Soybean Rust Teleconference

1. Soybean Rust Teleconference Disease Cycle & Epidemiology

2. Pathogen Disease Triangle Environment Host

3. Soybean Rust Pathogen Wind Transported 90 years for wind to transport spores of soybean rust pathogen from Eastern Hemisphere to the United States

5. Soybean Rust Pathogen in USA Survival of Rust Fungus Must have living green leaf tissue • Soybean • Common bean (snapbean and etc) • Pea • Kudzu (introduced legume weed in S.E. USA) • Yellow sweetclover (WI) • White clover (WI) • Lupine (WI) • Purple crownvetch (WI) • Ticktrefoil (WI)

6. KudzuPotential Survival of Rust Fungus

8. Assumption • Kudzu will be major winter • survival host • Soybean rust pathogen will not • survive in Wisconsin or Upper • Midwest • - Foliage of perennial hosts will freeze • and die each winter • Soybean rust pathogen must be • reintroduced into Northern States • each growing season

9. Projected Survival of Kudzu

10. Soybean Asian Rust

11. Over-winter in Gulf Coast StatesSouth-North spread of inoculum each growing seasonThe earlier spores arrive, the greater the severity of rust Projected movement of soybean rust pathogen in the USA

12. Soybean Rust Infection Cycle Urediniospores • Spore germination • 80% in 1 hr • 90% in 2 hr Spores germinate Penetration & Infection 10 to 12 hr Pustules 5 to 10 days Urediniospores Spores form within 10 to 21 days Pustule forms spores for 10- 14 days Multi-cyclic Disease

13. (Poppler, 2004)

14. Response of Soybean Rust Pathogen to Environment • Spore Germination • Temp. Range: 46 to 97o F • Temp. Optimum: 60 to 75o F • 8 hrs or more of continuous leaf wetness • >75 to 80% relative humidy or precipitation • Penetration and Infection • Range: 50 to 82o F • Optimum: 65 to 75o F • Minimum of 6 hrs or more of continuous leaf wetness • Hot temperatures, > 86° F may significantly slow development of soybean rust

15. Response of Soybean Rust Pathogen to Environment • Under optimum conditions: • Pustules form in 5-10 days after infection • Spores are produced in 10-21 days • Spores continually produced as long as environmental conditions are conducive • Soybean rust pathogen will go through many cycles of spore production, spore release and new infections in a growing season. • Within optimal conditions, a soybean plant can go from initial symptoms to complete defoliation in 1-2 weeks.

16. Environmental impact on soybean rust • Prolong leaf wetness • 8-12 Hours • Temperatures between 59° F to 86 ° F • Relative humidity between 75-80% required for spore germination and infection

17. Soybean Rust: China & USA 34o N -------------------------------------- 24o N_________________________________

18. Rust epidemic and rain (Sept only), Hubei, China

19. Hubei, China & USA Comparison _________________

20. Environmental impact on soybean rust • Prolong leaf wetness • 8-12 Hours • Temperatures between 59° F to 86 ° F • Relative humidity between 75-80% required for spore germination and infection

21. 1º.05 6.05 13.05 27.05 Epidemiology – r factor Rust: Progress rate [2001/2002)

22. Yield Loss Potential • Potential loss; 0-80% • Rust severity in Gulf Coast area • Crop growth stage at initial infection • July-August weather conditions • Northward movement of inoculum • Weather systems • “green-bridging” • Many unknowns; varieties, planting date

23. Information on Soybean Rust • University of Wisconsin Extension • Soybean Plant Health Website • www.plantpath.wisc.edu/soyhealth • Soybean Plant Health Initiative; North Central Soybean Research Program http://www.ncrsp.com/planthealth • Each website links to many other sites