Efficacy of Fungicides for Early and Late Blight Control in Tomato

Efficacy of Fungicides for Early and Late Blight Control in Tomato Thomas A. Zitter Jessica L. Drennan Department of Plant Pathology Cornell Universit...
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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)

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