Efficacy of Fungicides for
Early and Late Blight Control
in Tomato
Thomas A. Zitter
Jessica L. Drennan
Department of Plant Pathology
Cornell University
Ithaca, NY 14853
Early Blight symptoms
Alternaria tomatophila – light phenotype

Early blight (EB) is an important disease of tomato
Few varieties exist with resistance/tolerance to EB
The Early Blight fungus is now known to exist as two different
species:
• Alternaria solani – traditional Early blight of potato

Infects tomato but much less so
• Alternaria tomatophila – Early blight of tomato with two
phenotypes

Dark Phenotype and Light Phenotype differ in culture but not
morphologically
Light Phenotype is significantly more pathogenic on tomato
Fungicides are required for control for current commercial
varieties
Field Trials (10 years)

Same
• Field: No rotation
• Variety: Supersonic,
Fresh Market, ID
• Spreader rows (EB)
• Weekly fungicide
applications (7-9x)
• Rating: Horsfall-Barratt
Scale (0-11)
• Timeframe the same

Different
• Weather conditions
• Inoculum
Supersonic – EB susceptible
Late Blight
Phytophthora infestans
An oomycete that infects both
potato and tomato
The isolate used, US17, usually
only infects tomato and is less
virulent than other isolates
Isolate US17 inoculated three
times on tomato plot:
August 17, 24, 28
Variety Supersonic – usually foliar
symptoms and/or susceptible to
fruit infection
Forget the Galoshes! Break Out the Hip waders!
New York in 2006 – A very wet summer
The rainiest summer ever recorded in Tompkins Co., NY
May – 2.72”
June – 7.77”
July – 7.54”
August – 5.02”
September – 2.49”
Sections of our field were regularly in standing water
Plants in the mildest depressions in the field suffered from
poor root systems - WET FEET SYNDROME
Supersonic – Late Blight
Susceptible – US-17
Supersonic - Older plant
Another variety – Younger plant
2004 – Br
Quadris Opti
2006 – Br
Quadris Opti
3.2
T216/M201/EB16
T118/M101/EB17/LB0
2004 –
Dithane/Endura/Forum
2006 –
Dithane/Endura/Forum
3.8
T224/M220/EB2
T99/M74/EB10/LB14
Fungicides Tested, 2006
1. Control
2. Bravo Ultrex, 1.8 lb (8x)
3. Dithane Rainshield, 2.0 lb (8x)
4. Bravo Ultrex (5x); Ranman, 2.75 fl oz + Silwet, 2.0 fl oz (3x)
5. Bravo Ultrex (5x); Ranman, 2.10 fl oz + Silwet, 2.0 fl oz (3x)
6. Bravo Ultrex (5x); Ranman, 2.10 fl oz + Silwet, 2.0 fl oz + Dithane, 2.0 lb (3x)
7. Bravo Ultrex (5x); Ranman, 2.75 fl oz + NIS, 0.25 v/v + Dithane, 2.0 lb (3x)
8. Bravo Ultrex (5x); Ranman, 2.75 fl oz (3x) + Dithane, 2.0 lb (3x)
9. Gavel 75DF, 2.0 lb (8x)
10. Dithane, 2.0 lb (8x); Endura, 3.5 oz (3x); Forum, 6.0 oz (3x)
11. Dithane, 2.0 lb (8x); Scala, 7.0 fl oz (3x); Previcur Flex, 1.5 pt (3x)
12. Actigard, 0.33 – 0.75 oz (6 weekly pre-sprays between mid-June to mid-July);
Bravo Ultrex, 1.8 lb (2x), 2.2 lb (2x); Quadris Opti, 1.6 pt (4x)
13. Bravo Ultrex, 1.8 lb (2x), 2.2 lb (2x); Quadris Opti, 1.6 pt (4x)
14. Bravo Ultrex, 1.8 lb (2x); Difenoconazole, 0.34 pt (6x); Mandipropamid, 0.34 pt (3x)
Results
Due to excessive rain and resulting poor root systems, differences in
disease ratings not as pronounced as in previous years
No significant differences among treatments for AUDPC of Early Blight
