Weather conditions across Arkansas have been good for suppressing foliar diseases of corn. However, foliar diseases like common rust can be found at low levels of disease incidence and last week (June 4) a single corn plant with Northern Corn Leaf Blight (NCLB) was found by Michael Emerson in a field near Lake Village. Disease incidence and disease severity were less than 1% at this site, which was the only site NCLB was found though several fields were inspected in the area. This one site poses little threat to AR corn producers, but others sites may exist so producers are encouraged to monitor their fields for foliar diseases.
Northern corn leaf blight is caused by the fungus, Exserohilum turcicum, which can also infect grain sorghum and Johnson grass. Symptoms include a grey green cigar shaped lesions (Fig. 1) that are 3 to 15 cm long, they may become tan in color with dark zones of fungal sporulation. Spores called conidia (Fig. 1) are produced on these lesions under favorable conditions that are windblown to a new plant. Conditions that favor disease include dew or rain and moderate temperatures (65 to 80 F) for sporulation and conidia germination. When infection is delayed until 6 wk after silking yield loss is minimal in corn production.
There is no recommendation for AR corn producers at this time other than continue to monitor fields for diseases. Fungicides that suppress common rust and southern rust also suppress NCLB.