Identification of <i>Armillaria</i> Species in the Chequamegon-Nicolet National Forest

Abstract

ABSTRACT.-Armillaria species were isolated from coniferous and deciduous overstory species in 17 of 22 stands in the Chequamegon area of the ChequamegonNicolet National Forest. Armillaria calvescens and A. sinapina were identified once each, and the remainder of the isolates were A. ostoyae. These findings are related to reports of Armillaria species from other areas of North America, particularly the western Great Lakes States, and to the potential role of Armillaria root disease in the Chequamegon. The Chequamegon area of the Chequamegon-Nicolet National Forest in northwestern Wisconsin covers 348,000 hectares, nearly 90 percent of which are classified as timberland (Haugen et al. 1998). In addition to wood and wood products, the lands are managed for wildlife habitat and numerous forms of recreation. Beginning in the late 1980s, USDA Forest Service personnel observed tree mortality and decline in some areas of the Chequamegon. Armillaria root disease, important in several areas of North America (Bruhn et al. 2000, Lundquist 2000, Mallett and Maynard 1998, McLaughlin 2001b, Morrison et al. 2001, Rizzo and Slaughter 2001, was suspected of contributing to these observed declines, but no mycological investigations had been done in this area.The objectives of this study were to identify the species of Armillaria present in the Chequamegon, especially in declining stands, and to relate these findings to previously collected information about Armillaria, particularly in the western Great Lakes States, but also in other areas of North America. This is the first step in assessing the role of these fungi in the Chequamegon forest. MATERIALS AND METHODSStands with dead and dying trees were selected first because the presence of Armillaria species was strongly suspected, and other stands were selected to represent the major overstory species of the forest. The root collars, butts, and one meter of lateral roots of recently killed or declining trees were examined for signs (mycelial fans or rhizomorphs) of Armillaria. The soil was carefully removed from around the base and lateral roots of these trees, and small areas of bark were lifted or peeled back. In stands where dying or declining trees were not observed, stumps and snags were examined. Samples of roots, root collars, and butts harboring Armillaria-like mycelial fans, rhizomorphs, or white stringy rot were collected for isolation, and the soil surrounding the sampled substrate was examined for rhizomorphs, which were collected if present. Host species, substrate type, and diameter at 1.3 m or at ground level, for trees and stumps, respectively, along with the location and form (fan, rhizomorph, decayed wood) of Armillaria observed were recorded for each sample. Overall condition of the tree, and the presence of decay, other fungi, and insect or disease problems were also noted. One or two samples for isolation were collected per stand. Sampled materials were placed in paper bags and stored in a cooler while traveling (1 to 2 days), then placed in cold storage (4 C...

Forest Life Under Control of Microbial Life

“…Disease symptoms first appear on immature leaves, leaf petioles, and nut shucks as small, olive-green spots that turn black. Leaf infections do not cause serious defoliation (Kromroy 2004).…”