Humidity modulates the effects of high temperature on the thermal tolerance of 4 aphid species

Accurate prediction of aphid population trends depends on understanding the characteristics of aphids' responses to high temperature and humidity. Currently, most studies on the interactive effects of high temperature and humidity on aphids focus on a single species, and whether multiple species exhibit similar response characteristics warrants investigation. This study examined the effects of combinations of temperatures (38 °C, 42 °C) and relative humidities (20%, 60%, and 90%) on the mortality and heat tolerance (characterized by LT50) of Myzus persicae (Sulzer, 1776), Acyrthosiphon pisum (Harris, 1776), Sitobion avenae (Fabricius, 1775), and Aphis craccivora Koch, 1854. Results showed that low relative humidity (20%) generally enhanced heat tolerance in aphids, although in some species, temperature combinations, the effect of humidity was not statistically significant. In contrast, high relative humidity exacerbated mortality under high-temperature conditions. Additionally, different aphid species exhibited species-specific responses to changes in temperature and humidity. A. craccivora showed the highest heat tolerance among the species tested. This study identified the temperature-humidity synergistic effect as a key factor regulating aphid survival and provided ecological insight for predicting aphid populations and formulating adaptive management strategies under climate change.