on tomato foliage, P=0.151
No significant differences among Total and Marketable fruit numbers,
P=0.748 and 0.171, respectively
The AUDPC of Early Blight on Tomato
Foliage vs. Treatment, 2006
180
160
140
120
100
80
60
40
20
1
2
3
4
Dithane
Br/Ranman
9
10
11
12
Dith/Sc/Prev
Act/Br/QO
13
14
0
Control
Bravo
Gavel
Dith/End/Forum
Br/QO
Br/Difen/Mandi
Results
Unmarketable fruit, P = 0.001
The Control and Difenoconazole/Mandipropamid treatment had significantly more
unmarketable fruit than the other treatments
Late Blight on Fruit, P = 0.000
The Control and Difenoconazole/Mandipropamid treatment had significantly more
fruit with Late blight symptoms than the other treatments
Endura/Forum treatment significantly better than Control and Difen/Mandi
treatments but significantly more symptomatic fruit than the other treatments
The Number of Unmarketable
Tomato Fruit vs. Treatment, 2006
60
b
b
50
40
30
a
a
a
a
20
a
a
a
a
10
1
2
Control
Bravo
3
4
9
10
11
12
13
Gavel
Dith/End/Forum
Dith/Sc/Prev
Act/Br/QO
Br/QO
14
0
Dithane
Br/Ranman
Br/Difen/Mandi
The Number of Tomato Fruit Showing Late Blight
Symptoms vs. Treatment, 2006
35
c
c
30
25
20
b
15
10
ab
5
a
1
2
3
a
a
4
9
10
a
a
a
11
12
13
14
0
Control
Bravo
Dithane
Br/Ranman
Gavel
Dith/End/Forum
Dith/Sc/Prev
Act/Br/QO
Br/QO
Br/Difen/Mandi
8/16
8/17
8/18
8/19
8/20
8/21
8/22
8/23
8/24
8/25
8/26
8/27
8/28
8/29
8/30
8/31
9/1
9/2
9/3
9/4
9/5
9/6
9/7
0.00
0.00
0.00
0.00
1.31
0.07
0.00
0.00
0.00
0.16
0.13
0.02
0.59
1.07
0.85
0.02
0.00
0.05
0.65
0.09
0.00
0.00
0.04
E)Spray
5) Bravo 9)Gavel
10)Forum+Dith 11)Previcur+Dith 14)Difen + Mandi
1ST LB
F)2ND LB Ranman Gavel
Endura+Dith
Scala+Dith
Difenoconazole
Forum+Dith
Previcur+Dith
Difen + Mandi
Endura+Dith
Scala+Dith
Difenoconazole
3RD
G)
Bravo
Gavel
LB/Fruit
H)
Br=0;Di=9
Ranman Gavel
0
0
15.0
1.0
34.0
Protectants
chlorothalonil EB +++ LB ++++ YES; Mancozeb EB +++ LB +++ YES
Scala (pyrimethanil) EB +++; LB = no activity
Endura (boscalid) EB +++; LB = no activity (acropetal, translaminar, no vapor
phase; blocks spore germ.)
difenoconazole EB ++++; LB = no activity
Combined activity (EB and LB)
9) Gavel (zoxamide + mancozeb) EB +++; LB ++++ YES
13) Quadris Opti (azoxystrobin + chlorothalonil) EB +++; LB ++++ YES
LB specific
10) Forum (Acrobat) EB = no activity; LB +++
11) Previcur flex EB = no activity; LB ++++
4-8) Ranman (cyazofamid) EB = no activity; LB ++++
14) Revus (mandipropamid) EB = no activity; LB +++ (rainfast + penetrant;
not systemic; use higher rates and shorter interval)
Conclusions –
• In 2006 (unusual conditions), all early blight treatments performed equally
Bravo, Dithane, Gavel, Dithane + Endura, Dithane + Scala, Bravo
4x/Quadris Opti 4x, Bravo 2x/difenoconazole 6x
• During a critical late blight infection period, a LB-effective-product must
be included in each regular spray schedule; options are available
for LB control
• Bravo ++++; mancozeb +++
• Ranman alt. Bravo ++++; Gavel ++++
• Previcur Flex + mancozeb alt. Bravo or mancozeb ++++
• Quadris Opti alt. Bravo ++++
Special considerations
Forum + mancozeb need to alternate with Bravo
mandipropamid must combine with mz or Bravo and alternate with Bravo
(not with difenoconazole)