SUMMARY
Biological features of the development of the corn earworm in Ukraine are insufficiently studied. Therefore, the research conducted in 2017–2019 were the first attempt to describe in detail the phenology of the pest in the maize agrocenosis of the Left Bank Forest-Steppe of Ukraine.It was found, that the emergence duration of the corn earworm imagoes during the years of research lasted 46–52 days. The first butterflies on maize appeared in the first and third decades of June. The mass emergence of the phytophagous occurred in the second-third decade of July (the bloom period of maize). The seasonal dynamics of corn earworm imago in maize significantly depended on both the weather conditions of the growing seasons and the phases of crop development.The duration of development of the stages of eggs, caterpillars and pupae in 2017–2019 was 5.3, 31 and 20 days, at the sum of effective temperatures of 38.5, 243.6 and 147.0 °C, accordingly.In maize crops in the Left-Bank Forest-Steppe of Ukraine corn earworm developed during one generation, and the second generation was optional. Corn plants are damaged only by the first generation of phytophagous.For the development of the first generation of phytophagous, the sum of effective temperatures must be 590–610 °C at the development threshold of +15.0 °C, the duration of development is on average 61.3 days, at the average daily air temperature +21.6 °C.