Thermal summations are also highly predictive. Moths seek shelter during the daylight hours in dense grass and weeds near corn fields. Flushing moths from such habitats gives an estimate of population densities. Eggs can be sampled by visual examination, but this is a very time-consuming effort. Liquid formulations of insecticide are commonly applied to protect against damage to corn, particularly from the period of early tassel formation until the corn silks are dry.
Recommendations vary from a single application prior to silking, to weekly applications.
Liquid applications are usually made to coincide with egg hatch in an effort to prevent infestation. If corn borers are present in a field, however, the critical treatment time is just before the tassels emerge, or at tassel emergence from the whorl. This plant growth period is significant because the larvae are active at this time and more likely to contact insecticide. A popular alternative to liquid insecticides is the use of granular formulations, which can be dropped into the whorl for effective control of first generation larvae because this is where young larvae tend to congregate. Insecticide is more persistent when applied in a granular formulation.