The seasonal development of the European corn borer,Ostrinia nubilalis(Hübner) was studied in the Hudson Valley of New York from 1973 through 1975 in relation to the phenological events of selected woody and herbaceous perennial plants. Adult occurrence periods—the initiation of 1st brood flight, peak 1st brood flight, approach of inter-brood, initiation of inter-brood, initiation of 2nd brood flight and peak 2nd brood flight—were selectively correlated with various phenological events of 10 plant species. General relationships among phenological events of 14 plant species and 6 pupal occurrence periods were also found. Observance of the phenological events should forecast the occurrence of each European corn borer period in areas of the Northeast where the indicator plants and insect occur together.