http://www.star-k.org/cons-vegdetail.php?ID=21
Corn on the Cob is kosher. The insects that may be infesting the cob are not. This hashgacha does not want to take the time to properly check (which is certainly their choice) the ears of corn for insects, or the store does not want to pay for someone to properly check. To state that the corn is not kosher is foolish, and false. They should have told you, we dont want to check for bugs (or, we’d rather not pay the mashgiach to do this because it isnt worth it) , so are not serving it at this time.