We had a lot of northern corn leaf blight and gray leaf spot fungal diseases last year in most of the Cornbelt states. They left a bunch of their inoculum behind on the ground.
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Cool and wet weather in June and continuing into July in some areas has been very conducive to the development of these pathogens. Some areas of the Corn Belt, especially in the Eastern Corn Belt, are already reporting early lesions of these diseases.
My guess is that the immense amount of inoculum from last year will find a way to infect corn plants at least in some parts of the Corn Belt with suitable environment especially on corn- after-corn ground. So, we need to be vigilant and prepared to protect our crops from these fungal diseases.
How do we decide if we need to spray and what is the best time to do so? Northern corn leaf blight can spread in cooler environment where as gray leaf spot likes high humidity and high temperatures. Minimum or no-till has also increased the incidence of many diseases.
Some popular corn hybrids on the market have very high yield potential but are very susceptible to certain pathogens which increase the probability of disease development. These susceptible but otherwise high yielding hybrids help in creating more disease inoculum for the following year since they are grown on a large number of acres.
You really don't need to use foliar fungicides on hybrids if they are resistant to the diseases present in your fields but you do need to scout your fields regularly where as others might have to be sprayed with the fungicides.
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Planting date and relative maturity of the hybrids can also affect the development of certain diseases. Earlier maturity hybrids can sometime escape the disease.
Nanda is a consultant with Seed Consultants, Inc. He writes from Indianapolis. Call him at 317-910-9876 or email [email protected]. He originally sent a similar version of this story to Seed Consultant staff.