Look at the picture taken in the Crop Watch 2015 field just a few days ago. Unlike some areas which are now drying out too much, this field continues to get rain- now in more moderate amounts. What it is doing is keeping moisture in the air. Due to early morning temperatures and the humidity in the ear, you can actually see the hazy atmosphere inside the plant canopy.
Crop Watch 8/17: Will field yield estimates be too high or too low this year?
Dave Nanda, consultant for Seed Consultants, Inc., says it's the stuff that foliar diseases are made from – excess moisture and enough warmth.
If you look closely you will see more than just a hazy morning with moisture hanging heavy in the air. You will also see leaves peppered with lesions. As the season progresses Nanda believes leaves will dry up, from the bottom up. What's troubling in this field is that lesions are already on leaves at and above the ear – that is the part of the photosynthetic factory you want to protect.
Why is disease so rampant? Nanda says the weather conditions have been near perfect in many cases. Second, the inoculum was there because of a large amount of disease present in many corn fields last year. This particular field was in soybeans in 2014, but inoculum can move in from nearby fields too.
The presence of the inoculum and good conditions for disease early helped the disease to an earlier start than in some years. When disease gets an early start and conditions remain "go" for disease, results can be devastating.
One option was selecting hybrids with good disease tolerance or resistance packages. Both of these hybrids in this field had good disease packages, but both are riddled with foliar disease. "If the disease pressure is super high, it can sometimes overcome the tolerance and set up shop anyway," Nanda says.
Fungicides are an option. Ironically, the farmer reports this field was sprayed right at or before pollination was well underway.
To be fair, this photo was taken in the first 20 rows from the outside of the field, located along a roadway. It's possible that the airplane operator didn't spray close enough to the power lines to cover these rows.
Next time we'll go deeper into the field where corn was spayed and assess the disease conditions at that point.