Rotten to the cob: Western bean cutworm larval feeding damage and gibberella ear rot impact growers in Indiana

The western bean cutworm (Striacosta albicosta (Smith)), an established pest of dry beans and field and sweet corn, and the fungal pathogen, Gibberella zeae or Gibberella ear rot, are both pests that concern farmers in Indiana. Western bean cutworm is a relatively new pest species in the area, first trapped in Indiana in 2006. A native of the Great Plains, it has steadily continued an eastward colonization of the Corn Belt over the last decade. Gibberella zeae is a major fungal pathogen because it contaminates grain with mycotoxins, specifically deoxynivalenol and zearalenone. Livestock feed that contains these mycotoxins may lead to ailments affecting reproduction and general health. For example, in horses, the consequence of feeding mycotoxin-contaminated feed is death. Feeding damage from western bean cutworm larvae may exacerbate diseases within ears, especially fungal pathogens such as G. zeae. Although there are no fungicides labeled for control of ear diseases, growers apply fungicides to fields attempting to inhibit mold development. We conducted experiments on field corn during 2011 and 2012 to determine 1) the effects of western bean cutworm larval feeding on the development of G. zeae within husks and 2) the value of fungicide treatment in mitigating mold development. Plots with the combined factors of larvae and G. zeae spores had significantly more mold development than other treatments, suggesting that larval feeding damage does indeed encourage fungal growth within field corn ears. In regards to the application of fungicides, there was no significant difference between treatments inoculated with only G. zeae spores and those inoculated with spores with a fungicide application. These results imply that fungicide applications offer little protection in the management of ear rot diseases.