An active, fast moving weather pattern is expected to dominate the central and eastern United States as well as southern Canada over the next five to seven days. The result will be frequent cold front passages that will be preceded by southerly winds and possible precipitation that may lead to corn earworm flights and insect drop-out into portions of the corn-growing region.
A High corn earworm migration risk is predicted across southeast Minnesota, Wisconsin, northern Illinois, and northeast/eastern Iowa tonight into early tomorrow morning as a cold front moves through the heart of the corn-growing region. Southerly winds originating from source regions in the mid-south may carry corn earworm moths north into the central corn-growing region during this time period. As the front moves east, its parent low in Canada is expected to weaken so southerly winds will become less pronounced by Wednesday night into Thursday morning. Nonetheless, a Low risk is maintained from roughly I-57 east to near the Appalachian Mountains as some isolated or perhaps scattered flights occur into this region. A Low risk is also in place in the Plains as the next weather system and associated southerly winds may already pose a migration threat in that area.
Looking ahead to the extended period, the next weather system advances across the corn-growing region and upper Midwest. South to southwest winds are expected to the east of the cold front along with scattered precipitation. Crop stages in the source regions across the southern Midwest and mid-south are becoming less appealing as hosts with each passing day so corn earworm migration may occur more frequently even with a less than favorable weather pattern. As a result, Moderate risks are predicted for both Friday and Saturday nights mainly south of US 20 with Low risks into the upper and eastern Midwest as well.