The seedcoat on the crown of the kernel breaks open giving it the appearance of a partially popped popcorn kernel.
Unknown. Associated with irregular rainfall, especially when very hot and dry conditions are common. The injury may occur when very dry weather during grain fill is followed by a flush of rainfall, causing the endosperm to outgrow the pericarp. This kernel defect is often discussed in conjunction with silk cut. Generally popped kernels are regarded as an oddity that rarely occur in commercial hybrids in the Corn Belt and occasionally occur at significant levels in seed corn inbreds.
Scout fields to determine extent of this kernel injury. Harvest in a timely way and dry grain promptly. Provide good storage conditions (aeration, monitoring for mustiness, etc.). Market affected grain promptly.
Nielsen, R.L. 2010. Popped Kernels and Silk Cut. Available at http://www.kingcorn.org/news/timeless/SilkCut.html [URL verified 1/16/2019].
Vincelli, Paul, Chad Lee, and Ric Bessin. 2010. Some Unusual Kernel Injuries. Kentucky Pest News, Univ of Kentucky Extension.