Western Corn Rootworm Hatch Update: Typical Timeline this Season

The annual western corn rootworm hatch appears to be similar this spring to the two most recent growing seasons. Thanks to Larry Bledsoe and his entomology colleagues at Purdue University, we have compiled a list of hatch dates over the past 20 years! Beginning on May 21 (and at 3-day intervals), Larry examined the root tissue of untreated corn plants for first instar larvae. On June 4 in Tippecanoe County, Indiana he found his first corn rootworm larva and estimated that hatch occurred the day before. As readers of this Bulletin know, saturated soils at the time of hatch can inflict significant mortality on corn rootworms. It remains to be seen how the heavy precipitation on June 7 across much of central and northern Illinois will affect larval survival.

Dates of Western Corn Rootworm Larval Hatch – Based upon Purdue University, Department of Entomology estimates.

  • 1996–June 12
  • 1997–June 13
  • 1998–late May (no precise date reported)
  • 1999–June 1
  • 2000–May 22
  • 2001–May 16
  • 2002–May 31
  • 2003–May 29
  • 2004–May 28
  • 2005–May 31
  • 2006–May 29
  • 2007–May 18
  • 2008–June 4
  • 2009–June 1
  • 2010–June 3 (second instars observed)
  • 2011–June 6
  • 2012–May 4–6 – Earliest observation of hatch by Larry Bledsoe in 35 years!
  • 2013 – June 4
  • 2014 – June 2
  • 2015 – June 3

As we move into late June, I anticipate the first sightings of western corn rootworm adults will begin to occur. Please share those observations with me and I will pass this information along to the readers of this Bulletin.

Mike Gray, Professor and Extension Entomologist