Of course, the answer to this question depends on several things …..

1. Do you have a problem?  Most areas are NOT experiencing a substantial second-generation flight of southwestern corn borer moths (or European corn borers).  The odds are good that spraying blindly, without any moth trap or scouting data, will not pay.
2. How mature is your corn?  Corn that started tasseling 3-4 weeks ago will be much less susceptible than corn that has begun tasseling in the last two weeks.  Insecticide treatment is typically not recommended once corn reaches the dent stage.
3. What about the weather?  Although the value of fungicide application in drought stressed corn is undoubtedly reduced, the effects of corn borer feeding will have more impact on drought and heat stressed corn.  Their tunneling interferes with water and nutrient flow, and thus, worsens the impact of drought.  Well watered corn can better tolerate corn borer injury.