Management of Soybean Rust Tristan Mueller

Life Cycle Uredinia produce urediniospores Infect host 9-10 days to complete one cycle Uredinia Urediniospores

Yield Loss Potential to cause very large yield losses Soybean rust trials in FL 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 - -talk about draught situation in FL in 2007 where rust came in early, but due to hot and dry weather rust did not develop -rust has the potential for long range spore dispersal, but typically spreads within a field more quickly. 11/17/2006 10/10/2006

Management of soybean rust Resistance no commercial varieties available Fungicides Triazole Strobilurin Co-packs and premixes Single site mode of action More systemic than strobilurins Protectant and curative activity Single site mode of action Locally systemic Protectant activity Resistance- currently being worked on, but will not be available for many years

Outline What fungicides are available and how effective are they? When is the best time to apply fungicides? Can coverage of the soybean canopy be maximized using an air-assist sprayer? Do we need to improve fungicide coverage to better manage soybean rust and improve yield?

Registered fungicides Available Fungicides Registered fungicides Active ingredient Product (trade name) azoxystrobin Quadris azoxystrobin + propiconazole Quilt chlorothalonil Bravo, Echo, Equus myclobutanil Laredo EC, Laredo EW propiconazole Tilt, PropiMax, Bumper propiconazole + trifloxystrobin Stratego pyraclostrobin Headline tetraconazole Domark

Available Fungicides Section 18 fungicides Active ingredient Product (trade name) azoxystrobin + cyproconazole Quadris Xtra cyproconazole Alto flusilazole Punch flutriafol Topguard metconazole Caramba tebuconazole* Folicur, Orius, Uppercut tebuconazole + pyraclostrobin* Headline SBR Section 18 labels expire either in 2009 or 2010, except for tebconazole products. * Section 18 expired so availability will depend on renewal of exemption label – in progress

Fungicides in the Pipeline Active ingredient Product (trade name) famoxadone + flusilazole* Charisma prothioconazole* Not available tebuconazole + trifloxystrobin** Absolute * Decision expected in 2008 ** Decision depends on status of tebuconazole

Product Evaluation Not all available fungicides evaluated in Florida Most fungicides were very effective Some products were better than others I took out which fungicides are better…not sure you want to go there with this crowd. You can maybe point out the better fungicides in the tables on the previous two slides. Take time to explain the aerial shot. I can see differences in defoliation from this picture. When was it taken? Where are the controls, etc….?

When is the best time to apply 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) A trial was put together to determine the best time to apply fungicides. Mention that there also were locations without rust.

Methods Timing of application Unsprayed control Growth stage R1, R3, R5 R1 + R3 + R5 Data collected Soybean rust severity Defoliation Yield Seed weight R1 first flowering R3 pod R5 pod filling

Yield vs. onset of disease Fungicides were applied 47 days before to 36 days after rust was first reported 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 Yield (bu/ac) R1 timing had highest yield (almost as high as three applications) R3 timing still protected some yield R5 timing was not statistically different than the control

Rust observed at GS R4 Yield (bu/ac) R3 (Georgia) or R5 (Florida) timing had the highest yield All timings were better than the control

Rust observed at GS R5 Yield (bu/ac) Late epidemic with low rust severity gave no difference between timings of single applications of fungicides Why was there a yield increase? Other diseases observed? Or from rust?

Fungicide timing Conclusions 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

Florida Quilt Applications This is an aerial view of the 2006 Quincy, FL location take on 11/17/2007. This location soybean rust was found at GS R4. Can see differences between fungicides and fungicide timings I will take you through the plots of 2 fungicides (the best and the worst) at different timings For Quilt none of the timings protected from defoliation Yellow=GS R1, Red=GS R3, Blue=GS R5, and White=non-sprayed control

Florida Headline SBR Applications R3 and R5 better than R1 Yellow=GS R1, Red=GS R3, Blue=GS R5, and White=non-sprayed control

Can fungicide coverage be maximized using an air-assist sprayer?

Methods Urbana, IL 2005 and 2006 Air-assist sprayer (JACTO)

Methods Air-assist blows air over the nozzle which helps propel drops into the canopy Compared five nozzle types with and without air-assist Hollow cone Air Induction Ultra-Lo Drift Turbo TeeJet

Spray card setup 18 Kromekote cards per plot Placed at  and  canopy Scan cards to determine percent coverage

2005 Air-assist results Air-assist Without Air-assist

2006 Air-assist results Air-assist Without Air-assist

Air-Assist Sprayer Summary Less dense canopy No advantage Nozzles producing medium-sized drops resulted in the best percent coverage All nozzles had about the same coverage in the lower canopy Denser canopy Better coverage, especially with smaller droplets JA hollow cone nozzle with air-assist had the best coverage in the upper and lower canopy

Fungicide Coverage Do we need to improve fungicide coverage to better manage soybean rust and improve yield?

Methods Florida and Georgia, 2006 Pressures: 30, 50, and 70 psi Spray volumes: 10 and 20 gpa Nozzle types: Turbo TeeJet and Ultra Lo-Drift

Methods Fungicide: Folicur (tebuconazole) Data collected Coverage in soybean canopy Disease severity Yield

Results – Coverage (spray volume) Upper canopy Lower canopy 20 GPA treatments averaged twice the coverage of 10 GPA but resulted in equal amounts of fungicide that reached the cards

Results – Coverage (pressure) Upper canopy Lower canopy In the upper canopy 70 psi typically had better coverage than 50 and 30 psi In the lower canopy no differences in coverage among pressures

Results – Coverage (nozzle) Upper canopy Lower canopy Turbo TeeJet nozzle has medium droplet spectrum and Ultra Lo-Drift has large droplet spectrum. Turbo TeeJet had a slight increase in coverage in the upper canopy In the lower canopy no differences in coverage between nozzles

Results – Soybean Rust No difference among treatments sprayed with fungicides for rust severity Non-sprayed control had higher rust severity than all of the treatments sprayed with fungicide

Results – Yield No difference among treatments sprayed with fungicides for yield For both locations, the non-sprayed control had the lowest yield

Fungicide Coverage Summary 20 gpa had twice the coverage 10 and 20 gpa results in equal amounts of fungicide on leaves In general, 70 psi resulted in better coverage No difference in disease severity or yield

Second Coverage Study Florida, 2007 Compare normal fungicide coverage with complete fungicide coverage Normal = 15 gpa at 35 psi Complete = 70 gpa with back pack sprayer (all leaves 100% covered)

Second Coverage Study Still no differences

Take Home Message Many fungicides work very well – some better than others Timing of fungicides are critical for best management of soybean rust Differences in coverage did not affect efficacy of fungicides

Acknowledgements University of Illinois University of Florida Dr. Glen Hartman Dr. Carl Bradley Dr. Loren Bode University of Florida Dr. Jim Marois Dr. David Wright G. Kelly O’Brien Maynard Douglas University of Georgia Dr. Bob Kemerait RARS (Zimbabwe) Dr. Clive Levy CRIA (Paraguay) Wilfrido Morel USDA Dr. David Walker