As a cold front pushes through the corn-growing region in the next 24-36 hours, southwest winds to the east of the front along with scattered precipitation may serve as the necessary combination for isolated to scattered corn earworm flights. A Moderate corn earworm migration risk is predicted across the southern Great Lakes region tonight into tomorrow morning which includes far southeast Wisconsin and northeast Illinois, lower Michigan, northern Indiana and Ohio, and Ontario, Canada. The source region for the Moderate risk area is actually in Illinois so prospects for a shorter distance flight and increased moth catches is higher. Low risks extend back southwest into Illinois, Iowa, southeast Nebraska, Missouri, and Kansas where isolated flights are possible in weaker winds and less precipitation.
No risk is predicted Wednesday night into Thursday morning as high pressure builds into the Plains and northwest winds usher in cooler/drier air across much of the corn-growing region.
In the extended period, the overall weather pattern will become less progressive as Hurricane Irene moves up virtually the entire length of the eastern coast of the United States. Hurricanes act as blocking mechanisms to weather systems moving from west to east across the country so high pressure is expected to remain parked over the heart of the corn-growing region for much of the extended period. There may be some southerly flow way west in the Plains states and western Midwest by late week and into the weekend but the overall risk is low and crops are already past critical stages to insect damage in this area so only Low risks are predicted at this time.