Anthracnose Leaf Blight on Corn: Crop Disease of the Week at the U of I Plant Clinic!!

The sample of the week was Anthracnose leaf blight of corn!  The U of I Plant Clinic confirmed this fungal leaf blight on several corn samples.  As you can see in the pictures below, this disease is being observed at various corn growth stages. The fungus, Colletotrichum graminicola that causes Anthracnose requires wet and cloudy weather, which is just what the weatherman has ordered for the past several weeks.

Anthracnose leaf symptoms will vary among corn hybrids.  The lower leaves are usually affected first because this disease is lurking in corn residue, which means corn on corn is more at risk.  However, RESISTANCE is the key with this disease.  If you are seeing this in your field, I would check your hybrid's susceptibility to Anthracnose.  No need to worry too much at this time, if you are seeing this disease in your fields now.  Research has shown that this disease should not extend to far up the plant beyond the V6 growth stage.  Also, just because you are seeing Anthracnose leaf blight now, does not necessarily mean your corn has been sentenced to a stalk rot death.  So, fungicides are not warranted at this time.  For more information on Fungicides at Early Growth Stages, go to this link: http://bulletin.ipm.illinois.edu/article.php?id=1284

So, I think the underlying question on some of our client's mind was if this disease was killing corn seedlings, because many of our clients included a blighted corn seedling with their sample...just like the one below

Each of these blighted corn seedlings (like the one above) had roots that consisted of oospores, which tells me that our friend (or enemy), Pythium made it's debut on these roots and caused seedling blight or even death on many of the corn seedlings that were examined at the U of I Plant Clinic.  So, Anthracnose was not the culprit of the demise of corn seedlings.  In other cases, corn death occurred because corn roots were under water for a long enough period that caused root tissue to became oxygen deprived. 

Some of the older corn plants that I examined did show signs Pythium on primary roots, but I am very happy to report that new, healthy roots had grown and the corn was quickly "growing out" of the root rot, thanks to the recent onset of better growing conditions!

For more information on Anthracnose leaf blight, you can check out the following links:

http://bulletin.ipm.illinois.edu/article.php?id=1337
http://bulletin.ipm.illinois.edu/pastpest/articles/200211m.html