D3258: Development of predictive model for egg hatching of Korean population of Asian spongy moth, Lymantria dispar asiatica (Lepidoptera: Erebidae)

The Asian spongy moth is a destructive forest pest in its native regions, and is also considered as a significant quarantine pest in non-native areas. The complex dynamics of its egg development, encompassing pre-diapause, diapause, and post-diapause stages, making it challenging to accurately predict timings of egg hatching and the emergence of second instar larvae, which are critical stages for effective management. In this study, we investigated the characteristics of temperature-dependent development for overwintered egg populations of Asian spongy moth in Korea. The post-diapause populations were exposed to six constant temperatures (8, 13, 18, 23, 28, and 33 °C). The lower development threshold temperature of the overwintered egg population was estimated to be 3.23 °C, with a thermal unit requirement of 350.89 ± 43.049 degree days (DD). Egg hatching were then estimated using an individual-based simulation, incorporating the estimated thermal requirements of overwintered eggs. The simulation results, generated by 10,000 individuals, closely matched with the distribution of egg hatching time observed in actual field conditions. We subsequently fine-tuned the parameters of the existing GLS model, initially developed to predict the phenology of the spongy moth, to better represent the egg hatching patterns of the Korean population. We also proposed a stable starting date for accurately estimating egg hatching in the Korean population. Our findings could serve as a useful tool in determining optimal sampling timings for pest control, and ultimately aiding in risk management against the undesirable attachment of egg masses on shipments in port areas.