D3231: Establishment at low densities by crape myrtle bark scale

Since its detection in 2004, crape myrtle bark scale (CMBS), Acanthococcus lagerstroemia Kuwana (Hemiptera: Eriococcidae; (CMBS), has become well-established in the southeastern United States on crape myrtle (Lagerstroemia spp.), an abundantly-planted urban landscape tree. This sap-feeding pest decreases the aesthetic appearance and health of host trees, facilitating the colonization and development of sooty mold. We investigated a fundamental component of biological invasions- the minimum number of conspecifics requires for establishment – by inoculating trees with varying densities of CMBS and experimentally altering dispersal loss and predation effects by caging a subset of trees using fine mesh. Inoculum sizes as low as 1 ovisac per plant were able to successfully hatch and establish on potted crape myrtles, indicating that CMBS populations are not strongly affected by Allee effects at low densities. Establishment occurred on both caged and un-caged trees, and predation by ladybeetles and lacewings occurred in both treatments. Our results help to explain why CMBS has become widely established and indicate that, excluding negative effects from low genetic diversity, phytosanitation efforts may require extirpation of all females to be successful. Additionally, our results exhibit the influence of natural enemies on CMBS population dynamics, with the potential for further exploration regarding biological control.