The low-temperature tolerance of Cinara cedri (Hemiptera: Aphidoidea: Lachninae)

Cinara cedri is an economically important pest infesting cedars. This study presents the first study of its cold tolerance, providing key parameters for assessing its climatic adaptability and potential invasion risks. The supercooling points (SCPs) of eggs, adults, and first-instar nymphs (hereafter nymphs) were determined, along with lethal low temperatures, and the effects of cold acclimation (ACC) and rapid cold hardening (RCH) on cold tolerance. Results showed that eggs exhibited the strongest supercooling capacity, with a mean SCP of -30.14°C, significantly lower than that of adults (-12.89°C) and nymphs (-14.21°C). Under constant laboratory conditions, active aphids suffered no significant mortality at -5°C, whereas exposure to -7°C and -10°C for 1 and 2 h resulted in substantially higher mortality in nymphs than in adults. The 1- and 2-h lethal temperatures for 50% mortality (LT₅₀) were estimated as -10.28°C and -9.06°C for adults, and -8.00°C and -6.87°C for nymphs, respectively. Both ACC and RCH effectively enhanced cold tolerance; adults and nymphs exhibited markedly stronger cold hardiness in December relative to May, and exposure to 3°C for 2 h significantly reduced adult mortality. Collectively, these results establish an empirical foundation for forecasting population responses to short-term extreme low-temperature events and contribute to understanding the low-temperature biology of this aphid.