Soybean Rust: What Happened in 2005? What’s Ahead?

1. Soybean Rust: What Happened in 2005?What’s Ahead? Gregory Shaner Purdue University

2. A brief history • Asian soybean rust appeared first in Western Hemisphere in 2001, in Paraguay and southern Brazil • Over the next 2 years it spread to nearly all of Brazil’s soybean production areas • Rust reached the continental U.S. in fall of 2004 • Found in 9 southeastern states, including TN and SE MO • Once there were killing frosts, the fungus was probably eradicated from most of these sites • The fungus was known to overwinter only in central and southern Florida

3. Path of Hurricane Ivan4-16 Sep 2005 • Winds at the periphery of this storm are thought to have carried spores from Colombia, Central America, or the Caribbean to the U.S.

4. Estimated spore deposition: September 19, 2004

5. Soybean Rust in the U.S. Nov 10 - Dec 1, 2004

6. Reasons for concern about soybean rust • Destructive potential • Yields can be reduced up to 80% • Crop over a large area can be affected • Pathogen is airborne • Capable of rapid, long-distance dispersal

7. In anticipation of rust • Knowing it was a matter of when, not if, rust would reach U.S., pathologists began developing strategies for control • Educational programs • Publications • Applications for Section 18 exemptions for fungicides • System for early detection and monitoring rust progress • USDA Web site • Sentinel plots • Diagnostics • Field research

8. Educational programs • Crop Management Workshops • County PARP meetings • ISB-Purdue workshops • DTC spray workshops • DTC summer programs • Regional programs with Dr. Tadashi Yorinori • Special programs (ICIA, Fluid Fertilizer School, Kentuckiana, etc. • First detector training

9. Publications

10. Fungicides labeled for use against soybean rust

11. Section 18 products for soybean rust control

12. Early detection and monitoring • Sentinel plots • Purdue research farms (PACs) • Seed company plots • Farmer-county educator plots • Certified Crop Advisors • Spore trapping • Microscope slides—visual identification • Rain collectors—PCR • USDA web site • P&PDL web site • 800-number phone line

13. USDA-APHIS web site • http://www.sbrusa.net • This site has frequent updates on rust, nationally, and state by state • It’s possible to go back through the season to see how rust developed

14. Commentary for Indiana on USDA soybean rust web site

15. Individual states on USDA soybean rust web site • This shows Alabama, with counties outlined • Red counties are where rust was found as of Nov 23, 2005 • A state commentary appears below the map

16. Purdue Plant & Pest Diagnostic Lab There is a direct link from PPDL home page to soybean rust page

17. Field research • Fungicide evaluation (Shaner and Buechley) • Evaluation of 39 treatments at 2 locations for rust control • Fungicide application technology (Hanna, Conley, Shaner) Effect of: row spacing fungicide timing spray volume on: spray canopy penetration rust control yield

18. Asian soybean rust in 2005 • Not nearly as destructive as we feared • Spread slowly in South • Did not reach Midwest

19. SBR Observation – 02-16-2005 SBR Observation – 03-02-2005 SBR Observation – 03-09-2005 SBR Observation – 03-16-2005 SBR Observation – 03-23-2005 SBR Observation – 03-30-2005 SBR Observation – 04-06-2005 SBR Observation – 04-13-2005 SBR Observation – 02-23-2005 SBR Observation – 04-20-2005 SBR Observation – 05-04-2005 SBR Observation – 05-11-2005 SBR Observation – 05-18-2005 SBR Observation – 05-25-2005 SBR Observation – 06-01-2005 SBR Observation – 06-08-2005 SBR Observation – 06-15-2005 SBR Observation – 04-27-2005 SBR Observation – 06-22-2005 SBR Observation – 06-29-2005 SBR Observation – 07-06-2005 SBR Observation – 07-20-2005 SBR Observation – 07-27-2005 SBR Observation – 08-03-2005 SBR Observation – 08-10-2005 SBR Observation – 08-17-2005 SBR Observation – 08-24-2005 SBR Observation – 08-31-2005 SBR Observation – 07-13-2005 SBR Observation – 09-07-2005 SBR Observation – 09-21-2005 SBR Observation – 09-28-2005 SBR Observation – 10-05-2005 SBR Observation – 10-12-2005 SBR Observation – 10-19-2005 SBR Observation – 10-26-2005 SBR Observation – 11-02-2005 SBR Observation – 09-14-2005 SBR Observation – 11-09-2005 SBR Observation – 11-11-2005

20. What did we learn this year? • Even over the area where rust was found, it was not epidemic • Rust development was initially focal • Little data on comparative fungicide performance • It’s critical to treat before rust has much chance to develop • Little learned about reaction of adapted varieties • Some are being evaluated in a late-planted nursery in the South

21. Purdue fungicide trials • Product comparisons • No rust, so no data on efficacy against that disease • Frogeye leaf spot came in late • Many fungicides suppressed disease, but no effect on yield • Treatments were applied earlier than would have been optimal • Farm-scale trials • Row width (30, 15, or 7.5-in.) had no effect on spray penetration into the canopy • Yields for 7.5- and 15-in. spacing were similar and greater than for 30-in. spacing • Sprayer wheel tracks reduced yield • Repeated passes in the same tracks had no further effect on yield

22. Spray canopy penetration

23. Effect of row spacing on yield • At 7.5-in. and 15-in. row spacing, the wheel track area yielded 5 bu/A less than the non-wheel track area • At 30-in. row spacing, the wheel track area yielded 1.5 bu/A less than the non-wheel track area • Averaged over row spacing, application only at R1 reduced yield 2.1 bu/A in the wheel track area • Averaged over row spacing, applications at R3 or R5 reduced yield by 5 bu/A *The wheel track area was a 15-ft swath that included both sprayer wheel tracks

24. Brazil fungicide trials Values are based on 5 trials conducted in Brazil in 2003/04. Fungicides were applied twice.

25. Changes for 2006 • Sentinel plots • More of them, with an early and normal MG variety at each site • Defer intense scouting until R1 or later • Submit all spotted leaves to lab for microscopic examination • Maintenance of some plots for detailed monitoring of disease progress • Web site and phone line • Fungicide trials • Uniform trial to compare products • Application experiments, including plant health issue • Additional Section 18 exemptions? • Fungicide use recommendations • Wait until rust is close?

26. Differences between Brazil and U.S. Phakopsora pachyrhizi can only survive on living host plant Fungus has a broad host range • There are more green hosts year round in Brazil than in the U.S. • Fungus survives “winter” throughout Brazil • In U.S., fungus will probably only overwinter south of frost zone

27. Rust spreads rapidly in Brazil

28. Rust rapidly defoliates plants

29. Will we have rust in the Midwest in 2006? • No one can say • Partial fallacy of “it takes awhile for the pathogen to become established” • Was weather in 2005 unfavorable? • Cold winter restricted overwintering sites • Early part of summer was dry in much of South • Is there something about the soybean rust fungus? • U.S strain might be less aggressive than Brazilian strains • Spores may be very sensitive to UV light

30. How to prepare for 2006 • It is possible that rust will reach the Midwest in 2006 • Look at USDA web site, PPDL web site, or call the toll-free phone line to find out: • What rust is doing in southern states • What sentinel plots in Indiana reveal • Recommendations for control • There is a possibility that fungicides will be needed to protect the crop