Population dynamics of wheat and predatory thrips in winter wheat agrocenosis in the forest-steppe of the Samara region

Abstract

   The current paper has presented the three-year study results (2021–2023) on recording the population dynamics of wheat and predatory thrips during the spring-summer vegetation period of winter common wheat in the forest-steppe of the Samara region.   The purpose of the study was to determine the dynamics of the seasonal development of wheat and predatory thrips according to the phenophases of the development of winter common wheat in the forest-steppe of the Samara region.   For this purpose, there were carried out the calculations using the mowing method with an entomological net on winter wheat crops in different phenophases of development, and the population of species and thrips were determined in the laboratory under a binocular. According to weather conditions, 2021 and 2023 were characterized as dry and hot, 2022 was characterized as cool with plenty of precipitation in the first half of the winter wheat vegetation period. The population dynamics of wheat and predatory thrips varied depending on the weather conditions of the spring-summer period of the year. In the hot years of 2021 and 2023 there were 2 periods of increase in population. In 2021, the period of maximum population of wheat thrips was observed from a heading stage to a flowering stage (1016 and 1048 specimen per 100 sweeps of the net) and in the phase of milky-wax ripeness (426 specimen per 100 sweeps of the net). In 2022, the population of wheat thrips on plants increased gradually, the peak was noted once during the flowering stage, amounting to 1084 specimen per 100 sweeps of the net. In 2023, a population increase was observed in the heading stage (1782 specimen per 100 sweeps of the net) and the phase of milky-wax ripeness (421 specimen per 100 sweeps of the net). In the hot years of 2021 and 2023 there were 2 periods of increase in predatory thrips’ population; the maximum number of entomophages was observed during the heading stage and amounted to 87 and 61 specimens per 100 sweeps of the net, respectively. In the cool year of 2022, there was one population increase during the flowering stage and amounted to 14 specimens per 100 sweeps of the net. In the phases of heading and flowering of plants, there were predominantly adult insects (imago), and in the phases of milky and milky-wax ripeness, there were predominantly found larvae of different ages. The weather conditions in 2021 and 2023 turned out to be more favorable for the development of wheat and predatory thrips than in 2022.