Corn Leaf Diseases and Fungicide Reminders

  • Jul 22
    Greg Stewart
    Corn Leaf Diseases and Fungicide Reminders By Greg Stewart on July 22, 2016
    Categories: Grain Corn, Silage Corn

    Northern Leaf Blight

    • Most widespread of the diseases
    • Elliptical shaped lesions usually begin on lower leaves
    • Recent research shows an increase in races of this disease which bypass resistant genes
    • Significant yield impact when infection is high or begins early

     

    Common Rust

    • Does not overwinter in Ontario
    • Early symptoms are yellow flecks on either side of leaf
    • Commercial hybrids have good tolerance
    • Moderate yield impact

     

    Eyespot

    • Translucent yellow halo forms around infection – resembles an eye when held to sun
    • Sometimes confused with physiological fleck or insect damage
    • Economic losses due to eyespot are rare

     

    Gray Leaf Spot

    • Primarily exists in southwestern Ontario
    • Lesions are rectangular
    • Develops in lower leaves after tasselling
    • Most often associated with corn after corn and high residue
    • Moderate yield impact at current infection rates in Ontario

     

    Notes:

    • Fungicides are generally most efficient when applied at tassel stage and up to silk browning.  Applications that are earlier or later than these may not maximize the yield potential improvement.
    • Surfactants added to a fungicide application have been related to some pollination abnormalities, check with you supplier; products like Priaxor®, and Headline AMP® should not have surfactant added to the tank.
    • Only certain fungicides (i.e. Proline®, Caramba®) have shown to have any impact on reducing ear mould and vomitoxin levels, but timing is critical - silks must be emerged but not yet dried out.
    • Scouting and controlling Western Bean Cutworm may be significantly more important to reducing ear mould infection than a fungicide application.
    • If the timing works, an insecticide to control Western Bean Cutworm can be can be combined with a fungicide application.

     

    Greg Stewart
    Maizex Seeds Agronomy Lead

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