Foliar diseases present in most Mississippi corn fields
Scouting for corn diseases can be a daunting task. Looking out over the top of a corn field suggests that no diseases are present. This differs for the other crops we deal with where can observe a potential problem area and go to see what those problems might be whether it be shorter than normal plants or some other issue.
Foliar diseases are likely present in almost every corn field. However, with that said, the specific disease present as well as the field’s history likely dictates whether or not a foliar disease is present. Also, keep in mind, that certain corn diseases likely manifest themselves in corn that has passed the tassel stages. Most foliar diseases threaten corn as the corn gets closer to physiological maturity. For more information on the particular corn diseases that could be present see: http://www.mississippi-crops.com/2013/04/20/corn-disease-calendar/.
At present I have received only limited telephone calls regarding foliar diseases in corn fields throughout Mississippi, but as drier conditions have allowed more people to scout corn the call numbers have increased each day. Presently, I’ve observed the diseases outlined below and have also observed extremely low levels of southern corn leaf blight in one field in the south Delta.
Anthranose leaf blight
Over the past several weeks I’ve encountered anthracnose leaf spot. Normally speaking we don’t generally observe this disease, but the cooler and wetter conditions. In all of the cases I’ve observed this season the disease has been present on the lower leaves in the plant canopy. Lesions will generally be 3/4 of an inch in length to an inch in length. The lesions will not have parallel margins and most of the lesions may appear to have concentric rings, similar to a target. In addition, lesions may appear to have small pepper grains within the plant tissue that serve as the reproductive structure of the fungus. The disease can increase once tasseling starts, but rarely has an issue been reported with the leaf blight phase in MS. Typically the lower leaves on a corn plant are stressed and low levels of light in the deeper parts of the plant canopy allow the disease to increase on the bottom leaves of the plant. Management practices in the form of a fungicide are not necessary for anthracnose leaf blight.
Holcus leaf spot
Annually, calls/reports of Holcus leaf spot occur throughout the state. Holcus leaf spot is a fairly rare occurrence. Herbicide injury, urea burn, fertilizer burn, or even adjuvant burn associated with a foliar application are a more potential likely observation that widespread Holcus leaf spot. Even if Holcus leaf spot is present in a field at pre-tassel stages, or post-tassel for that matter, no management alternatives will reduce the symptoms associated with the disease.
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