Recently, Curvularia leaf spot of corn was confirmed in research and demonstration plots in Central Iowa, the furthest north it has been observed so far. This foliar disease is caused by the fungus Curvularia lunata and was first reported in the U.S. in 2017 and since then has been confirmed in Missouri, Louisiana, Kentucky, and now Iowa. Its effect on corn yield in the Midwest is unknown, but it can cause significant losses in tropical areas. It has not been reported in Ohio yet, but it is important to keep an eye out for this emerging corn disease during your late-season scouting efforts. Â Â
Especially in fields of continuous corn using conservation tillage practices, look for very small, round, tan lesions on leaves in the mid to upper canopy. Lesions have a white center with a water-soaked margin at first, then later develop an orange-brown margin surrounded by a yellow halo (Figure 1). Symptoms may be easily mistaken for other corn diseases such as eyespot or gray leaf spot. Eyespot is more commonly observed before pollination and under cool, wet conditions. Whereas the fungus causing Curvularia leaf spot requires warm, humid conditions. Early gray leaf spot symptoms may also look like Curvularia leaf spot, but gray leaf spot lesions will elongate as they develop, and Curvularia will stay round.
If you suspect Curvularia leaf spot, please submit a sample to the C. Wayne Ellett Plant and Pest Diagnostic Clinic (CWE-PPDC) located in Wooster, Ohio. See sample submission instructions on the CWE-PPDC website at https://ppdc.osu.edu/. You may also contact State Specialist Dr. Pierce Paul at paul.661@osu.edu (330-347-5878) or CWE-PPDC Director and diagnostician Dr. Francesca Rotondo at rotondon.11@osu.edu or ppdc@osu.edu (330-263-6721).