Abstract: Dioryctria sylvestrella, a stem borer, attacks the shoots, branches and cones of Pinus species, including Pinus sylvestris var. mongolica and P. koraiensis. To clarify the population dynamics, key regulatory mechanisms of this pest, and screen natural enemies for biological control in Heilongjiang Province, a two-year (2023–2024) field population life table survey was carried out on larvae and pupae, identifying the main lethal factors across developmental stages: overwintering, dehydration, pathogens, parasitism, predation, and natural death of larvae, and emergence failure, predation, and pathogens for pupae. Life table analysis showed the population growth indices were 9.01 (2023) and 11.19 (2024), confirming a significant upward population trend. Further combining the exclusion index of population control (EIPC), Morris regression analysis, and regression coefficient b-value analysis, the key regulators of its field population dynamics were larval overwintering and pupal emergence failure. To reveal the regulatory mechanism of larval overwintering, a low-temperature exposure experiment was conducted on 6th-instar overwintering larvae. After 1 h of low-temperature exposure, median lethal temperature (L_temp50) and L_temp99.9 were −23.3 °C and −30.2 °C, respectively; median lethal time (L_time50) was 10.9 days under constant of −8 °C, but 2.4 h under constant of −14 °C, confirming extreme low temperatures significantly restrict overwintering survival. Additionally, targeting pre-, mid-, and post-overwintering stages of 6th-instar larvae, the overwintering physiological basis was clarified: trehalose concentration was significantly higher in the mid-overwintering stage; glycogen was consumed in mid-overwintering, heat shock protein 70 (HSP70) increased significantly in mid- and post-overwintering, and sorbitol increased in post-overwintering. Five natural enemies were identified, Macrocentrus sp., Eriborus terebrans, Megarhyssa sp., Inocellia fujiana, and Orthrius striatulus. This study first identified the population limiting factors and overwintering mechanisms of D. sylvestrella, and screened its dominant natural enemies, providing theoretical support for regional green pest control.

Key words: Dioryctria sylvestrella, Dominant natural enemy, Exposure experiment, Lethal factor, Low temperature, Natural population life table