Corn: Rust (Puccinia sorghi)
Pub 812: Field Crop Protection
Guide >
Chapter
1: Corn > Rust
Field Crop Protection Guide 2011-2012, Order
2011-2012 publication
Table of Contents
- Description
- Integrated Pest Management Options
- azoxystrobin + propiconazole - Quilt
- azoxystrobin - Quadris
- pyraclostrobin - Headline EC
- propiconazole - Tilt 250 E, Bumper 418 EC
- prothioconazole - Proline 480 SC
- Related links...
Description
Early symptoms of rust infection are yellow flecks or spots on
either side of leaf. These develop into small, brick-red pustules
that break through the surface (epidermis). The brick-red colour
is the result of spores being released from these oval or elongated
lesions (2-10 mm (1-4 in.) long). Yellowing of the leaf occurs around
these lesions. Dead, brown (necrotic) areas of the leaf develop,
and in severe cases the entire leaf dies. The brick-red spores mature
and turn black as they mature, causing the lesions and leaf surface
to appear black.
Image 1. Common rust symptoms range from yellow
flecks to red pustules.
Integrated Pest Management Options
Rust is generally not a problem in Ontario except when infection
begins early in the season. Field corn has good resistance when
compared to seed corn, sweet corn, and specialty corn hybrids. As
a result, foliar fungicides in field corn are not needed unless
significant disease appears before corn tassels. Humid, cool conditions
favour the disease.
| Active ingredient |
azoxystrobin + propiconazole |
| Trade name |
Quilt |
| Rate per hectare (product) |
0.75-1.0 L per ha |
| Rate per acre (product) |
305-406 mL per ac |
| PHI* |
30 |
| Comments |
Ground and aerial application. Apply
when disease first appears, followed by a second application
14 days after, if environmental conditions are favourable for
disease development. Do not apply to field corn or field corn
grown for seed after brown silk. Maximum 2 applications/yr.
12-hr re-entry period. |
| Active ingredient |
azoxystrobin |
| Trade name |
Quadris |
| Rate per hectare (product) |
453 mL per ha |
| Rate per acre (product) |
183 mL per ac |
| PHI* |
7 |
| Comments |
Ground and aerial application. Apply prior to disease
development. Second application may be made 7-14 days later.
Maximum 2 applications/yr. Do not re-enter treated area until
residues have dried. |
| Active ingredient |
pyraclostrobin |
| Trade name |
Headline EC |
| Rate per hectare (product) |
400-600 mL per ha |
| Rate per acre (product) |
160-240 mL per ac |
| PHI* |
7 |
| Comments |
Ground and aerial application. For optimal
disease control, begin applications prior to disease development.
Use a minimum water volume of 100 L/ha. Do not graze treated
crop within 6 days of last application. Maximum 2 applications/yr.
12-hr re-entry period. |
| Active ingredient |
propiconazole |
| Trade name |
Tilt 250 E |
| Rate per hectare (product) |
500 mL per ha |
| Rate per acre (product) |
200 mL per ac |
| PHI* |
14 |
| Comments |
Ground and aerial application. Apply when
rust pustules first appear. Under severe disease pressure, a
second application 14 days later may be necessary. Only in seed
corn, under severe disease pressure can a third application
be made 14 days later. Can be tank-mixed with Ripcord or Matador
insecticide for insect control. |
| Active ingredient |
prothioconazole |
| Trade name |
Proline 480 SC |
| Rate per hectare (product) |
420 mL per ha |
| Rate per acre (product) |
170 mL per ac |
| PHI* |
14 |
| Comments |
Ground application only. Maximum 1 application/yr.
24-hr re-entry period. |
Related links...
