Lifecycle insights as a prerequisite for targeted management of Cydalima perspectalis

The box tree moth (Cydalima perspectalis (Walker, 1859)), originally from Asia, has rapidly expanded its range in Europe, first detected in Germany and the Netherlands in 2007, likely via infested box tree (Buxus spp.) seedlings. In Croatia, the species was first recorded in 2012 in the Istria region. The larvae feed extensively on box trees, leading to defoliation and, in severe cases, plant death. This study, conducted on the Croatian mainland, focused on the development of first-generation larvae (n = 292) collected in April from the Garešnica region, just as they emerged from winter diapause. The pest development was monitored over six months, revealing that larvae resume feeding in mid-April and continue until late August before re-entering diapause. Degree day (DD) accumulation was tracked, showing that the first generation required approximately 560–640 DD to complete its development, while the second generation required 530–730 DD. Environmental factors, such as temperature, humidity and photoperiod, influenced larval development. Key periods for pest control were identified between late April to early May (when accumulated 53 DD) and late June to early July (when accumulated 478 DD), when larvae are in the early, more susceptible stages. Targeting larvae during these windows significantly reduced the second-generation population and minimized the number of overwintering larvae, which contributes to damage in the following spring. Understanding the lifecycle and environmental influences on C. perspectalis through degree day models is essential for optimizing management strategies and improving the timing and effectiveness of interventions to protect box trees from long-term damage.