Mortality factors of Anoplophora glabripennis (Coleoptera: Cerambycidae) infesting Salix and Populus in central, northwest, and northeast China

Mortality factors affecting eggs, immatures (larvae and pupae combined), and adults of the Asian longhorned beetle, Anoplophora glabripennis, infesting Salix babylonica, Populus sp. (Section Aigeiros Duby), and P. gansuensis (Section Tacamahaca) were investigated in four Chinese provinces between 2015 and 2017. Immature density varied by location and tree species; however, overall density was highest in Jilin province. When immature density was compared between host tree species from the same province, nearly four times the immature numbers were found infesting P. gansuensis than S. babylonica. Although there were variations in mortality factors affecting different A. glabripennis stages between location and year, eggs appeared to be the most susceptible life stages to mortality factors compared to other life stages. On average, 59.3% of eggs were killed by undetermined factors (likely host tree resistance and microbial pathogens) across all survey sites and years. In contrast, immature stages were least susceptible to mortality factors, where on average 8.3%, 15.6%, and 9.1% of these were killed, respectively, by undetermined factors, woodpeckers, and unidentified predators across all survey sites and years. Parasitoids, Dastarcus helophoroides and Sclerodermus guani, were recovered from immatures in Gansu and Shaanxi provinces and Beijing City, together accounting for around 6.0% mortality of these stages in these sites. Across all survey sites and years, most longhorned beetle adults had emerged from their host trees; of the remaining adults (pharate) that did not emerge, 10.1%, were killed by undetermined factors, 8.1% parasitized by D. helophoroides, and >1% removed by unidentified predators or woodpeckers.