2020
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Fungicide Resistance Action Committee.• Fungicides are allocated to a FRAC
group depending upon mode of action.
Two ingredients:
• Fluopyram (FRAC 7)
(SDHI: Succinate dehydrogenase inhibitor - respiration)
• Pyrimethanil (FRAC 9)
• (Anilinopyrimidine fungicides: target methionine biosynthesis)
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History of FRAC group use in NY onion.
Frank Hay/NOFA Winter Conference/2019 4
FRAC group and active ingredient:
Fungicide 2 3 7 9 11Year labelled in NY onion
Rovral® iprodione 2003
Amistar® azoxystrobin 2003
Endura® boscalid 2005
Pristine® boscalid pyraclostrobin 2005
Scala® pyrimethanil 2005
Quadris Top® difenoconazole azoxystrobin 2010
Inspire Super® difenoconazole cyprodinil 2012MerivonXemium® fluxapyroxad pyraclostrobin 2015Luna Tranquility® fluopyram pyrimethanil 2016
FRAC = Fungicide Resistance Action Committee. Fungicides are organized by FRAC code into modes of action.
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Fungicide resistance in NY onion to Stemphyliumleaf blight.
2015 field trial conducted by Christy Hoepting (CCE) showed poorer efficacy of Quadris® (azoxystrobin) vs Quadris Top® (azoxystrobin+ difenoconazole)
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Testing sensitivity of Stemphyliumto azoxystrobin.
Name of Presenter / Event or Location 6
Conidia after 12 hours on agar with:
No fungicide Azoxystrobin 0.5 µg/ml
Calculate EC50 = the lowest concentration of fungicide required to reduce conidial germination by 50%.
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Name of Presenter / Event or Location / Date 7
0.5 µg/ml 50.0 µg/ml
Concentration of azoxystrobin (µg/ml) required to inhibit spore germination by 50% (EC50) for 139 isolates of Stemphyliumvesicarium from 21 NY onion crops in 2016.
8
0
5
10
15
20
25
30
0.02
0.06
0.10
0.14
0.18
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
28.00
30.00
32.00
34.00
36.00
38.00
40.00
42.00
44.00
46.00
48.00
50.00
52.00
54.00
56.00
58.00
60.00
No. isolates in each EC50category
EC50 category (concentration of azoxystrobin required to reduce spore germination by 50%)
48 Stemphylium isolates (34.5%) were sensitive to azoxystrobin.G143A mutation not detected (31 isolates tested)
91 Stemphylium isolates (65.5%) were insensitive to azoxystrobin.G143A mutation detected (74 isolates tested).
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2016 testing: Frequency of isolates of Stemphylium in each EC50 category (concentration of fungicide required to reduce growth by 50%)
4345
43 43
14
2925
31
3 3
96 6
0 0 0 0
13
85
0 0 0 0
10
3
10
0
10
20
30
40
50
No. of isolates in each
EC50category
<0.99
1.0‐10.0
10.0‐49.99
>50.0 µg/ml
Name of Presenter / Event or Location / Date 10
Product FRAC 2 FRAC 3 FRAC 7 FRAC 9 FRAC 11
Quadris® azoxystrobin1
Cabrio®pyraclostrobin1
Endura® boscalid1
Scala® pyrimethanil
Rovral® iprodione
Merivon® fluxapyroxad pyraclostrobin1
Quadris Top® difenoconazole azoxystrobin1
Inspire Super® difenoconazole cyprodinil
Luna Tranquility® fluopyram pyrimethanil
Luna Experience® tebuconazole fluopyram
Tilt® propiconazole
Viathon® tebuconazole (+ FRAC 33)
1 In 2017: Evidence of resistance (laboratory/field) to FRAC 11 (azoxystrobin/ pyraclostrobin) and one FRAC 7 ingredient (boscalid). Endura® was efficacious in C. Hoepting’s field trials in Elba in 2015, but not in 2017.
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Changes in sensitivity of Stemphylium isolates to boscalid (FRAC 7) between 2016 and 2018.
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30.4
19.6
50.0
10.3
28.2
61.5
0.0
20.0
40.0
60.0
80.0
< 1 µg/ml 1‐10 µg/ml >10 µg/ml% of isolates in each EC50category
EC50 (concentration of boscalid required for 50% reduction in growth)
2016 isolates (n = 46) 2018 isolates (n = 78)
2018: Elba (2 crops/18 isolates), Oswego (2 crops/26 isolates), Orange Co. (7 crops/34 isolates)
2018: Sensitivity of Stemphylium to boscalid by region.
Frank Hay/NOFA Winter Conference/2019 12
Isolates from Elba (2 crops), Oswego (2 crops), Orange Co. (7 crops)
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Changes in sensitivity of Stemphylium isolates to pyrimethanil (FRAC 9) between 2016 and 2018.
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54.3
13.0
32.6
17.8
4.0
78.2
0.0
20.0
40.0
60.0
80.0
100.0
< 1 µg/ml 1‐10 µg/ml >10 µg/ml% of isolates in each EC50category
EC50 (concentration of pyrimethanil required for 50% reduction in growth.
