Predicted Seasonal Development of Phytophagous Forest Insects in the Temperate Zone

Abstract

In temperate climates, insects survive the winter in a coldinvulnerable stage. The timing of individual stages of insects is influenced by temperature (which will increase with climate change) and the photoperiod (which will remain unchanged). Therefore, the mechanical application of the sums of temperatures will not make it possible to predict the seasonal development of insects in the event of climate change. The aim of this paper was to assess a possible shift of the development of forest phytophagous insects with different types of seasonal development under climate change. Calculations are made for foliage-browsing insects in Kharkiv region (northeastern part of Ukraine). Temperature data were taken from archives and predicted temperature from reference. Our classification of foliage browsing insects by the types of seasonal development considering voltinism, hibernating stage, and summer diapause was used. The deadlines for the development of individual stages of insects were analyzed considering the type of seasonal development, the deadlines of the appearance after hibernation, and the termination of active development in autumn. The dependences of insect development from temperature were used. Analysis shows that the changes in the timing and rate of development of phytophages will depend on the type of seasonal development. Phytophagous species of the temperate zone, which are now monovoltine throughout the range, will remain so after global warming. Foliage-browsing species will accelerate the development of spring and early summer stages (before the summer solstice) and slow down the development of late summer and autumn stages, which will ensure the wintering of the most protected individuals. Foliage-browsing species capable of bivoltinous development within the current range will maintain this trend, but a further increase in the number of generations will be hindered by the photoperiodic response. Xylophages capable of bivoltine and multivoltine development can increase the number of generations. At the same time, due to the uneven development of insects in different parts of the tree and the stand, some individuals will hibernate in a stage that cannot withstand the cold.