Source: OSU Extension Entomology
Symptoms:
Western Bean Cutworm (Striacosta albicosta) injury is characterized by feeding on ear tips or dime-sized holes in middle of corn ear. Injury is often associated with mold growth on affected kernels. Larvae of the western bean cutworm (WBC) are not cannibalistic, and may find >1 larvae per ear. Entry to ears is gained through silk channels or by chewing through husks, injuring the tip, base, and sides of the ear. Larvae feed on kernels until about mid-September, when they exit through husks.
Cause:
Kernel feeding by western bean cutworm tends to be restricted to limited parts of the ear. Partially consumed kernels may be further attacked by ear molds or secondary insect feeders that enter the ear through the cutworm’s feeding channel.
Management:
If 5-8% of plants sampled have either eggs or larvae, treatment should be considered. Repeated application may be necessary if adult flights continue through August. Many insecticides are labeled for WBC control, and timing of application should be after 95% of field has tasseled and before larvae enter the ear. See https://extension.entm.purdue.edu/publications/E-219.pdf for a list of labeled insecticides. Transgenic corn with Cry1F Bt gene (Herculex I, Herculex Xtra, Smartstax) or the newer Viptera trait has activity against WBC.
References:
Cook, K. 2005. Corn Earworm, European Corn Borer, Fall Armyworm, or Western Bean Cutworm: Which One Is Causing the Injury I’m Finding on My Corn Ears? The University of Illinois IPM The Bulletin No. 23 Article 4/October 7, 2005. Available at http://bulletin.ipm.illinois.edu/article.php?id=415 [URL verified 3/28/2019].
Cook, K. 2013 Western Bean Cutworm (Loxagrotis albiccosta). Available at http://ipm.illinois.edu/vegetables/insects/western_bean_cutworm/index.html [URL verified 3/28/2019].
Culman, S.W., A. E. Dorrance, R. B. Hammond, G. A. LaBarge, E. M. Lentz, L. E. Lindsey, M. M. Loux, A. P. Michel, H. E. Ozkan, P. A. Paul, L. H. Rhodes, R. M. Sulc, N. J. Taylor, P. R. Thomison, and H. D. Watters. 2014. Corn, Soybean, Wheat, and Alfalfa Field Guide. Ohio State University Extension Ohio Agricultural Research & Development Center Bulletin 827, Columbus, Ohio. Available at https://extensionpubs.osu.edu/corn-soybean-wheat-and-alfalfa-field-guide-pdf/ [URL verified 3/28/2019].
DiFonzo, C. 2018. Handy Bt Trait Table. Michigan State University. Available at https://aginsects.osu.edu/sites/aginsects/files/imce/BT%20Trait%20Table.pdf [URL verified 3/28/2019].
Michel, Andy, Celeste Welty, Ronald B. Hammond, and James B. Eisley. 2014. Western Bean Cutworm. Agriculture and Natural Resources Fact Sheet FC-ENT-40. Available at http://ohioline.osu.edu/factsheet/ENT-40 [URL verified 3/28/2019].