The corn earworms are caused by a moth that lays eggs on the silks at night, especially after pollination and as the ears mature. When the eggs hatch, the mineral oil will smother the young worms. Many people mix BT (bacillus thuringiensis) with the oil for a higher worm kill percentage.
Sam, I think you mean the
silk instead of
tossel (tassel). The corn tassel is at the top of the stalk and develops pollen. Treating it will not reduce corn earworms. You have to treat the silks coming out of the ears just where they emerge from the shucks. Lots of people (me included) get tassels and silks confused at times.
BTW: Corn earworms are cannibalistic. That's why you normally only find 1 or 2 per ear. The moth lays lots of eggs that hatch, but the earworm that survives is the biggest one that can eat all its siblings.:laughing: