Source: Purdue University

After receiving multiple firefly reports in early May, it was not a surprise when early rootworm egg hatching was found on Tuesday, June 1 in west central Indiana. Judging by its size, it probably emerged sometime over the Memorial Day weekend, likely Saturday the 29th.

This date is just a benchmark and of little significance on its own. The key message here is that the rootworm egg hatch period is very prolonged (this is partially because eggs are laid at a variety of depths/temperatures), ensuring that whenever you plant, rootworms will be waiting for you. This year, the peak (highest activity) hatch will likely occur in mid-June. This underscores the fact that anyone still planting or replanting corn during the next two weeks should consider rootworm protection if they would typically do so.

Original press release