The Sevin is really bad stuff - very toxic to honeybees and other beneficial insects, toxic to aquatic animals when the run off gets in to streams, not very good for you or your pets. It is banned in most other countries. Here's a thread where we talked about it more, with links to some info:
https://www.helpfulgardener.com/forum/vi ... p?p=137879
I agree with potatoes that it would be rare for ants to attack corn that was undamaged. They mostly go for dead or decaying stuff, over ripe stuff and stuff that has already been injured. The likeliest pest to cause the kind of damage you are talking about is the corn earworm. Look carefully to see if that is what you have. Corn earworms do eat the silks before entering and attacking the tips of corn.