Influence of Temperature on the Autumn Population Structure of Rhopalosiphum padi (L.) in Western Poland

The bird cherry–oat aphid (Rhopalosiphum padi L.) constitutes approximately 70–80% of all aphid individuals found on cereal crops in Poland. It is considered one of the most economically important cereal pests, causing indirect damage through virus transmission and leading to substantial yield losses in agricultural crops. Previous studies have shown that the anholocyclic development of this species is strongly correlated with temperature patterns. Between 2018 and 2022, an analysis of the population structure of R. padi (gynoparae, males, and anholocyclic forms) was conducted during the autumn periods using a Johnson suction trap in Western Poland (Greater Poland region), in an area cultivated mainly with cereals. In years with a higher number of days characterized by mean daily air temperatures known to induce changes in R. padi biology, a marked decrease in the proportion of males within autumn populations was observed, along with a delayed onset of their occurrence. In each year of the study, temperature conditions conducive to the development of anholocyclic forms of R. padi were recorded. The abundance of individual morphs and forms of R. padi in autumn collections using the Johnson suction trap was distinctly variable and characterized primarily by a relatively low proportion of males in the catches (except for the years 2020–2021) within the total number of aphids of this species collected. An opposite trend was observed in these years regarding the proportion of anholocyclic forms of R. padi (2.61% of the entire population in 2020 and 3.51% in 2021).