European corn borer larvae are leaving their tell-tale early sign in local fields. Pin holes in your corn leaves like those in the photo below are an indication that the young larvae have started boring into the corn. The European corn borer is a tiny pest at first, but the worms grow quickly and can have significant impact on your corn. The introduction of BT varieties has reduced the corn borer populations in NYS significantly, but there are still occasional infestations. If you observe corn borers feeding in your BT hybrids, it's likely you have found the refuge corn. Conventional corn hybrids that do not have BT protection are susceptible to damage from this pest, which can result in weakened stalks and lodging, as well as creating entry points for diseases and ear and stalk rot. One local grower is using pheromone traps to assess whether a threshold population is present, informing the decision whether to spray.
For more information about European corn borer, see the Cornell Field Crops website at https://fieldcrops.cals.cornell.edu/corn/insects-corn/european-corn-borer/.