As corn began to tassel in the beginning of August, many fields contained Northern Corn Leaf Blight (NCLB) lesions. As of today, most fields are showing minimal signs of progression; however, heavy dews, high humidity and moderate temperatures are ideal for disease progression. In worst cases, the entire leaf will become blighted.  Early infections with favourable environments can cause yield loss upwards of 50% (Albert Tenuta – Ontario Grain Farmer, January 2014).  Below is a photo taken as a grower opened up his field for silage in 2013. The left picture had no fungicide, while the right was sprayed at tassel.

Call to action

Scouting regularly is the best action item for today. If you start to see the progression (brown lesions getting bigger & merging together or moving up the plant to the ear leaf or higher), you still have an opportunity to spray a fungicide to protect your existing green tissue.  When spraying outside the optimum target stage (tasseling), the yield boost has disappeared; however, the priority now is to protect the yield you have. In Lambton County, we need to keep the upper canopy green for the next 45 days. Upper canopies that go brown before Oct 15th will have yield loss. You still have options to protect yourself – don’t let your guard down!

Kirk Van Will, CCA-ON, Maizex Seeds Yield Specialist, West Middlesex & Lambton Counties
Twitter: @KirkVanWill