Biological Parameters of Crapemyrtle Bark Scale (CMBS; Acanthococcus lagerstroemiae) and the Plant-Insect Interactions Between Host Plants and CMBS

Abstract

Crapemyrtle Bark Scale (Acanthococcus lagerstroemiae; CMBS) is an invasive pest species that causes aesthetic and economic damage to crapemyrtles and poses potential threats to other horticultural crops in the United States. Recent reports have revealed the infestation of CMBS on the US native species, such as American beautyberry (Callicarpa spp.) and Hypericum kalmianum L. (St. Johnswort). Although previous studies reported this insect’s host range in its native range, the potential threats of CMBS to other documented alternative hosts and native species in the United States needs to be confirmed. Furthermore, previous knowledge regarding the biological parameters of CMBS, such as developmental stages and durations, population dynamics, and reproductive behaviors, remains elusive. To better understand CMBS as an invasive insect in the United States, we investigated its biological parameters by conducting insect feeding trials and life table studies under various conditions such as different plant nutrient conditions or different hosts.

Feeding preference studies of CMBS were conducted on forty-nine plant species and cultivars in 2016 and 2019, to gain insight into the expansion of CMBS distribution in the United States, as well as other regions of the world. The infestations of CMBS were confirmed on apple (Malus domestica), Chaenomeles speciosa, Disopyros rhombifolia, Heimia salicifolia, Lagerstroemia ‘Spiced Plum’, M. angustifolia, and twelve out of thirty-five pomegranate cultivars. In this study, we also constructed the first comprehensive life table for CMBS to characterize its biological parameters, including developmental stages, reproductive behavior, and fecundity. The indirect effect of three plant nutrient conditions (water, 0.01MS, and 0.1MS) and different Lagerstroemia species and cultivars on CMBS populations was examined using the age-stage, two-sex life table. The demographic analyses revealed that the plant nutrient conditions and different Lagerstroemia hosts had significantly altered CMBS development in terms of the intrinsic rate of increase (r), the finite rate of increase (λ), the net reproductive rate (R0), and the mean generation time (T). Overall, CMBS shows better insect performance when reared on plants under nutrient-deficient conditions in this study.