Significant Late Season Anthracnose Outbreak
By: Mike Toohill, AgVenture WSC
Bloomington, IL
As last week’s heat and humidity set in on the Midwest, yellowing corn fields (like my below left picture) became very common in my Illinois travels. Upon closer inspection, this field has significant Anthracnose Leaf Blight. This leaf blight (random yellowing followed by wilting) is often mis diagnosed as nitrogen deficiency (V-shaped yellowing of the older leaves starting at the leaf tips). Over the weekend Anthracnose Top Die Back has also become more common.
My experiences with Anthracnose: Over my 36+ years walking Midwest fields, Anthracnose (which survives in residue) is by far the most common corn disease complex in Illinois. This disease is favored by warm, humid weather and is very opportunistic (why it became so widespread as the corn crop encountered very hot and/or rapid soil drying conditions over the last week or so). In severely infected corn fields, ears can drop prematurely (around a 10% yield loss in my 50% milk picture). Under heat and/or moisture stress, entire fields with significant infection can die early. Unfortunate, but there is also an Anthracnose Stalk Rot.
What can you do at this point? It’s too late for a fungicide pass (except for maybe very late planted fields?) and even fungicide treated fields are most likely long out of “residual”. Hybrids vary widely on tolerance but heavy pressure can even overwhelm good genetic ability to fight this complex. My #1 suggestion is to closely monitor affected fields and harvest accordingly.
Harvest suggestions in fields with moderate to high Anthracnose pressure?
Although corn fields that die prematurely from this disease will not dry very well through the stalk and roots, this corn will air dry rapidly through the ear with the upcoming increase in temperatures. With expected field drying rates of ½ to ¾ point/day starting on Saturday, one needs to increase the pace on harvest preparations.
Hybrids/fields that have a higher % of plants that fail the “push” test should be prioritized for harvest.
With rapid dry down and high % of acres affected by this disease, I suggest that one starts at least a couple points wetter than normal. Why? Corn that dies from this disease almost always dries faster in the field (as long as it’s still standing) than anticipated and head fluff associated with diseased corn usually becomes problematic at moisture contents in the teens.
Finally, watch the weather forecast closely and not just the storms. In past years with heavy Anthracnose, I have seen dry fronts with wind wreck a lot of fields.
Have a safe harvest!
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