Dale et al. (2020) Evaluating the invasive potential of an exotic scale insect associated with annual Christmas tree harvest and distribution in the southeastern U.S. Trees, Forests and People 2, 100013. https://doi.org/10.1016/j.tfp.2020.100013

The movement of invasive species is a global threat to ecosystems and economies. Scale insects (Hemiptera: Coccoidea) are particularly well-suited to avoid detection, invade new habitats, and escape control efforts. In countries that celebrate Christmas, the annual movement of Christmas trees has in at least one instance been associated with the invasion of a scale insect pest and subsequent devastation of indigenous forest species. In the eastern United States, except for Florida, Fiorinia externa is a well-established exotic scale insect pest of keystone hemlock species and Fraser fir Christmas trees. Annually, several hundred thousand Fraser firs are harvested and shipped into Florida, USA for sale to homeowners and businesses. There is concern that this insect may disperse from Christmas trees and establish on Florida conifers of economic and conservation interest. Here, we investigate the invasive potential of F. externa on sixteen conifer species by quantifying the reproductive potential of this insect pest and its ability to establish, reproduce, and damage these plants. We find that small amounts of heavily infested Fraser fir plant material can release several hundred juvenile F. externa for over a month. Similar to other case studies, we find evidence that host susceptibility may in part be linked to phylogenetic relatedness. Encouragingly, only six of sixteen species evaluated were susceptible to attack. Our results provide new insights into methodology for evaluating scale insect dispersal and host susceptibility. We also provide guidance for future studies investigating scale insect reproduction, dispersal, and risk for plant species of unknown susceptibility to other exotic insect pests.