Calculating the theoretical expansion of European corn borer ecotypes in Europe and North-America using biological constants and abiotic conditions

The expansion of Ostrinia nubilalis Hbn. (Lepidoptera: Crambidae) was mapped with the help of its biological constants and climatological data based on a 55.8×55.8 km grid of ECMWF ERA-Interim dataset in Europe and North America in order to determine the tendency of the expansion of the ecotypes between 2003-2018. In the quest of visual mapping of voltinism of O. nubilalis, the yearly generation number was calculated at different points using the threshold temperature for the development and the accumulated degree-days. The examination highlighted that the northern limit of expansion of O. nubilalis can be attributed to latitude 58ºN in Europe. Besides, equally uni-, bi- and multivoltine ecotypes of the species were stably represented in Europe in the period under investigation, from which univoltine is the most widely distributed. Recent global warming and incidence of climate change favoured the appearance of the four generations of the multivoltine ecotype in southernmost parts of the Mediterranean Coast since 2014. O. nubilalis has stably developed four different ecotypes in North America during the period of 2003-2018. The most northern limit of development of this pest lies along latitude 50ºN, approximately in the middle of Saskatchewan (Canada ). Middle parts of the USA, including the Corn Belt states, were occupied by the bivoltine ecotype of O. nubilalis. The ecotype changing triggered by climatic fluctuation is mostly specific for the southern and middle areas of the USA, which can be explained by north-south relief exposure in North America. In summary, the northward expansion of the more generations of ecotypes of this serious pest may clearly cause increasing damage in maize-growing areas globally