Most control methods focus on reducing populations of the beech scale, as Neonectria are unable to colonise trees that have not been previously infested with the scale. Thus control of Cryptococcus fagisuga is likely to slow the spread of BBD (Wiggins et al., 2004).
Cultural: Thinning and removal of infected or susceptible trees, while retaining resistant trees is a commonly used management strategy. This is important for decreasing long-term susceptibility and vulnerability of forests to beech bark disease. Potentially resistant trees can be identified by smooth bark and vigour. In contrast, large overmature trees, trees with rough bark, and trees with wounds, broken tops or other obvious problems are most likely to be infested by beech scale and most vulnerable to Neonectria infection (McCullough et al., 2003). However such practices not feasible in large areas of natural forest due to labour, financial and practical constraints (Wiggins et al., 2004).
Physical: Physical removal of scale insects by scrubbing trees, high pressure water, or use of petroleum-based oils, which cover and suffocate scale insects may be used on individual high-value ornamental or yard trees (McCullough et al., 2003).
Chemical: There is no practical chemical control for beech scale (Pond, 2008), although insecticides may be used for individual high-value ornamental or yard trees (McCullough et al., 2003). Herbicides may be used in some cases to control beech regeneration, in order to minimise root sprouting and the creation of dense beech thickets (McCullough et al., 2003). Pesticides are not acceptable control options in large natural areas because of labour, financial, environmental and practical constraints (Wiggins et al., 2004).
Biological: The most desirable option for control of BBD is a biological control agent of C. fagisuga (Wiggins et al., 2004). A number of natural predators and pathogens of C. fagisuga have been identified including coccinellids, mites, gall gnats and a fungus (Shingo, 1964 in Houston, 1994a; Wiggins et al., 2004; Dukes et al., 2009). However none are effective in stopping its spread to date (Pond, 2008), and much further research is required (Wiggins et al., 2004).
Genetic: An estimated 1% of American beech trees are resistant to scale insect infestation, and thus BBD. The cause of resistance to BBD remains unidentified (Koch et al., 2007), although in European beech resistance appears to be due to anatomical features that act as barriers to infestation (Lonsdale, 1983a in Houston, 2005), whereas in American beech resistance may be associated with less total and amino nitrogen concentration (Wargo, 1988 in Houston, 2005). Recent findings suggest that resistance to BBD ranges from partial to total resistance (Ramirez et al., 2007).
Currently the only known method to identify resistant trees is the artificial infestation method developed by Houston (1982). Drawbacks to this method include the minimum 1-year wait for results and the reliance on live scale eggs which could result in spread of the insect. Thus much research is focused on identification of genetic markers for resistance, trials to clarify modes of inheritance via cross-breeding resistant and susceptible individuals, and methods of propagation via somatic embryogenesis (Koch & Carey, 2005; Loo et al. 2005; Pond, 2008).
For a detailed account of management options for beech bark disease please read Management of Beech Bark Disease
2. Garnas R. Jeffrey, Matthew P. Ayres, Andrew M. Liebhold and Celia Evan, 2011. Subcontinental impacts of an invasive tree disease on forest structure and dynamics. Journal of Ecology 2011, 99, 532–541
3. Heyd, Robert L. 2005. Managing beech bark disease in Michigan. In: C.A. Evans, J.A. Lucas & Twery, M.J. (Eds) Beech bark disease. Proceedings of the beech bark disease symposium. Saranac Lake, NY, 16–18 June 2004. USDA Forest Service, NE Res Station, Gen Tech Rep NE-331. pp. 128-132.
4. Koch, Jennifer L. & Carey, David W. 2005. The genetics of resistance of American beech to beech bark disease: knowledge through 2004. In: C.A. Evans, J.A. Lucas & Twery, M.J. (Eds) Beech bark disease. Proceedings of the beech bark disease symposium. Saranac Lake, NY, 16–18 June 2004. USDA Forest Service, NE Res Station, Gen Tech Rep NE-331. pp. 98-105.
5. Koch, Jennifer L.; Carey, David W.; Mason, Mary E.; Nelson, C. Dana, 2010. Assessment of beech scale resistance in full- and half-sibling American beech families. Canadian Journal of Forest Research. 40(2). FEB 2010. 265-272.
6. Loo, Judy; Ramirez, M. & Krasowski, M. 2005. American beech vegetative propagation and genetic diversity. In: C.A. Evans, J.A. Lucas & Twery, M.J. (Eds) Beech bark disease. Proceedings of the beech bark disease symposium. Saranac Lake, NY, 16–18 June 2004. USDA Forest Service, NE Res Station, Gen Tech Rep NE-331. pp. 106-112.
8. Morris, Ashley B.; Small, Randall L.; Cruzan, Mitchell B., 2002. Investigating the relationship between Cryptococcus fagisuga and Fagus grandifolia in Great Smoky Mountains National Park. Southeastern Naturalist. 1(4). 2002. 415-424.
9. Pond, Sharon E. 2008. Conservation and propagation of American beech (Fagus grandifolia ehrh.) through somatic embryogenesis. Propagation of Ornamental Plants. 8(2). 2008. 81-86.
10. Wainhouse D. 1980. Dispersal of First Instar Larvae of the Felted Beech Scale, Cryptococcus fagisuga. Journal of Applied Ecology, Vol. 17, No. 3 (Dec., 1980), pp. 523-532
11. Wiggins, Gregory J.; Grant, Jerome F.; Welbourn, W. Cal, 2001. Allothrombium mitchelli (Acari: Trombidiidae) in the Great Smoky Mountains National Park: Incidence, seasonality, and predation on beech scale (Homoptera: Eriococcidae). Annals of the Entomological Society of America. 94(6). November, 2001. 896-901.
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