When moth activity is evident, sampling usually begins when the earliest fields reach the early whorl stage of plant development. For fresh market whorl-stage sweet corn, information gathered during sampling should include the number of egg masses as well as live larvae. During the whorl stage, inspect the whorl leaves of 100 plants per 20-acre field and record the number of egg masses when appropriate. Samples should be taken in 10 locations in a field and at least 100 feet inside the field to avoid border area influence. Sampling should consist of examining five consecutive plants in one row, then five more plants in the adjacent row. When sampling for egg masses, the underside of leaves should be examined. It is important to determine if larvae are present and actively feeding. Pull out and carefully unroll the whorl leaves and tassels of the first two plants showing damage at each field location; note the number of plants with live larvae.

During the period when tassels are emerging from the whorl, inspect only the tassels and record the number of plants that have live larvae feeding on the tassels. If fall armyworm (photo) is present, add the number of plants infested with this insect to the European corn borer assessment; a management decision must be based on the combined infestations of both insect pests.

The time to spray silking fresh market sweet corn is determined by the number of moths captured in blacklight traps and by the extent of egg laying and larval feeding during the presilk stages of corn development. Direct sampling for the European corn borer and other ear-damaging insects during the tasseling and silking periods of fresh market sweet corn is marginally effective because of low economic injury levels. Consequently, treatment is based on moth captures or evidence of infestation in adjacent younger corn plantings.