Southern Rust in Corn
Biology and Management
Southern rust of corn is caused by the fungus Puccinia polysora. Southern rust
can by identified by orange-to-brown masses of spores that break out through
the upper leaf surface. Leaves, stalks, and ear husks may be infected. Southern
rust typically produces spores densely on the upper leaf surface and only sparsely
on the lower leaf surface. Pustules of southern rust may also have a yellow halo.
In contrast, common rust (caused by Puccinia sorghi) produces spores on both
surfaces, often in streaks.
The pathogen that causes southern rust does not overwinter in the Corn Belt.
Consequently, these fungal spores must be blown in each year, and disease
occurrence is dependent upon wind dispersal from the south in early- to midsummer. Therefore, southern rust incidence varies from year to year.
For disease to occur, the following four
interactive factors must be present:
n
A susceptible plant to serve as the host
n
A pathogen that is compatible with the host
n
An environment that favors the growth
Environment
Time
and reproduction of the pathogen
n
Time for disease development
Disease will not develop if any element of
the disease pyramid is missing.
Pathogen
Technical Information Bulletin
Host plant
Optimal Conditions for
Southern and Common Rust
Temperature
Humidity
Southern
Rust
75° to 82°F
High
Common
Rust
61° to 77°F
Wet Conditions
Best Use Recommendations for Headline AMP® Fungicide and Priaxor® Fungicide
For control of late season southern rust infections, apply Headline AMP fungicide at VT to R3. Two applications
may be required in areas of heavy disease pressure. Example: Apply Priaxor fungicide pre-tassel followed by
Headline AMP fungicide at VT to R3 or apply Headline AMP fungicide at VT/R1 followed by Headline AMP
fungicide 7 to 14 days later.
Use Rate (Headline AMP Fungicide): 10 – 14.4 fl oz/A; (Priaxor Fungicide): 4 – 8 fl oz/A
Labeled Crops: Corn (all types)
Application Information
n Aerial: 2 GPA minimum; Ground: 10 GPA minimum
n PHI (Headline AMP Fungicide): 20 days for field and popcorn grain, 7 days for seed and sweet corn;
(Priaxor Fungicide): 7 days for sweet corn, 21 days for all other types
n REI: 12 hours
Adjuvants
n
Adjuvant flexible; however, see label for adjuvant restrictions after the V8 stage and prior to the VT stage of corn growth
Southern Rust Control with Headline AMP Fungicide
Southern Rust Research Trial Evaluating
Sequential Fungicide Applications (VT fb R2)
Untreated
Rust in
Untreated Area
76
Stratego® YLD x 2
48
Preemptor™ x 2
Headline AMP
Fungicide
10 fl oz/A
Aproach® fb Aproach Prima 31
Headline AMP Fungicide x 2 25
BASF sponsored on-farm demonstration, Blackwell, OK, 2014. Photo taken August 6 (40 DAT)
Priaxor Fungicide fb Headline AMP Fungicide
Raising the Bar on Southern Rust Disease Control
54
0
10
20
30
40
50
60
70
Percent Disease Severity (20 days after 2nd application)
80
Sequential Fungicide Applications (VT fb R2)
Untreated
Untreated
134
164
Stratego YLD x 2
174
Preemptor x 2
Priaxor Fungicide
fb Headline AMP
Fungicide
BASF sponsored University research trial, Attapulgus, GA, 2014. Sequential Applications
(V7 followed by R1). Priaxor fungicide was applied at 4 fl oz/A, Headline AMP fungicide was
applied at 10 fl oz/A.
167
Aproach fb Aproach Prima
Headline AMP Fungicide x 2
120
130
140
150
Yield (bu/A)
180
160
170
180
BASF sponsored University research trial, Brewton, AL. Fungicide applications @ VT followed
by R2. Preemptor (tested as Fortix®) @ 5 fl oz/A, Aproach @ 9 fl oz/A, Aproach Prima @ 6.8 fl
oz/A, Stratego YLD @ 4 fl oz/A, Headline AMP fungicide @ 10 fl oz/A.
To learn more about crop protection products
from BASF, visit www.agproducts.basf.us
Always read and follow label directions.
Grow Smart is a trademark and Headline AMP, and Priaxor are registered trademarks of BASF Corporation.
Stratego is a registered trademark of Bayer CropScience. Aproach is a registered trademark of DuPont.
Fortix is a registered trademark of Arysta LifeScience. Preemptor is a trademark of FMC Corporation.
©2016 BASF Corporation. All Rights Reserved. APN# 1604015 Southern Rust Biology and Management