Effect of simulated temperature increase on the adaptability of emergent winter form of pear psylla Cacopsylla chinensis

【Objective】Temperature plays a critical role in insect growth and development, influencing key biological traits such as longevity, feeding behavior, and mating success. These factors, in turn, directly affect population dynamics and developmental trends. Pear psylla Cacopsylla chinensis, one of the major pests in pear, exhibits high sensitivity to temperature fluctuations. Notably, temperature variations also impact the growth and development of these host plants. The study aimed to better understand the effects of rising temperatures on the emergent overwintering C. chinensis (winter form of pear psylla) and its phenological synchrony with pear trees, and to clarify its occurrence and development trend under the background of global climate warming.【Methods】This study examined the effects of spring temperature elevation on the pear psylla by simulating pregermination phenological conditions of pear tree, under the condition of only providing dormant pear branches to pear psylla. The life span, pre-oviposition period, fecundity and egg hatching period of pear psylla under different treatment temperatures (5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃) were tested, the flower bud germination period of host pear tree under the same setting temperature were measured as well. The phenological correlation between the pear psylla and the host pear tree under different temperature conditions were analyzed. The developmental threshold temperature and effective accumulated temperature of flower bud germination, pear psylla oviposition and offspring hatching were studied by law of effective accumulated temperature method.【Results】Results showed that the life span of the pear psylla decreased significantly with the increase of temperature. At 50% mortality, the survival durations under different temperature conditions were as follows: 5 ℃ (24.16 d), 10 ℃ (18.05 d), 15 ℃ (7.25 d), 20 ℃ (7.56 d), 25 ℃ (5.80 d), and 30 ℃ (5.28 d). The average life span of pear psylla under 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃ and 30 ℃ were 47.09 d, 36.81 d, 18.50 d, 13.3 d, 10.12 d and 7.37 d, respectively. The duration of the pre-oviposition period of the pear psylla was significantly shortened with the increasing of temperature, the pre-oviposition period of the pear psylla were 47 d at 5 ℃, when the temperature ≥ 25 ℃, the pre-oviposition period were 3-4 d. 5 ℃ and 30 ℃ were unfavorable for the oviposition, the oviposition duration was 7 d to 9 d, the highest number of eggs was 93.5 at 25 ℃. The number of eggs laid ranged from 65 to 94, and there was no significant difference between 10 ℃ and 25 ℃. The duration of pear flower bud germination became shorter with the increase of temperature. When the temperature was less than 10 ℃, the time of flower bud germination was over 30 d. When the temperature was 15-20 ℃, the time of flower bud germination was similar, which ranged from 17 d to 19 d. When the temperature was higher than 25 ℃, it ranged from 7 d to 9 d. At ≥25 ℃, eggs exhibited the shortest incubation rate (10.67 d) and the highest incubation rate, indicating that this temperature was optimal for egg incubation. At 10- 20 ℃, egg incubation rate ranged from 13.33 to 30.33 d. At 5 ℃, the incubation rate was the lowest and the incubation duration the longest, demonstrating that 5 ℃ was unfavorable for incubation of the winter-form pear psylla eggs. The developmental threshold temperatures of the pre-oviposition, egg hatching, pre- oviposition and egg hatching, flower bud germination were 4.46 ℃ , 0.99 ℃ , 2.54 ℃ and 4.51 ℃, respectively, and the effective accumulated temperature was 115.25 days degree, 248.67 days degree, 368.51 days degree, 187.59 days degree, respectively. Through the curve fitting of the life span, pre-oviposition period, egg hatching, and the length and temperature required for flower bud germination of pear trees, it was found that their trends were consistent. The pre-oviposition period of pear psylla was consistently shorter than pear flower bud germination time across all tested temperature regimes. When the pear psylla oviposited, the pear flower bud did not germinate. When the pear psylla is close to death, it is the time of pear flower bud began to sprout. Egg of the winter form of pear psylla always hatched later than the germination of the pear tree, there is no shortage of food for the offspring. The oviposition-to-hatching period matched with pear flower bud germination time, ensuring offspring food availability.【Conclusion】Rising temperatures shortened the reproductive development period and life span of the pear psylla. However, higher temperatures also led to concentrated oviposition, decreased egg hatching time and a reduced oviposition period. When the temperature was above 20 ℃, it significantly favored the occurrence and reproduction of the pear psylla, and the damage they caused intensified. Additionally, elevated temperatures influenced the phenological development of the pear psylla’s host plants, accelerating the pear flower bud germination. Interestingly, the response of the pear psylla to temperature changes closely matched with the host plant, suggesting strong phenological synchrony with minimal disruption from temperature fluctuations. When nutritional resources for the overwintering pear psylla were depleted, the pre-germination of the pear flower buds allowed the pear psylla to replenish nutrients promptly. Alternatively, they could temporarily feed on non-host plants before reproduction. Notably, post-germination fertility of the pear psylla was significantly higher than that during the dormancy period, exacerbating damage to the pear trees. These findings would provide a theoretical basis for predicting population dynamics and improving pest management strategies against the pear psylla under climate change condition.