Exploring indigenous entomopathogens for sustainable management of the invasive box tree moth (Cydalima perspectalis)

Abstract: The box tree moth (BTM), Cydalima perspectalis (Walker) (Lepidoptera:
Crambidae), is an invasive pest native to Asia that has rapidly colonized European boxwood.
The habitats in which this pest thrives significantly limits the application of chemical pesticides, as management in green spaces and forests necessitates precise, non-invasive interventions to preserve delicate ecological balances. Currently, authorized control options for C. perspectalis are limited, comprising natural pyrethrins, pheromones, and Bacillus thuringiensis var. kurstaki (Btk)-based bioinsecticides. However, none of these methods exhibit the required specificity or efficacy for optimal BTM control. To explore indigenous natural enemy populations of BTM for potential biological control programs, surveys were carried out in boxwood forests showing significant defoliation (80-90 %) in the pre-Pyrenean valleys of Navarra (Spain) from 2021 to 2023. Sampling was conducted during BTM field-outbreaks monitored by pheromone traps, including both overwintering (April-May) and summer (August-September) generations. A total of 3,481 larvae were collected from 61 locations and reared under controlled conditions (25 ± 2 °C, 60 % relative humidity, 16L:8D photoperiod) until death or pupation. In the 2023 survey, substantial incidences of entomopathogens were observed, with 6.3 % of 630 collected larvae displaying symptoms of infection by entomopathogenic fungi and 4.3 % developing baculovirus infection.