Pennsylvania Corn: Harvest Time Ailments

Corn ears infected with myotoxin and aflatoxin. Photo: G. Roth, Pennsylvania State University

A favorable corn growing season has transitioned into a challenging ripening time in many parts of the Commonwealth. Rains and persistent humidity over the last month have created a great environment for pathogens, even in those fields that have received fungicide treatments. With the impending harvest speeding our way, it is a smart time to scout fields and find out if your corn has any surprises waiting for you.

The first signs that your corn may be struggling is lodging and premature drying from the top down in scattered areas of a field.  The lodging becomes most apparent after storms with high winds, but early plant death may be more obvious earlier. These are both indicators of potential crown and stalk rots.  Some hybrids with purported resistance to stalk rots may still suffer from a low incidence of disease in a high-pressure year.

Resistance is more likely to be overcome in areas of a field that are prone to flooding or drought. When incidence seems randomly dispersed across a field, however, this may be due to genetic differences between the primary hybrid and the conventional hybrids necessarily included in “refuge-in-a-bag” type seed packages. The presence of stalk rots in a field is a good reason to move a field to the top of your harvest priority list to avoid further lodging and a difficult harvest for you and your combine.

Once you begin examining ears, you may find multiple issues stemming from our weather conditions.  Upon opening the husk, check for sprouting of the kernels.  Then, look for fungal growth on the ear that could be indicative of one or several problematic corn ear rots.  You will want to determine which fungi are involved and how much of your crop is affected because these diseases will not only affect yield, but also test weight and quality, since some can produce concerning mycotoxins.

Insect damaged ears will be prone to fungal infection and mycotoxin contamination. A field with significant levels of mycotoxins means you will have to make some critical harvest and storage decisions depending upon where that grain may be accepted and what it can be used for.

Finally, some areas of our state (Lancaster, Lebanon Counties) are experiencing high levels of the new leaf disease, tar spot, for the first time.  Be on the lookout for this disease as you scout your fields.  At this late stage, it is not a threat to most of the current crop, but the pathogen will likely survive in crop residue to cause problems next season.  It will be worth detecting the disease on your farm so you can prepare to fight it in the future.  Help us learn how far tar spot has spread this year by reporting any finds to us!

Harvest Time Corn Ailments

Corn affected by ear molds following damage. Image Credit: Adrianna Murillo-Williams, Penn State Extension

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