Curvularia leaf spot of corn
Curvularia leaf spot is caused by the fungus Curvularia lunata. The disease was officially reported in the U.S. for the first time in 2017 and has been observed in multiple states. Symptoms include small, tan-colored lesions with brown margins that may be surrounded by a yellowish halo. Lesions can be scattered across the leaf or in dense groups and can join together into larger necrotic areas. Lesions are often observed on leaves in the mid to upper corn canopy, but can appear at any growth stage. Symptoms of Curvularia leaf spot can look similar to those of eyespot. In general, Curvularia leaf spot has been considered to be more of an aesthetic issue than a yield-limiting disease in the United States.
The disease may be more common when corn follows corn, as it survives the winter in corn residue. Hot and humid conditions favor disease development. In addition, lesions tend to form on corn plants following rain that occurs during reproductive maturity.
Differences in hybrid susceptibility have been observed. Crop rotation and tillage reduce survival of the fungus. At present, foliar fungicides are not labeled for management of Curvularia leaf spot.
Characteristic Curvularia leaf spot symptoms on a corn leaf. Image: K. Wise
Curvularia leaf spot lesions can be surrounded by a yellow halo. Image: T. Allen.