management of soybean rust - plant management network
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Fungicides and Their Time of Application for the Control of Soybean Rust
Tristan Mueller
Yield Loss• Potential to cause very large
yield losses • Typically yield loss is greater
the earlier rust is established in field
• Rust spreads very quickly (especially within field)
9/25/2006
10/3/2006
10/10/200611/17/2006
Soybean rust trials in FL
Management of soybean rust
• Resistance– no commercial varieties
available
• Fungicides– Triazole– Strobilurin– Co-packs and
premixes
Single site mode of actionMore systemic than strobilurinsProtectant and curative activity
Single site mode of actionLocally systemic Protectant activity
• Not all available fungicides evaluated in Florida
• Most fungicides were very effective• Some products were better than others
Product Evaluation
Outline
• When is the best time to apply fungicides?
• Soil applied fungicides?
Fungicide Timing
When is the best time to apply fungicides?
Methods
• Locations with rust (6 total)– South America (4)– Southern U.S. (2)
• Fungicides – Headline (strobilurin) – Folicur (triazole)– Headline SBR (co-
pack)– Quilt (premix)
Methods• Timing of application
– Unsprayed control– Growth stage R1, R3, R5– R1 + R3 + R5
• Data collected – Soybean rust severity – Defoliation – Yield – Seed weight
Yield vs. onset of disease
• Fungicides were applied 47 days before to 36 days after rust was first reported– GS R5 epidemic with GS R1 fungicide
application– GS R2 epidemic with GS R5 fungicide
application
• Pirapo and Capitan Meza: rust found at GS R2
• Florida and Georgia: rust found at GS R4
• Bella Vista (both years): rust found at GS R5
Rust observed at GS R2
0
5
10
15
20
25
30
Pirapo Capitan Meza
ControlR1R3R5MaxYi
eld
(bu/
ac)
Rust observed at GS R4
01020304050607080
Florida Georgia
ControlR1R3R5MaxYi
eld
(bu/
ac)
Rust observed at GS R5
05
101520253035404550
Bella Vista (2005) Bella Vista (2006)
ControlR1R3R5MaxYi
eld
(bu/
ac)
Fungicide timing
• Best timing depends on when rust first infects soybeans and severity of infection
• Early infection needs early fungicide application
• Later infection the timing is less critical • Better to spray too early instead of too late
• Fungicides may differ in sensitivity to timing
Conclusions
Florida Quilt Applications
White=non-sprayed control, Yellow=GS R1, Red=GS R3, and Blue=GS R5
YieldCon=42 bu/aR1=45 bu/aR3=46 bu/aR5=50 bu/a
Florida Headline SBR Applications
YieldCon=42 bu/aR1=46 bu/aR3=58 bu/aR5=62 bu/a
White=non-sprayed control, Yellow=GS R1, Red=GS R3, and Blue=GS R5
Fungicide Efficacy
• Quilt still protected yield to some extent, but not as effectively as Headline SBR
• With more severe rust severity fungicide selection becomes more important
Soil applied fungicides
Soil applied fungicides?
Soil applied fungicides-2006
•The higher the rate generally better the control•Some treatments not different than a foliar applied fungicide
Soil applied fungicides-2007
•The higher the rate generally better the control•All treatments better than the non-sprayed control•Some treatments not different than a foliar applied fungicide
• With the fungicide Topguard a soil applied fungicide protected soybean leaves from rust for most of the season
• Many of the treatments were no different than a foliar applied fungicide
Soil applied fungicides
Take Home Message
• Many fungicides work very well – some better than others
• Timing of fungicides are critical for best management of soybean rust
• Soil applied fungicides (Topguard) may be a method to control soybean rust
Acknowledgements• University of Florida
– Dr. Jim Marois– Dr. David Wright– G. Kelly O’Brien– Maynard Douglas
• University of Illinois– Dr. Glen Hartman – Dr. Carl Bradley – Dr. Loren Bode– Dr. Monte Miles
• University of Georgia– Dr. Bob Kemerait
• RARS (Zimbabwe)– Dr. Clive Levy
• CRIA (Paraguay)– Wilfrido Morel
Questions?
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