European corn borer biology & life cycle
The European corn borer (ECB) typically overwinter as fully grown larvae lodged in the stem or cob of the host plant, though they can also be found in other host plants such as large-stemmed grasses and various vegetables. Pupation occurs in early spring and adults emerge in early June to July. Larvae initially feed on the leaves and work their way to the whorl of the plant. Pinholes or shot holes are signs of borers already moving into the plant. Depending on the strain of ECB, growing conditions and the growing region, populations can go through one or two full generations and, in some cases, a partial third generation in a single season.