Southern Rust of Corn: Outline
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Distinguishing common rust vs.
southern rust
Southern rust is potentially much more
destructive
Guidelines to consider in fungicide
decisions
Monitor for stalk strength
Uredia of southern rust (upper
leaf surface view)
Southern rust (right
side) vs. common
rust (left)
Upper leaf surface
Lower leaf surface
Images by Alison Robertson, Iowa State University
Leaf desiccated by southern
rust
“Green islands” of southern
rust
Telia of southern rust
Courtesy Greg Henson,
McLean Co. Extension
“Puccinia pathways” for P.
polysora
?
http://lib.utexas.edu/maps/americas/north_america_ref_2007.pdf
U.S. corn: susceptible to low
levels of resistance
Image at left courtesy Bob Kemereit, Univ. Georgia
Pace of disease progress under
worst-case conditions
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5-6 weeks: From undetected to
substantial damage
2-3 weeks: Can cause substantial
damage, if disease is present…
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…More or less throughout the field (even
at very low levels)
…In all levels of the canopy (lower, middle,
and upper)
Days after mid-silk
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R2 (blister stage): 10-14 days
R3 (milk stage): 18-22 days
R4 (dough stage): 24-28 days
R5 (dent stage): 35-42 days
R6 (physiological maturity): 55-65 days
http://www.agronext.iastate.edu/corn/production/management/growth/yield.html
Watch for loss of stalk
strength