Cold hardiness and overwintering conditions of larvae of the Siberian moth, <i>Dendrolimus sibiricus</i> (Lepidoptera, Lasiocampidae) from Central Yakutia’s population

The Siberian moth, Dendrolimus sibiricus Tschetverikov 1908, is a dangerous pest of the conifer family Pinaceae that inhabits the Asian part of Russia, northern Kazakhstan, Mongolia, China and the Korean Peninsula. Its range is gradually expanding both westwards and northwards: the species is currently recorded at 46°–47° E over the Eastern European Plain, around 60° N in the Krasnoyarsk Krai and at 63° N in the Republic of Sakha (Yakutia). A number of studies have been devoted to predicting further dispersal of D. sibiricus, but the assessment of the pest’s invasion potential is hampered, among other things, by insufficient information on the requirements of the overwintering stage (larvae) to winter conditions. We evaluated the main features of pest biology, determined the cold hardiness of its larvae, and revealed the temperature conditions in the wintering places at the northeastern limit of its distribution in Central Yakutia. The average supercooling point of larvae was –18.5 ± 0.4°C, being significantly different (p ≤ 0.05) between individuals of younger (II–III and III–IV) and older (IV–IV) instars: –20.0 ± 0.6 and –18.8 ± 0.8°C, vs –16.7 ± 0.8°C, respectively. A prolonged (2 days) stay at –15.5°C leads to death of 53% individuals, 63% mortality at –17.5°C and already 91% at –20°C. Comparing larval cold hardiness and the temperatures in hibernation horizons in one of the coldest regions within the natural range of the pest shows suitability of large areas of Yakutia for D. sibiricus survival, especially currently due to climate warming.