Diseases
Figure 1. Corn scouting calendar, shows diseases that could be causing the symptoms in the field. Individual descriptions of diseases, scouting and management strategies can be found in Chapter 16, Diseases of field crops.
Figure 1. Corn Scouting Calendar
(Disease calendar with links to various diseases in disease section below)
Seedling Blights
Anthracnose Leaf Blight
Northern Corn Leaf Blight
Eyespot
Bacterial Leaf Blight or Stewart’s Wilt
Grey Leaf Spot
Common Rust
Head Smut
Stalk Rots
Ear Moulds
Gibberella Ear Rot
Tar Spot
Fungicide Applications and Timing
Fungicide use in corn has increased significantly over the last decade. Most application timings focus on the VT (tassel emergence or early silk emergence stages). Earlier applications (e.g., 8 to 10 leaf corn) have generally been less profitable. Fungicide application for disease control should be based on scouting and presence of disease whenever possible. Producers need to ensure that their fungicide application timing and product selection are correct for their target disease. For example, certain fungicides and timings are suited for ear mould control and potential mycotoxin reduction, while others are prescribed for foliar diseases.
The price of fungicide application (product and application cost) and price of corn are generally the biggest factors in predicting the profitability of a fungicide application. Other factors that need to be considered include:
- disease pressure
- previous crop
- rainfall status
- hybrid susceptibility to diseases
For a more detailed discussion of fungicide use refer to Fungicide Use in the Chapter 16.