Identification, Life Cycle, and Presence of \u3cem\u3eNectria\u3c/em\u3e Species Associated with Beech Bark Disease in the Great Smoky Mountains National Park and the Effectiveness of \u3cem\u3eNematogonum ferrugineum\u3c/em\u3e as a Biocontrol

Two species of Nectria, N. galligena Bresadola and N. coccinea var. faginata Lohman, Watson, and Ayers, are associated with beech bark disease (BBD) in North America. In 1993, beech bark disease was discovered in the Great Smoky MOuntains National Park (GSMNP). Ten sites for permanent plots were selected for incidence of the disease at different elevations in the GSMNP. These plots were rated four times in 1994 and 1995 for the presence of two scale insects, Cryptococcus fagisuga Lindinger and Xylococculus betulae (Pergande) Morrison, and the presence of perithecia of Nectria spp. The beech trees in each plot were also rated for mortality, bark condition, and crown class. A significant negative correlation (-0.80691, p=0.0048) between the presence of Nectria spp. and the presence of X. betulae was observed, but no significant correlation was observed between the presence of Nectria spp. and the presence of C. fagisuga. Differentiation of Nectria spp. was accomplished morphologically and by ascopore measurement. Of the ten plots, four contained N. galligena, and five contained N. coccinea var. faginata. Both Nectria spp. were present at one plot, the Chimneys. Nectria spp. from two plots could not be identified due to nonviable ascospores. The life cycle of the pathogen was studied in the laboratory and in the field. Four trees, two at the Chimneys and two at Forney Ridge, were examined bimonthly from March 1994 to August 1995. In the field, perithecia were observed from March, 1994, through August, 1995, with the exceptions of February and April, 1995, when sites were inaccessible. Sporodochia were observed in the summer of 1995. The mycoparasite, Nematogonum ferrugineum (Persoon) Hughes (Gonatorrhodiella highlei A. L. Smith), was studied in the laboratory for its effectiveness as a biocontrol agent of Nectria spp. In examining the growth rates of N. ferrugineum and the Nectria spp. on 1% water agar medium, it was found that the mycoparasite grew twice as fast as the Nectria spp. An experiment demonstrated that a thin film of water covering perithecia of Nectria spp. prevented hyphal contact between N. ferrugineum and the perithecia. The results of another experiment established that N. ferrugineum did not produce substances toxic to Nectria spp