Bobert- "Organic: Apply 5 drops of mineral oil, corn or soybean oil (apply only once) to corn ear tips when the silks begin to turn brown not before because the oil will interfere with pollination. If the eggs and larvae survive this barrier, use a knife to cut off affected parts of the corn before cooking. The remaining ear of corn will be clean and edible. "
http://www.caes.uga.edu/extension/floyd/anr/documents/HowtoKeepCornEarwormOutoft