Hurricane Irene is expected to be a significant hindrance to corn earworm migration in the corn-growing region as broad northeasterly flow on the west side of the hurricane envelops all growing areas mainly east of the Mississippi River. Further west, high pressure is expected to hold firm in the Plains until the hurricane moves into the maritime provinces of Canada by early next week. Therefore, with a lack of any organized southerly wind, no corn earworm migration risk is predicted through Monday morning.
As high pressure edges east by early next week, southerly winds will eventually return to the Plains and western Midwest. A Low migration risk is predicted west of US 71 and south of I-90 for Monday night, or from southern South Dakota into Nebraska, western Iowa, and Kansas. The risk area expands to the east quite dramatically for Tuesday night and Wednesday morning as a cold front pushes into the Plains and high pressure advances off into the eastern United States. A broad Low risk area is predicted from I-57 (eastern Illinois) to the west and includes virtually all field sites as far north as southeast North Dakota, northwest Minnesota, and into northern Wisconsin.