Joe Spencer, an entomologist with the Illinois Natural History Survey, observed 2nd and 3rd instar corn rootworm larvae June 23 in his research plots located north of Urbana, Illinois. He anticipates the emergence of adults from these plots by early next week. As we begin the 4th of July Holiday, I suspect initial sightings of western corn rootworm adults will begin to occur across central Illinois. Overall, I anticipate the statewide population of western corn rootworms to be reduced this season due to the heavy precipitation many areas have received throughout June leading to saturated soils at the time of larval hatch.
On June 11, 2015 I observed a few Japanese beetles in cornfields scattered across western and central Illinois counties. In recent years, densities of this pest have been most significant in northwestern Illinois. If you begin to observe western corn rootworm adults in your area of the state, please let me know and I will pass along your observations to readers of this Bulletin.
Source: Mike Gray, Unversity of Illinois