With the “Bar Bell” deformity, kernel formation is normal at the base and tip of the ear but absent from the middle of the ear.
This problem is associated with chilling injury during ear formation and more evident in certain sweet corn genetic backgrounds. Low temperatures disrupt normal kernel development resulting in anomalous ear growth.
Barbell ears have been observed when non-GMO corn hybrids are sprayed with a low level of glyphosate in spray tank contamination at V5.
Avoid planting hybrids susceptible to this abnormality especially under conditions where cold temperatures during ear formation is likely.
Lipps, P. 2008. Personal Communication. Ohio State University.
Strachan, S.D. 2004. Corn Grain Yield in Relation to Stress During Ear Development. Crop Insights Vol. 14, no. 1. Pioneer Hi-Bred, Johnston, IA. Available at http://www.croppingcentralllc.com/pdf/resources/agronomy/corn/corn-yield-stress-ear-development-ci.pdf [URL verified 8/26/2019].