I don’t remember if it was Carey Reams or William Albrich who said that the insects are nature’s garbage collectors. In other words if you want to stop the pests you need to grow a healthier crop. What is your current fertlizer program? What type of corn are you growing?

If I had to guess I would imagine you corn either has too much nitrogen and/or is lacking a necessary micronutrient to form more complex sugars and amino acids.