There's still time for disease lesions to show up and for disease to develop. Is there time for it to become serious enough that it would warrant treatment?
That's a different question. The field is sporting ears with silks turning brown, indicating fertilization is likely over or nearly over. There are no lesions near the ear leaf where agronomists worry most about losing leaf area. Less leaf area at the top of the plant means less light can be intercepted and turned into sugars and starches that go into the ear.
The other issue is even if lesions are starting on lower leaves, but you determine it may not be a huge issue, is there time enough to spray fungicides? Or is it going to be too late for them to be effective?
Dave Nada, Seed Consultants, Inc., is surprised we've found few lesions in the Crop Watch field. And some other agronomists are reporting finding northern corn leaf blight and gray leaf spot. No one is yet talking about a major outbreak, however.
Nanda says cooler-than-normal temperatures and plenty of moisture favor a disease like northern corn leaf blight more so than gray leaf spot. If it warms up and temperatures run normal to above normal with ample moisture, then gray leaf spot could become more of a concern, he notes.
So if you're still on the fence about fungicide decisions and your field looks like corn in the Crop Watch '14 field, it's time to jump off the fence. Which way you jump, either to spray or not spray, ought to be based upon what you're seeing in the field, what you know about susceptibility of the hybrid in fields where you find lesions, how close they are to the ear leaf at this point, and how quickly your dealer could make the application.
You will also want to know what the label says about the product you choose to apply in regards to timing of application.