Beech bark disease of American beech (Fagus grandifolia) is caused by the interaction of an introduced scale insect (Cryptococcus fagisuga) and the native fungus Nectria galligena, or N. coccinea var. faginata, which is thought to be introduced. Infestations of the insect precede development of the disease, and N. galligena is often found before N. coccinea var. faginata. Previously published records indicate that the beech scale extends as far west as eastern Ohio (2) and southern Ontario (Sajan, personal communication). The scale is now well established in several locations in both the Upper Peninsula (UP) and Lower Peninsula (LP) of Michigan. The scale insect has been found in beech stands throughout three counties (Oceana, Mason, and Muskegon) along the Lake Michigan shore in the LP, extending for at least 100 km from north to south, and occurring up to about 80 km inland. In the eastern UP, beech scale has been found in four counties (Alger, Chippewa, Luce, and Schoolcraft). The heaviest beech scale infestations are distributed around Ludington State Park in the west central LP and the Bass Lake Forest Campground in the eastern UP. The extent of the insect infestation suggests that it has been present in Michigan for many years, with anecdotal accounts placing the first observations of beech scale at Ludington State Park around 1990. These infection centers are distant from previously known beech scale infestations and are located in heavily used recreation areas, suggesting that the insect may have been transported by human activity. Perithecia of N. coccinea var. faginata were found in Ludington State Park in the LP at N 44° 1.951', W 86° 29.956' and perithecia of N. galligena were found at the Bass Lake site in the UP, at N 46° 27.748', W 85° 42.478'. The identity of the fungi collected from each location was confirmed by measurements of perithecium and ascospore morphology (1). Perithecia at both sites were scarce and difficult to find. Surveys planned for the summer and fall of 2001 will further delimit the occurrence and distribution of the pathogens involved in the disease in Michigan. To our knowledge, this is the first report of the beech scale and beech bark disease in Michigan, with N. galligena and N. coccinea var. faginata identified as the pathogens. References: (1) H. V. T. Cotter and R. O. Blanchard. Plant Dis. 65:332-334, 1981. (2) M. E. Mielke et al. Plant Dis. 69:905, 1985.

Butternut (Juglans cinerea) is being killed throughout its range in North America by Sirococcus clavigignenti-juglandacearum, a fungus of unknown origin causing multiple branch and stem cankers that eventually girdle infected trees (USDA Forest Service 1993). Sprouts, if they develop, are also infected and killed usually within the first few years. The fungus was described as a new species in 1979 (Nair et al. 1979) and only butternut is known as its natural host.

Seventy-nine plots in Illinois, Iowa, Missouri, and Wisconsin were surveyed in 1990 for ash yellows (AshY) and other diseases and insects. Twenty-one of 38 white ash and 20 of 41 green ash plots had trees with AshY based on the 4',6-diamidino-2-phenylindole (DAPI) DNA-staining technique or the presence of witches-brooms. AshY was widely distributed in all states except Wisconsin, where trees in only two of 20 plots were affected. Other than witches'-brooms, symptoms previously associated with AshY were present on trees in plots that tested both positive and negative for mycoplasmalike organisms. Approximately 50% of the ash trees had greater than 10% crown dieback, and 5% of the trees were dead. Overall, trees representing about 12% (6-7 m3.ha-1) of the total ash volume had 50% or greater crown dieback. There was no significant difference in mean crown condition rating of the ash trees in AshY-positive and AshY-negative plots. Other disease and insect problems were common but were not considered to be major causes of crown dieback. The primary cause of crown dieback of ash in the Midwest is unknown.