2016 isolates (n = 46) 2018 isolates (n = 101)
Changes in sensitivity of Stemphylium isolates to iprodione (FRAC 2) between 2016 and 2018.
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93.5
6.50.0
31.8
47.1
18.0
0.0
20.0
40.0
60.0
80.0
100.0
< 1 µg/ml 1‐10 µg/ml >10 µg/ml% of isolates in each EC50category
EC50 (concentration of iprodione required for 50% reduction in growth)
2016 isolates (n = 46) 2018 isolates (n = 85)
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2018: regional differences in sensitivity to pyrimethaniland iprodione?
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83.3
0.0 0.0
100.0
26.716.7
85.2
17.6
0.0
73.3
0.0
14.8
82.4
0.0 0.00.0
20.0
40.0
60.0
80.0
100.0
Elba (n = 18) Oswego (n =27)
Orange (n = 17) Yates (n = 8) Wayne (n = 15)
Percentage of isolates (%)
Region
Iprodione
<1.0 1.0‐10.0 >10.0 µg/ml iprodione
• Laboratory results suggest a higher proportion of sensitive isolates in Elba? (small number of farms/isolates tested).
• Scala® (pyrimethanil) + Rovral® (iprodione) gave reasonable control of SLB in a field trial in Elba, but not Wayne Co. in C. Hoepting’s 2019 field trials.
• However, with continual use we would expect a similar reduction in efficacy in Elba.
61.1
7.7 5.912.5 13.3
0.0 0.0 0.0
12.5 20.0
38.9
92.3 94.1
75.066.7
0.0
20.0
40.0
60.0
80.0
100.0
Elba (n = 18) Oswego (n =26)
Orange (n = 34) Yates (n = 8) Wayne (n = 15)
Percentage of isolates (%)
Region
Pyrimethanil
<1.0 1.0‐10.0 >10.0 µg/ml pyrimethanil
Changes in sensitivity of Stemphyliumisolates to FRAC 7 active ingredients between 2016 and 2018.
16
93.5
26.7
93.5
31.1 27.7
6.5
36.7
6.5
27.8 24.4
0
36.7
0
41.1 47.8
0
20
40
60
80
100
% of isolates in each EC50category
< 1 µg/ml 1‐10 µg/ml >10 µg/ml
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27.8
50.0
25.021.7
24.022.2
50.0
37.5
30.4
48.050.0
0.0
37.5
47.8
28.0
0.0
20.0
40.0
60.0
Elba (n = 18) Yates (n = 8) Wayne (n = 16) Oswego (n = 23) Orange (n = 25)
% of isolates in each EC50 category
Fluopyram
<1 1‐10 >10 µg/ml
Similar levels of insensitivity to FRAC 7 active ingredients (fluopyram, fluxapyroxad and penthiopyrad) in most regions.
Frank Hay/NOFA Winter Conference/2019 17
Name of Presenter / Event or Location / Date 18
Product FRAC 2 FRAC 3 FRAC 7 FRAC 9 FRAC 11
Quadris® azoxystrobin
Cabrio pyraclostrobin
Endura® boscalid
Scala® pyrimethanil
Rovral® iprodione
Merivon Xemium® fluxapyroxad pyraclostrobin
Quadris Top® difenoconazole azoxystrobin
Inspire Super® difenoconazole cyprodinil
Luna Tranquility® fluopyram pyrimethanil
Luna Experience® tebuconazole fluopyram
Tilt® propiconazole
Viathon® tebuconazole (+ FRAC 33)
= resistance (field + laboratory agree), = developing resistance (laboratory + indications of poorer control in field), = laboratory and field indicate still efficacious.
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Why has fungicide resistance developed?
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• Stemphylium appears to be very adaptable.
• Long history of using FRAC 2, 7, 9 and 11 in NY onion production.
• Growers or neighboring growers do not always adhere to good fungicide resistance management strategies.
• No more than three applications of the same FRAC group within a season.
• No more than two consecutive applications of the same FRAC group.• Rotation between FRAC groups.
• Intensive production system on muck soils (limited crop rotation).
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https://gd.eppo.int/taxon/PLEOAL/photos
Can we reduce the number of fungicides required by forecasting?
Stemphylium vesicarium causes an important disease of pear in Europe (Brown Spot).
A forecasting system has been developed (BSPcast) which predicts risk based on daily leaf wetness duration and mean air temperature during wet periods.
Average of 20‐70% saving in number of fungicide applications.
NIFA CPPM project NYG‐625592 Underpinning the development of an integrated disease management strategy for Stemphylium leaf blight of onion in New York.
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Acknowledgements• Staff:
• Audrey Klein
• Carol Bowden, Sean Murphy, Alex Silva, Elizabeth Burbine, David Strickland, Karen
Luong, Sandeep Sharma
• Nault Laboratory.
• Cornell Co-operative Extension and Geneva FRU staff.
• Growers: for allowing field trials and surveys especially CY Farms, Triple G Farms and
Torrey Farms, Elba.
• Funding:
• Organic Research and Extension Initiative
• Onion Research Development Program.
• NIFA CPPM 2016-70006-25838.
• Federal Capacity Fund 2016-17-149
• NYFVI SCBG SG16-008, SCG18-003
• USDA Hatch Project NYG-625445
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