See the cob lying on the ground? See the black spot? That's a baby corn borer. We scanned our ears for two signs of borer damage when we picked them. I was disappointed to see these signs on two of the four ears I brought home for dinner.
1) Worm hole in the husk
2) Frass (usually on the stalk end)
It actually isn't a big deal at all. I just cut them out.