Incidence and Life History of Beech Scale, Initiator of Beech Bark Disease, in the Great Smoky Mountains National Park
Date of Award
Master of Science
Entomology and Plant Pathology
Jerome F. Grant, Mark T. Windham
Kristine D. Johnson, Charles D. Pless, P. L. Lambdin
American beech, Fagus grandifolia Ehrlich, in eastern North America are currently threatened by the devastating beech bark disease. This disease is caused by the fungal pathogens, Nectria coccinea var. faginata Lohman, Watson and Ayers, and Nectria galligena Bres., which infect trees that are predisposed by infestations of beech scale, Cryptococcus fagisuga Lindinger. In 1993, beech bark disease was discovered in the Great Smoky Mountains National Park (GSMNP).
In 1994, a 2-year cooperative research project involving the National Park Service and the University of Tennessee Agricultural Experiment Station was initiated to study several aspects of beech bark disease in the GSMNP. One objective of this research was to initiate long-term monitoring of incidence and distribution of beech scale and beech bark disease in permanent plots in the GSMNP. Additional objectives of this research included monitoring the life history and seasonal incidence of beech scale, and identifying natural enemies of this insect present in the GSMNP.
Permanent plots were established for long-term monitoring, and plots were sampled twice in 1994 and once in 1995 for incidence and levels of beech scale and Nectria supp. The overall status of beech scale has not changed dramatically in the permanent plots during this investigation. However, the overall incidence and levels of Nectria supp. have consistently increased during this study.
Permanent plots also were monitored in 1994 and 1995 for incidence of Xylococculus betulae (Pergande) Morrison, another scale species that has been associated with beech bark disease. This scale species was present in all permanent plots and at relatively high incidence in all but one plot.
Life history and seasonal incidence of beech scale were monitored at two locations in the GSMNP, from February 1994 to June 1995. During this investigation, the greatest number of beech scale eggs were collected in July and August 1994. The peak period for dissemination of beech scale occurred in September 1994, when the greatest number of crawlers were collected.
Few natural enemies of beech scale were observed in the GSMNP during this research. Monitoring for natural enemies of beech scale was conducted at four locations. Trapping for parasitoids of beech scale was conducted from May to September 1994, and no parasitoids were captured. Visual observations for arthropod predators of beech scale also were conducted from May to September 1994, and one predator, Trombidium sp., was documented to feed on beech scale.
The absence of parasitoids impacting beech scale populations, the limited diversity of predators of the scale, and the current success of this pest species indicate that beech scale will continue to threaten American beech in the GSMNP. Data from this research will provide base-line information needed for development and implementation of strategies for maintenance and control of beech scale in the GSMNP.
Vance, Robert Angelo, "Incidence and Life History of Beech Scale, Initiator of Beech Bark Disease, in the Great Smoky Mountains National Park. " Master's Thesis, University of Tennessee, 1995.