In recent years, Crapemyrtle Bark Scale (CMBS) has continued to spread to new regions across the United States, including Washington D.C. and Florida. This invasive pest species not only threatens crapemyrtles, but also other important native plant species like American beautyberry (Callicarpa spp.) and Hypericum kalmianum L. (St. Johnswort). As a result, there is an urgent need to better understand the interactions between plants and insects and develop more effective pest management strategies. One of the major challenges in controlling CMBS is the difficulty in precisely characterizing its life cycle and population dynamics. This is due to the limitations of field observation and the small size of the early nymphal stages of the insect. However, recent research has made significant strides in addressing this issue through the use of laboratory studies and life table analysis.
In our recent studies, we constructed the first comprehensive life table for CMBS to characterize its biological parameters, including developmental stages, reproductive behavior, and fecundity (fig. 1). The study also examined the indirect effects of different Lagerstroemia hosts and plant nutrient conditions on CMBS populations. The demographic analyses revealed that different plant hosts and plant nutrient conditions had significant impacts on CMBS development and population dynamics.
The life cycle and population dynamics of CMBS were closely characterized on several Lagerstroemia species and cultivars, including L. indica, L. fauriei, L. indica × fauriei hybrids, and L. limii (figs. 2 and 3). Of all the tested crapemyrtle species or cultivars, CMBS populations showed the worst performance when reared on L. indica ‘Dynamite’. Although this is not conclusive evidence of insect resistance, our lab insect-rearing experiment demonstrated how CMBS would develop on L. indica ‘Dynamite’ when the inoculation level was relatively low compared to a natural setting (Xie et al., 2023). In a previous greenhouse trial, we found that the inoculation of CMBS could develop a relatively modest level of infestation on L. indica ‘Dynamite’. (Wu et al., 2021).
Interestingly, higher population growth rates and net reproductive rates were recorded under nutrient-deficient conditions, while CMBS reared on plants with healthier growing conditions had the most prolonged mean generation time (Fig. 3; Xie et al., 2022).
The biggest impact of the life table studies is the valuable biological and ecological data on CMBS that can be used to develop better and environmentally-friendly pest management strategies. The study provides insights into the life cycle of CMBS and how it is influenced by plant nutrient conditions. Understanding plant-insect interactions can help us identify host plant resistance and develop more effective pest control strategies.
Further research needs to be conducted to examine and compare the performance of CMBS on more host plants and how it can be managed under field conditions. The impact of plant defense mechanisms and the role of natural enemies in controlling CMBS populations should also be investigated. Overall, this study improves our understanding of insect biology and provides a foundation for further research to develop more effective pest management strategies.
References:
“Arkansas Crapemyrtle Database”, Cooperative Extension Service University of Arkansas System, https://www.uaex.uada.edu/yard-garden/resource-library/crapemyrtle/. Accessed 5 Apr. 2023.
“Lagerstroemia limii”, NC State Extension, https://plants.ces.ncsu.edu/plants/lagerstroemia-limii/. Accessed 5 Apr. 2023.
Texas Cooperative Extension, Texas Agricultural Experiment Station, Texas A&M University, and the Texas Nursery and Landscape Association. “Crape Myrtles for Texas”, Aggie Horticulture, https://aggie-hort.tamu.edu/databases/crapemyrtle/index.html. Accessed 5 Apr. 2023.
Wu, B., Xie, R., Knox, G. W., Qin, H., and Gu, M. 2020. Host suitability for crapemyrtle bark scale (Acanthococcus lagerstroemiae) differed significantly among crapemyrtle species. Insects, 12(1), 6. DOI: https://doi.org/10.3390/insects12010006.
Xie R, Wu B, Gu M, and Qin H. 2022. Life table construction for crapemyrtle bark scale (Acanthococcus lagerstroemiae): the effect of different plant nutrient conditions on insect performance. Scientific Reports, 12(1), 11472. DOI: https://doi.org/10.1038/s41598-022-15519-6.
Xie R., Wu B., Gu M., and Qin H. 2023. Biological Parameters of Crapemyrtle Bark Scale (Acanthococcus lagerstroemiae) Differ When Reared on Different Crapemyrtle Hosts. HortScience (in press).
