Western bean cutworm.
Western bean cutworm.

Western bean cutworm moth flights were monitored this season by many cooperators throughout Indiana. For eight weeks, late-June to mid-August, those numbers were posted in the Pest&Crop. The graph accompanying this article shows that moth captures were similar to last season, both years being low compared to the previous four years (2010-2013). Nonetheless, this pest has not gone away, even though subjected to some atypical weather since its first documented presence in Indiana in 2006.

This year offers a new dimension in the Western Bean Cutworm story. Several reports from field personnel in northern Indiana counties indicate large levels of damage to field corn ears, some still with western bean cutworm larvae in them. For most of these fields, the damage was unexpected because the Bt-traited hybrids have historically offered good protection against this pest. We have heard of similar reports in other North Central States and Ontario.  Expect to hear more on this in the future, as researchers try to confirm whether this is truly a case of resistance to the Bt toxin.

The Bt-protein must be ingested by the larvae before death by starvation occurs. So minor damage on the ear of Bt-expressing hybrids has long been recognized, usually as scarring/scraping on the tops of kernels. The type of feeding being found this year is much more severe, and larvae are not dying.