By Emmanuel Byamukama
Northern corn leaf blight (NCLB) was found in a few corn fields scouted recently. The disease was found at very low severity, except occasionally when an individual plant was found with several lesions on one leaf (Figure 1). The disease is characterized by long (1 to 6 inches) “cigar” shaped tan to gray lesions. The lesions have dark brown margin and can continue to expand in both directions over time.
Disease Cycle
Northern corn leaf blight is caused by a fungal pathogen Setosphaeria turcica (Syn. Exserohilum turcium). The pathogen overwinters in corn residue and is dispersed onto corn leaves by wind and splashing from rain (Figure 2). Under extended leaf wetness conditions (at least six hours) and warm temperatures (<81 F), spores germinate and disease development is initiated. The disease continues to develop throughout the season. Although spores of NCLB pathogen can be blown into the field, spores from corn residue within the field is the major source of the inoculum.
Figure 2. Northern corn leaf blight disease cycle. Source: Crop Protection
Management Strategy
Northern corn leaf blight is best managed by using resistant hybrids. Resistance to NCLB has been bred into most hybrids. Crop rotations and residue reduction can help in reducing inoculum but inoculum can also come from outside the field (blown in by wind). Susceptible hybrids with NCLB starting to develop at tasseling may benefit from a fungicide application. Several fungicides on market have good or very good efficacy against NCLB. A fungicide efficacy table for corn can be accessed
online. The fungicide efficacy table is produced by the Corn Pathology Working Group, in the Central region, of which SDSU has contributed data.