Farm Progress shared four experts’ advice on the best timing and management strategies for treating tar spot in corn.

According to Dan Ritter, Dairyland seed agronomist, tar spot usually peaks in September under ideal conditions. Treatment may be beneficial to protect stalk quality if the infestation is severe, but by mid-September, its impact on yield is minimal.

Brian Overstreet, soil conservation coordinator, recommends considering treatment before the R4 growth stage, especially if disease coverage is under 2%-3%. Post-R4, focus should be on early harvesting due to potential stalk weakness.

Steve Gauck, Beck’s agronomist, emphasizes the importance of early and frequent scouting, as tar spot can overwinter and affect future crops.

Dann Quinn, Extension corn specialist, notes that fungicide applications are likely needed if tar spot is detected before or during the R1 stage but are unnecessary if found at R4, as it won’t significantly impact yield. Once tar spot is present in a field, it typically remains, but its impact on the corn crop will depend on environmental conditions during the growing season, therefore, monitoring for tar spot in subsequent years is crucial.