Be prepared to treat susceptible varieties with an insecticide if there are 6 or more beetles per 100 plants. Be prepared to act quickly - you need to look for these beetles when the plants are in the spike stage, just coming out of the ground. A banded application just over the plants should work. Keep scouting even after a spray, to make sure more beetles do not move in. The overwintering adults will feed on weeds and move into corn plants throughout May and June.
Beetles tend to be more abundant on outer rows.
Scouting on calm, sunny days works best - the beetles are most active then, and although they will jump away from you, it will be easier to spot them because of this activity. While a systemic may help, it cannot be totally relied upon. I am aware of one field in 1998 where the flea beetle was a significant problem even though a systemic soil insecticide was applied. A systemic insecticide applied at planting sometimes retains efficacy long enough to control flea beetles, but this is less likely if soil temperatures are cool or if immigration occurs over a long time. For example, if you have 7 days from planting to plant emergence, and then the beetles move in over a 3-week period, you would need the systemic activity to be maintained for a month, which is difficult.