South Carolina: Pee Dee Corn Needs Rain, New Disease Showing Up

Photo: Justin Ballew, Clemson University

This has been a warm and dry week and our corn is really showing it right now.  Most dryland fields are rolling up like in the photo below.  There is a good chance of rain in the forecast this weekend and we really need it.

Most of our corn is in the R5 stage where the moisture content in the kernels is decreasing.  Water stress at this time can lead to lower kernel weight (test weight).  The ear pictured below is a little past 1/4 milk line (R5.25), so it will have just under 30 days until it reaches physiological maturity, or black layer.  If the next 30 days continue to be as dry as it was this week, we may see some poor test weights.


Corn at R5.25 (1/4 milk line).

Earlier this week, Clemson Grain Specialist David Gunter sent out a notice about a new corn disease that is showing up in parts of SC called Physoderma brown spot.  In the places its been found it is reported to be fairly serious and requires a fungicide treatment to hold it in check.


Physoderma brown spot on corn leaf. Photo from David Gunter.

Physoderma brown spot has been observed on leaves and stalks and can compromise stalk strength and cause lodging.  This fungal disease is believed to survive in the soil and on plant debris, so fields that are corn behind corn should be the first ones that we scout for this.


Physoderma brown spot on corn leaf. Photo from David Gunter.


Severe Physoderma brown spot infection. Photo from David Gunter.

We really need to be out there scouting and if any Physoderma is found, a fungicide may be necessary if that particular field is not past the R5.5 stage (1/2 milk line).  According to David Gunter, the fungicides typically used for rust are probably our best options, if needed.  Pay close attention to pre harvest intervals on fungicides if you decide to use one this late in the season.

Fungicides labeled for disease control on corn can be found in the UGA Pest Management guide on pages 62-63.

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