Characterization of Cold Tolerance of Immature Stages of Small Hive Beetle (SHB) Aethina tumida Murray (Coleoptera: Nitidulidae)

Simple Summary Establishment and distribution of invasive insects depends on their cold tolerance especially in temperate regions. The small hive beetle (SHB) is native to Sub-Saharan African countries, from where it has now invaded all over the world, including South Korea as a destructive pest of honey bees. Therefore, the present study first time provided information about the survival and adaptation capacity of immature stages of SHBs to tolerate the cold environment. All tested immature stages: feeding larvae, wandering larvae and pupae of SHB were sensitive to chilling injuries. However, wandering larvae and pupae showed substantially enhanced survival in cold lethal temperatures after acclimation, but not the feeding larval stage. This plasticity of cold tolerance in wandering larvae and pupae could contribute to the winter survival of the SHB population for better establishment and range expansion in temperate regions such as in Korea. The small hive beetle (SHB) Aethina tumida Murray, (Coleoptera: Nitidulidae) is now a global invasive pest of honey bees, but its cold tolerance potential has not been yet explored. Therefore, we measured the supercooling point (SCP) of different stages of SHBs and also the impact of acclimation on their SCPs and survival as a measure for cold tolerance. Combinations of different temperatures (0, 3, 5, 7, and 10 degrees C) for different hours (1, 3, 5, 7, 12, 24, 35, and 48 h) were used to assess SHB survival. The supercooling points occurred at lower temperatures (-19.4 degrees C) in wandering larvae than in the other stages (pupae: -12.5 degrees C, and feeding larvae: -10.7 degrees C). A lethal temperature (LT50) of feeding larvae was achieved earlier at 4.9 degrees C after 7 h exposure than the wandering larvae (3.7 degrees C at 48 h) and pupae (5.6 degrees C at 48 h). The sum of injurious temperature (SIT) is the most suitable estimation to describe cold resistance of the SHB immatures. The wandering larvae were the most cold tolerant, followed by pupae and feeding larvae based on SIT values of -286.8, -153.7 and -28.7 DD, respectively, and also showed more phenotypic plasticity after acclimation than feeding larvae and slightly more than pupae. Our results show that all stages, i.e., feeding larvae, wandering larvae and pupae, are chill susceptible. However, these stages, especially wandering larvae and pupae, showed the capacity to acclimate to cold temperatures, which may help them to survive in winter for the continuity of the SHB population, especially in a scenario of climate change.

Automated summary

The present study focused on the cold tolerance of small hive beetles (SHB) in temperate regions, finding that wandering larvae and pupae displayed enhanced survival in cold temperatures after acclimation, contributing to their potential to establish and expand in regions like Korea. The study measured supercooling points of different SHB stages, with wandering larvae showing the lowest supercooling point and highest cold tolerance. Additionally, the results demonstrated that all stages of SHB are susceptible to chilling injuries but have the ability to acclimate to cold temperatures, potentially aiding in their winter survival and population continuity amidst changing climates.