Patterns of Egg Laying, Overwintering Survival, and Spring Hatch in the Green Apple Aphid (Aphis pomi De Geer) on Apple Trees

The overwintering biology of the green apple aphid (Aphis pomi De Geer) was examined over two years to quantify oviposition schedule, egg dispersion, survival, and hatch dynamics. Oviposition started from October, spanned 11–12 weeks peaking between late October and mid-November, with cumulative green eggs per shoot (30 cm long) averaging 385 in 2022 and 462 in 2023. Eggs were most concentrated on the second to fifth 10-cm shoot segments, and the gradient became less steep towards the termination of oviposition. Survival varied markedly among treatments: laboratory-stored shoots retained 63.6% egg viability, intact shoots 42.6–49.6%, and ground-excised shoots only 23.9–33.4%. Kaplan–Meier analysis showed a 73% higher hazard of egg mortality on ground shoots compared to intact shoots. Spring hatch commenced in early March and reached 100% by early April, with median hatch dates clustering around March 20–21. Cumulative egg hatch was found as more sensitive parameter for analysis of various effects. These results establish detailed phenological benchmarks and demonstrate that oviposition precision and overwintering success are strongly shaped by microhabitat and possibly plant status. The study represents the first comprehensive, data-driven investigation of this scale, providing robust parameters for temperature-driven forecasting models and informing integrated pest management strategies aimed at reducing early-season aphid establishment in apple orchards.